Role of β2 Integrins in the Binding of Thymocytes to Rat Thymic Macrophages

A role of β2 integrins and one of their ligands, ICAM-1, in thymic macrophage (TMF)/thymocyte interactions was studied. TMF were isolated as adherent cells from 4-day old culture of thymic-cell suspensions either from normal or hydrocortisone-treated rats. Adherent cells were 94-98% positive with ED1 (a pan-macrophage marker). The majority of them (75-95%) expressed the CD11b and CD18 molecules, and 60-70% expressed CD54 (ICAM-1). A low proportion of TMF (10-20%) expressed CDlla (LFA-1). The expression of all these antigens was upregulated by IFN-α and TNF-α. The effect of these mAbs on TMF/thymocyte binding was studied using a simple rosette assay by incubating unstimulated or IFN-γ or TNF-α stimulated TMF, grown on microscopic slides with resting or ConA +IL-2 activated thymocytes. It was found that LFA-1/CD18 and ICAM-1 play a significant role in the TMF/thymocyte adhesion. In addition, a LFA-l-dependent/ICAM- 1-independent adhesion pathway was observed, suggesting that LFA-1 might use another ligand. The inhibitory effect of anti-CD18 mAb (WT-3) was higher than the effect of anti-LFA-1 mAb (WT-1) and was a consequence of blocking the CD18 chain both on thymocytes and TMF. No significant difference in the expression and function of adhesion molecules was found between TMF obtained from normal or hydrocortisone-treated rats. The involvement of CD1 1b in these processes was of lesser importance than the role of the CD11a molecule. By using mAbs to different epitopes of the CD11b molecule, such as OX-42 (anti-CD11b/CD11c), ED7, and ED8 (anti-CD11b), it was found that they were either slightly or moderately inhibitory under certain experimental conditions or did not significantly modulate TMF/thymocyte binding. Oχ-42 was slightly stimulatory in some experiments. Cumulatively, these results show that 2 integrins play a significant role in TMF/thymocyte interactions and probably contribute to T-cell development in vivo.     

Developmental regulation of p53-dependent radiation-induced thymocyte apoptosis in mice

The production of T cell receptor αβ⁺ (TCRαβ⁺) T lymphocytes in the thymus is a tightly regulated process that can be monitored by the regulated expression of several surface molecules, including CD4, CD8, cKit, CD25 and the TCR itself, after TCR genes have been assembled from discrete V, D (for TCR-β) and J gene segments by a site-directed genetic recombination. Thymocyte differentiation is the result of a delicate balance between cell death and survival: developing thymocytes die unless they receive a positive signal to proceed to the next stage. This equilibrium is altered in response to various physiological or physical stresses such as ionizing radiation, which induces a massive p53-dependent apoptosis of CD4⁺CD8⁺ double-positive (DP) thymocytes. Interestingly, these cells are actively rearranging their TCR-α chain genes. To unravel an eventual link between V(D)J recombination activity and thymocyte radio-sensitivity, we analysed the dynamics of thymocyte apoptosis and regeneration following exposure of wild-type and p53-deficient mice to different doses of γ-radiation. p53-dependent radio-sensitivity was already found to be high in immature CD4⁻CD8⁻ (double-negative, DN) cKit⁺CD25⁺ thymocytes, where TCR-β gene rearrangement is initiated. However, TCR-αβ⁻CD8⁺ immature single-positive thymocytes, an actively cycling intermediate population between the DN and DP stages, are the most radio-sensitive cells in the thymus, even though their apoptosis is only partially p53-dependent. Within the DP population, TCR-αβ⁺ thymocytes that completed TCR-α gene recombination are more radio-resistant than their TCR-αβ⁻ progenitors. Finally, we found no correlation between p53 activation and thymocyte sensitivity to radiation-induced apoptosis.     

Epidermal Growth Factor Modulates Fetal Thymocyte Growth and Differentiation

In the present study, we used the fetal organ culture (FTOC) technique in order to study a putative effect of epidermal growth factor (EGF) on the thymus ontogeny. Functional EGF receptors and more recently the EGF molecule itself, respectively, on the membrane of epithelial components of thymic stroma and on a few thymocytes in adult thymus, had been reported in the literature. We could observe a dose-dependent decrease in cellularity and a progressive retention of thymocytes in the double-negative (CD4^-/CD8^-) stage of differentiation when exogenous EGF was added. Epidermal growth factor interfered with both fetal stroma growth and thymocyte development at a precise moment, that is, in the passage from double-negative to the double-positive (CD4⁺/CD8⁺) stage. After a 7-day FTOC in the presence of EGF, most cells recovered were Thy-1.2⁺, c-kit⁺, TSA1^-/int, CD3^-, and one of CD44^high/CD25^int, CD44^-/CD25^int, or CD44^-/CD25^-. Some developed into γδTCR⁺ cells with a mature (CD3⁺) phenotype, but not into αβTCR⁺ thymocytes. It seems that EGF addition makes the cultures "nonpermissible" for αβTCR⁺ thymocyte generation. We report here the presence of a high Mr "EGF-like" molecule on the membrane of fetal thymocytes, which role in the observed effects is under investigation. Further biochemical characterization of this molecule is still required, because its presence was only evidenced on the basis of its antigenicity.     

Phenotypic characterization of T cells in bronchoalveolar lavage fluid (BALF) and peripheral blood of patients with diffuse panbronchiolitis; the importance of cytotoxic T cells

We investigated the contribution of T cells in diffuse panbronchiolitis (DPB) by identifying T cell subsets in BALF of 36 patients with DPB, before and after long-term treatment with macrolide antibiotics, and 16 healthy control subjects. The percentages of lymphocytes and CD3⁺γδ⁺ cells in BALF of DPB patients and control subjects were similar, but the absolute number of these cells was higher in DPB patients. Treatment resulted in a significant reduction in the absolute number of these cells. A further two-colour analysis of T cell subsets in BALF showed a significantly higher ratio and number of CD8⁺HLA-DR⁺ cells in DPB patients. Treatment resulted in a significant reduction of activated T cells. Most BALF CD8⁺ cells were CD8⁺CD11b⁻ cytotoxic T cells. The number of these cells in BALF of DPB patients (26.69 ± 5.86 × 10³/ml) was higher than the control (2.02 ± 0.38 × 10³/ml; P< 0.001), and a significant reduction was observed after treatment (7.69 ± 2.59 × 10³/ml; P< 0.01). The number of CD4⁺ cells was also higher in DPB patients than in controls, and most were CD4⁺CD29⁺ memory T cells. However, treatment did not influence the number of these cells. The number of lymphocytes, CD3⁺γδ⁺, CD8⁺CD11b⁻, CD8⁺HLA-DR⁺, and CD4⁺CD29⁺ cells was higher in patients with bacterial infection than in those without bacterial infection, and interestingly, macrolide therapy reduced the number of lymphocytes, CD3⁺γδ⁺, CD8⁺CD11b⁻ and CD8⁺HLA-DR⁺ cells, irrespective of bacterial infection. In peripheral blood, the percentage of CD8⁺HLA-DR⁺ cells was also higher in DPB patients than in healthy subjects, and significantly decreased after treatment. The percentage of CD8⁺CD11b⁻ cells in peripheral blood was similar in DPB patients and normal subjects, and treatment significantly reduced the percentage of these cells. Finally, the expression of the adhesion molecules CD11a/CD18 (α/β-chains of LFA-1) on lung CD3⁺ cells and CD49d (α-chain of VLA) on lung CD4⁺ cells was enhanced compared with that on peripheral blood in DPB patients. Our results suggest that elevation of memory T cells and activation of CD8⁺ cells, mainly cytotoxic T cells, in the airway lumen of DPB patients may contribute to chronic bronchial inflammation, possibly through up-regulation of adhesion molecules. Our findings also indicate that macrolide antibiotics may have a direct or indirect suppressive effect on cytotoxic T cells, and as such, reduce inflammation and improve clinical condition.     

Association of T cell dysfunction with the presence of IgG autoantibodies on CD4+ lymphocytes in haemophilia patients; results of a 10-year study

HIV induces progressive dysfunction followed by numerical depletion of CD4⁺ lymphocytes. IgG autoantibodies and gp120-containing immune complexes have been implicated in the pathogenesis of AIDS. We carried out a longitudinal study in 19 HIV^– and 72 HIV⁺ haemophilia patients over a 10-year period in order to investigate a possible relationship between the occurrence of autoantibodies and CD4⁺ lymphocyte changes. IgM, IgG, C3d and gp120 on the surface of CD4⁺ lymphocytes were determined in heparinized whole blood with flow cytometry and double-fluorescence. The in vitro response of autoantibody-coated cells was tested in cell cultures with concanavalin A (Con A), phytohaemagglutinin (PHA), pokeweed mitogen (PWM), anti-CD3 MoAb or pooled allogeneic stimulator cells (MLC). After a 10-year follow up, 12 of 71 HIV⁺ and 16 of 19 HIV^– haemophilia patients showed no evidence of immunoglobulins on circulating CD4⁺ lymphocytes. HIV^– haemophilia patients without autoantibodies had CD4⁺and CD8⁺ cell counts in the normal range (957 ± 642/μl and 636 ± 405/μl) and normal T cell responses in vitro (mean relative response (RR) ≥ 0.7). In contrast, HIV⁺ haemophilia patients showed immunological abnormalities which were associated with the autoantibody and immune complex load of CD4⁺ blood lymphocytes. HIV⁺ patients without autoantibodies had a mean CD4⁺ lymphocyte count of 372 ± 274/μl, a mean CD8⁺ lymphocyte count of 737 ± 435/μl, and normal T lymphocyte stimulation in vitro (mean RR ≥ 0.7). HIV⁺ patients with complement-fixing IgM on CD4⁺ lymphocytes had somewhat lower CD4⁺ (255 ± 246/μl, P= NS) and CD8⁺ (706 ± 468/μl, P= NS) lymphocyte numbers, and also normal T lymphocyte stimulation (mean RR ≥ 0.7) in vitro. However, patients with complement-fixing IgG autoantibodies showed a strong decrease of CD4⁺ (150 ± 146/μl, P< 0.02) and CD8⁺ (360 ± 300/μl, P< 0.02) lymphocytes and impaired CD4⁺ lymphocyte stimulation in vitro with a mean RR of 0.5 ± 0.5 for Con A (P= NS), 0.7 ± 0.8 for PHA (P< 0.03), 0.4 ± 0.4 for PWM (P= NS), 0.8 ± 1.2 for anti-CD3 MoAb (P< 0.04) and 0.7 ± 1.0 for pooled allogeneic stimulator cells (P= 0.05). Patients with gp120-containing immune complexes on CD4⁺ blood lymphocytes demonstrated strongly decreased CD4⁺(25 ± 35/μl, P< 0.0001) and CD8⁺ (213 ± 212/μl, P< 0.006) lymphocyte counts as well as strongly impaired T lymphocyte responses in vitro upon stimulation with PHA (RR 0.2 ± 0.1, P < 0.02), PWM (RR 0.2 ± 0.2, P= 0.05), anti-CD3 MoAb (RR 0.1 ± 0.1, P< 0.04), and allogeneic stimulator cells (RR 0.2 ± 0.1, P< 0.02). These data led us to speculate that autoantibody formation against CD4⁺ lymphocytes is an important mechanism in the pathogenesis of AIDS. We hypothesize that autoantibodies against circulating CD4⁺ lymphocytes inhibit CD4⁺ cell function, especially the release of cytokines, and induce CD4⁺ cell depletion. The reduction and dysfunction of CD4⁺ lymphocytes may be responsible for the CD8⁺ cell depletion observed in HIV⁺ patients.     

Human Thymic Epithelial Cells in Serum-Free Culture: Nature and Effects on Thymocyte Cell Lines

Thymic epithelial cells (TEC) have been cultured for several months and/or for 4 to 5 transfers in a growth factor-defined serum-free medium without concurrent growth of other cell types. The use of monoclonal antibodies and αMAM-6 indicated that the majority of TEC were of medullary origin. The vast majority of cells were positive for LFA-3 and class I, and class II expression, was low or absent. Supernatants from the cultures were shown to contain IL-1ß, IL-6, and M-CSF. Coculture of cloned subpopulations of thymocytes and TEC showed effects of TEC and of secreted ILs on thymocyte proliferation. High percentages of TEC were able to bind DN, DP, or SP thymocyte populations, partly via CD2-LFA-3 adhesion. Thus, it is possible to culture TEC without unknown serum factors and with maintenance of functional activities.     

Role of Prolactin in the Recovered T-Cell Development of Early Partially Decapitated Chicken Embryo

Although different experimental approaches have suggested certain regulation of the mammalian immune system by the neuroendocrine system, the precise factors involved in the process are largely unknown. In previous reports, we demonstrated important changes in the thymic development of chickens deprived of the major neuroendocrine centers by the removal of embryonic prosencephalon at 33-38 hr of incubation (DCx embryos) (Herradón et al., 1991; Moreno et al., 1995). In these embryos, there was a stopping of T-cell maturation that resulted in an accumulation of the most immature T-cell subsets (CD4^-CD8^- cells and CD4^-CD8^1o cells) and, accordingly, in decreased numbers of DP (CD4⁺CD8⁺) thymocytes and mature CD3⁺TcRαβ ⁺ cells, but not CD3⁺TcRγδ lymphocytes. In the present work, we restore the thymic histology as well as the percentage of distinct T-cell subsets of DCx embryos by supplying recombinant chicken prolactin, grafting of embryonic pituitary gland, or making cephalic chick-quail chimeras. The recovery was not, however, whole and the percentage of CD3⁺TcRαβ thymocytes did not reach the normal values observed in 17-day-old control Sham-DCx embryos. The results are discussed on the basis of a key role for prolactin in chicken T-cell maturation. This hormone could regulate the transition of DN (CD4^-CD8^-) thymocytes to the DP (CD4⁺CD8⁺) cell compartment through its capacity for inducing IL-2 receptor expression on the former.     

Appearance and Maturation of T-Cell Subsets During Rat Thymus Ontogeny

In previous papers, we have described the ontogenetical development of thymic stromal-cell components (epithelium, macrophages, dendritic cells) of Wistar rats. Here, we correlate those results with the maturation of rat T-cell precursors along the fetal and postnatal life. First T-cell precursors, which colonize the thymus anlage around days 13-14 of gestation, largely express CD45, CD43, CD53, and Thy 1 cell markers, and in a lesser proportion the OX22 antigen. Rat CD3^-CD4^-CD8^- thymocytes present in the earliest stages of gestation could be subdivided in three major cell subpopulations according to the CD44 and CD25 expression: CD44^-/+CD25^- → CD44⁺CD25⁺ → CD44⁺CD25^- On fetal days 17-18, a certain proportion of CD4^-CD8^-cells weakly,express the TcRβ chain, in correlation with the appearance of the first immature CD4^-CD8⁺ thymocytes. This cell subpopulation, in progress to the CD4⁺CD8⁺ stage, upregulates CD8α before the CD8β chain, expresses the CD53 antigen, and exhibits a high proliferative rate. First mature thymocytes arising from the DP (CD4⁺CD8⁺) cells appear on fetal days 20-21. Then, the CD4⁺:CD8⁺ cell ratio is ≤1 changing to adult values (2-3) just after birth. Also, the percentage of VβTcR repertoire covered in adult thymus is reached during the postnatal period, being lower during the fetal life. Finally, in correlation with the beginning of thymocyte emigration to the periphery a new wave of T-cell maturation apparently occurs in the perinatal rat thymus.     

Early Deletion and Late Positive Selection of T-Cells Expressing a Male-Specific Receptor in T-Cell Receptor Transgenic Mice

The ontogeny of T cells in T-cell receptor (TCR) transgenic mice, which express a transgenic αβ heterodimer, specific for the male (H-Y) antigen in association with H-2D^b, was determined. The transgenic α chain was expressed on about 10% of the fetal thymocytes on day 14 of gestation. About 50% of day-15 fetal thymocytes expressed both α and β transchains and virtually all fetal thymocytes expressed the transgenicαβ heterodimer by day 17. The early expression of the transgenic TCR on CD4^-8^- thymocytes prevented the development of γδ cells, and led to accelerated growth of thymocytes and an earlier expression of CD4 and CD8 molecules. Up to day 17, no significant differences in T-cell development could be detected between female and male thymuses. By day 18 of gestation, the male transgenic thymus contained more CD4^-8^- thymocytes than the female transgenic thymus. The preponderance of CD4^-8^- thymocytes in the male transgenic thymus increased until birth and was a consequence of the deletion of the CD4⁺8⁺ thymocytes and their CD4^-8⁺ precursors. By the time of birth, the male transgenic thymus contained half the number of cells as the female transgenic thymus. The deletion of autospecific precursor cells in the male transgenic mouse began only at day 18 of gestation, despite the fact that the ligand could already be detected by day 16.The preferential accumulation of CD4^-8⁺ T cells, which expressed a high density of the transgenic TCR, occurred only after birth and was .obvious in 6-week-old female thymus. These data support the hypothesis that the positive selection of T cells expressing this transgenic heterodimer may involve two steps, i.e., the commitment of CD4⁺8⁺ thymocytes to the CD4^-8⁺ lineage following the interaction of the transgenic TCR with restricting major histocompatibility molecules, followed by a slow conversion of CD4⁺8⁺ thymocytes into CD4^-8⁺ T cells.In normal mice, the precursors of CD⁺4⁺8 and single positive thymocytes have the CD4^-8^- CD3^-J11d⁺ (or M1/69 ⁺) phenotype. Because of the early expression of the transgenic αβ heterodimer, this population was not detected in adult transgenic mice. All CD4^-8^- M1/ 69⁺ cells expressed the transgenic receptor associated with CD3 and could be readily grown in media containing T-cell lectins and interleukin 2.     

Depletion of γδ+ T cells increases CD4+ FoxP3 (T regulatory) cell response in coxsackievirus B3-induced myocarditis

Coxsackievirus B3 (CVB3) causes severe myocarditis in BALB/c mice which depends upon CD4⁺ T helper type 1 [Th1; i.e. interferon-γ⁺ (IFN-γ⁺)] and γδ⁺ cells. Depleting γδ⁺ cells using anti-γδ antibody suppresses myocarditis and CD4⁺ IFN-γ⁺ cell numbers in the spleen and heart of infected mice while increasing CD4⁺ FoxP3⁺ cells. Mice deficient in γδ⁺ cells have increased numbers of naïve (CD44^lo CD62L^hi) and fewer effector (CD44^hi CD62^lo) memory CD4⁺ cells than infected γδ⁺-cell-sufficient mice. Virus neutralizing antibody titres are not significantly different between γδ⁺ T-cell-sufficient and -deficient animals. To confirm that the memory cell response differs in acutely infected mice lacking γδ⁺ cells, CD4⁺ cells were purified and adoptively transferred into naïve recipients, which were rested for 4 weeks then infected with CVB3. Recipients given either 0·5 × 10⁶ or 1·0 × 10⁶ CD4⁺ from infected donors developed over twice the severity myocarditis and 10-fold less cardiac virus titre compared with recipients given equivalent numbers of CD4⁺ cells from infected and γδ⁺-cell-depleted donor animals. Additionally, to show that more functionally active T regulatory cells are present in γδ⁺ T-cell-depleted mice, CD4⁺ CD25⁺ and CD4⁺ CD25⁻ cells were isolated and adoptively transferred into infected recipients. Mice receiving CD4⁺ CD25⁺ cells from γδ⁺ T-cell-depleted donors developed significantly less myocarditis and CD4⁺ Th1 cell responses compared with mice receiving equal numbers of CD4⁺ CD25⁺ cells from infected γδ⁺ T-cell-sufficient animals. This study shows that γδ⁺ cells promote CD4⁺ IFN-γ⁺ acute and memory responses by limiting FoxP3⁺ T regulatory cell activation.     

Increased numbers of CD5+ B cells and T cell receptor (TCR) γδ+ T cells are associated with younger age of onset in rheumatoid arthritis (RA)

Patients presenting with RA before the age of 45 years (younger onset) are known to have more aggressive disease compared with patients presenting after the age of 65 years (older onset). Coordinated expansion of circulating CD5⁺ B cell and TCR γδ⁺ T cell levels has been reported in patients with RA. This study assesses the peripheral blood levels of these two cell types in RA patients with younger and older onset of disease. CD5⁺ B cell levels were significantly elevated in the younger onset RA group (26·6 ± 4·5%) compared with the older onset RA group (14·2 ± 1·2%; P <0·01). TCR γδ⁺ T cell levels were also significantly raised in the young patients (4·0 ± 0·9%) compared with elderly patients (1·6 ± 0·2%; P <0·01). T cell levels (CD3⁺) were similar in both groups (young 66·4 ± 3·3%; old 74·3 ± 3·4% (mean ± s.e.m.); NS). Total B cell levels (CD19⁺) were also similar in these groups (7·7 ± 0·7% versus 8·9 ± 1·8%; NS). A significant positive correlation was observed between the CD5⁻ B and TCR γδ⁺ T cell types in the patients (r = 0·72, P <0.05). Compared with age-matched normal controls, the younger onset patients had similar CD5⁺ B cell and TCR γδ⁺ T cell levels to the elderly controls (CD5⁺ B cells 30·2 ± 3·0%; TCR γδ⁺ T cells 3·0 ± 0·8%). Conversely, older onset RA patients had CD5⁺ B cell levels similar to the young controls (12·3 ± 1·9%). Spontaneous in vitro synthesis of immunoglobulins (IgM, IgA and IgG) and rheumatoid factors (IgM and IgA isotypes) were not significantly different in both patient groups. The coordinate expansion of circulating CD5⁺ B cells and γδ⁺ T cells seen in patients with RA presenting before 45 years of age and not after 65 years of age may suggest a potential role for these cells in more aggressive disease states.     

Role of Thromboxane A2 in the Induction of Apoptosis of Immature Thymocytes by Lipopolysaccharide

Lipopolysaccharide (LPS) causes apoptotic deletion of CD4⁺ CD8⁺ thymocytes, a phenomenon that has been linked to immune dysfunction and poor survival during sepsis. Given the abundance of thromboxane-prostanoid (TP) receptors in CD4⁺ CD8⁺ thymocytes and in vitro evidence that thromboxane A₂ (TXA₂) causes apoptosis of these cells, we tested whether enhanced generation of TXA₂ plays a role in LPS-induced thymocyte apoptosis. Mice injected with 50 μg of LPS intraperitoneally displayed a marked increase in generation of TXA₂ and prostaglandin E₂ in the thymus as well as apoptotic deletion of CD4⁺ CD8⁺ thymocytes. Administration of indomethacin or rofecoxib inhibited prostanoid synthesis but did not affect thymocyte death. In contrast, thymocyte apoptosis in response to LPS was significantly attenuated in TP-deficient mice. These studies indicate that TXA₂ mediates a portion of apoptotic thymocyte death caused by LPS. The absence of an effect of global inhibition of prostanoid synthesis suggests a complex role for prostanoids in this model.     

Interferon‐γ‐ and glucocorticoid‐mediated pathways synergize to enhance death of CD4+ CD8+ thymocytes during Salmonella enterica serovar Typhimurium infection

Thymic atrophy is known to occur during infections; however, there is limited understanding of its causes and of the cross-talk between different pathways. This study investigates mechanisms involved in thymic atrophy during a model of oral infection by Salmonella enterica serovar Typhimurium (S. typhimurium). Significant death of CD4⁺ CD8⁺ thymocytes, but not of single-positive thymocytes or peripheral lymphocytes, is observed at later stages during infection with live, but not heat-killed, bacteria. The death of CD4⁺ CD8⁺ thymocytes is Fas-independent as shown by infection studies with lpr mice. However, apoptosis occurs with lowering of mitochondrial potential and higher caspase-3 activity. The amounts of cortisol, a glucocorticoid, and interferon-γ (IFN-γ), an inflammatory cytokine, increase upon infection. To investigate the functional roles of these molecules, studies were performed using Ifnγ^−/− mice together with RU486, a glucocorticoid receptor antagonist. Treatment of C57BL/6 mice with RU486 does not affect colony-forming units (CFU), amounts of IFN-γ and mouse survival; however, there is partial rescue in thymocyte death. Upon infection, Ifnγ^−/− mice display higher CFU and lower survival but more surviving thymocytes are recovered. However, there is no difference in cortisol amounts in C57BL/6 and Ifnγ^−/− mice. Importantly, the number of CD4⁺ CD8⁺ thymocytes is significantly higher in Ifnγ^−/− mice treated with RU486 along with lower caspase-3 activity and mitochondrial damage. Hence, endogenous glucocorticoid and IFN-γ-mediated pathways are parallel but synergize in an additive manner to induce death of CD4⁺ CD8⁺ thymocytes during S. typhimurium infection. The implications of this study for host responses during infection are discussed.     

Identification of a CD8α Dendritic Cell Subpopulation in Rat Spleen and Evaluation of Its OX-62 Expression

Rat spleen DC and bone marrow-derived DC were isolated and characterized by morphology and flow cytometry. We found a CD8α⁺ DC subpopulation representing 19–48% (27.4 ± 12.0) of total spleen DC. The OX-62 expression on total spleen DC was 41–59% (51.8 ± 7.5). Myeloid bone marrow-derived DC were negative for CD8α and OX-62. We demonstrated the coexpression of CD8α and OX-62 molecules, at least in a portion CD8α⁺ spleen DC. Both CD8α⁺ and CD8α⁻ spleen DC subpopulations separated by MACS were able to induce an in vivo primary immune response to OVA. The immune response induced by the CD8α⁻ DC subpopulation was higher (P < 0.05). We identified a CD8α⁺ DC subpopulation in rat spleen less effective in inducing an immune response than CD8α⁻ DC. Moreover, our results suggest the presence of DC subpopulations with different lineages in DC preparations based on OX-62 expression.     

Blood monocyte activation in rheumatoid arthritis: increased monocyte adhesiveness, integrin expression, and cytokine release

Infiltration of the synovium by mononuclear cells, namely lymphocytes and monocytes, is one of the main features of rheumatoid arthritis (RA) and is considered to be responsible for the development of the disease. In this study in 31 consecutive patients with RA, we investigated whether peripheral blood monocytes exhibited markers of cellular activation related to cell migration. Using flow cytometry with the respective specific antibodies, we studied the expression of integrins CD11a, CD11b, CD11c, CD49d (VLA-4), and CD49e (VLA-5) on monocytes from patients with RA and from normal (N) subjects. IL-1β, IL-6, and tumour necrosis factor-alpha (TNF-α) production by cultured monocytes was measured by immunoassay. Adhesiveness of monocytes was studied on various surfaces (plastic, human fibronectin, gelatin-coated plasma, subendothelial matrix) and on cultured endothelial cells under basal conditions or after stimulation by IL-1β. An increased number of CD14⁺ monocytes (Mo) from RA patients expressed the CD11b molecule (RA Mo = 90·3%, N Mo = 83·4%, P < 0·005). The expression of CD11b on CD14⁺ monocytes was significantly increased in RA patients (median fluorescence intensity (FI): RA Mo = 145 (range 80–466) units; normal Mo = 95 (range 24–164) units; P < 0·003). Production of extracellular IL-1β and IL-6 by RA monocytes was significantly enhanced compared with monocytes from normal subjects (IL-1β: RA = 2·65 ± 0·91 ng/ml versusN = 1·35 ± 0·85 pg/ml, P < 0·05; IL-6: RA = 4·83 ± 0·90 ng/ml versusN = 2·40 ± 0·95 ng/ml, P < 0·05). Compared with normal monocytes, RA monocytes exhibited increased adhesion to the various surfaces studied (plastic, P < 0·01; fibronectin, P < 0·01; and gelatin-coated normal or RA plasma, P < 0·01) as well as to unstimulated (P < 0·01) and IL-1β-stimulated endothelial cells (IL-1β for 4 h, P < 0·05; IL-1β for 24 h, P < 0·05). In our study, blood monocytes from RA patients exhibited features of activation related to cell adhesion.     

Role of γδ T lymphocytes in the development of Behçet's disease

Phenotypic and functional properties of γδ T cells, which play an important role in mucocutaneous immunity, were examined to elucidate whether immunological abnormality in Behc¸et's disease may be related to a specific T cell population. We found that CD45RA⁺Vγ9⁺Vδ2⁺γδ T cells, which constitute a minor population of γδ T cells in healthy individuals, were increased in number in Behc¸et's disease irrespective of disease activity. This CD45RA⁺ subset of γδ T cells in the active, but not inactive, phase of this disease expressed IL-2Rβ and HLA-DR, suggesting that they are activated in vivo in active Behc¸et's disease. In addition, the CD45RA⁺γδ T cells produced extreme amounts of tumour necrosis factor and contained perforin granules. These data indicate that a phenotypically distinct subset of γδ T cells, CD45RA⁺CD45RO⁻Vγ9⁺Vδ2⁺, may contribute to immunological abnormalities which may lead to complexity of pathophysiology in Behc¸et's disease.     

Expression of Adhesion Molecules and CD28 on T Lymphocytes during Human Immunodeficiency Virus Infection

Adhesion molecules, which play a major role in lymphocyte circulation, have not been well characterized in human immunodeficiency virus (HIV) infection. T-lymphocyte populations, including CD3, CD4, CD28, and adhesion molecules (L selectin, LFA-1, VLA-4, and ICAM-1) were measured by flow cytometry in a cross-sectional study of 100 HIV-infected and 49 HIV-seronegative adults. HIV-infected adults had lower numbers of CD3⁺ lymphocytes expressing L selectin (P < 0.0001) and VLA-4 (P < 0.01) and higher numbers of CD3⁺ lymphocytes expressing LFA-1^bright (P < 0.002) than did HIV-negative adults. By CD4⁺-lymphocyte count category (>500, 200 to 500, or <200 cells/μl), HIV-infected adults with more advanced disease had lower percentages of CD3⁺ lymphocytes expressing L selectin and VLA-4 and higher percentages of CD3⁺ lymphocytes expressing LFA-1. The percentages of CD3⁺ CD28⁺ lymphocytes and of CD3⁺ L selectin⁺ lymphocytes were positively correlated (Spearman coefficient = 0.86; P < 0.0001), and the percentage of CD3⁺ CD28⁺ lymphocytes and the CD3⁺ LFA-1^bright lymphocyte/CD3⁺ LFA-1^dim lymphocyte ratio were negatively correlated (Spearman coefficient = −0.92; P <0.00001). The results of this study suggest that HIV infection is associated with altered expression of adhesion molecules.     

Effect of thymosin alpha-1 on subpopulations of Th1, Th2, Th17, and regulatory T cells (Tregs) in vitro

Thymosin alpha 1 (Tα1) has been shown to have beneficial effects on numerous immune system parameters, but little is known about the effects of Tα1 on patients with gastric carcinoma. The objective of this study was to determine the effect of Tα1 on subpopulations of Th1, Th2, Th17, and regulatory T cells (Tregs) in vitro, and to evaluate its efficacy as an immunoregulatory factor in patients with gastric carcinoma. We compared the effect of Tα1 on the frequency of CD4⁺ and CD8⁺ T cells, especially the CD4⁺CD25⁺Foxp3⁺ Tregs in peripheral blood mononuclear cells (PBMCs) from gastric carcinoma patients (N = 35) and healthy donors (N = 22). We also analyzed the changes in the proliferation of PBMCs in response to treatment with Tα1, and examined the production of Th1, Th2, and Th17 cytokines by PBMCs and tumor-infiltrating lymphocytes. The treatment of PBMCs from gastric cancer patients, with Tα1 (50 µg/mL) alone increased the percentage of CD4+CD25+Foxp3+ (suppressive antitumor-specific Tregs) from 1.68 ± 0.697 to 2.19 ± 0.795% (P < 0.05). Our results indicate that Tα1 increases the percentage of Tregs and IL-1β, TNF-α, and IL-6 in vitro.     

Differential expression of cell adhesion molecules in the functional compartments of lymph nodes and tonsils

Aims—To analyse the topographical distribution of adhesion molecules involved in lymphocyte recirculation in human lymph nodes and tonsils. The study focused on the expression of LECAM-1 (CD62L), VLA-α4 (CD49d), VLA-β1 (CD29), LFA-1 αL (CD11a), LFA-β2 (CD18), VCAM-1 (CD106), ICAM-1 (CD54), and H-CAM (CD44).     

T cell clones from a Sjögren's syndrome salivary gland biopsy produce high levels of IL-10

Sjögren''s syndrome (SS) is characterized by a focal periductal salivary gland infiltrate consisting mainly of T and B lymphocytes. Most of the T cells bear the memory of CD4⁺ Th-1-like phenotype and express high levels of class II, though CD8⁺ cells are also present. We have studied 17 labial salivary gland and 15 peripheral blood T cell clones from a patient with primary SS. The tissue clones were 71% CD8⁺ and 29% CD4⁺, and the peripheral blood-derived clones were 60% CD8⁺ and 40% CD4⁺. The CD4⁺ T cell clones from both the salivary gland and autologous peripheral blood were of the Th1 phenotype, in that they produced interferon-gamma (IFN-γ) and IL-2 but very little IL-4 after 24 h stimulation with phorbol myristate acetate and anti-CD3 antibody. The salivary gland-derived CD4⁺ clones produced 15 times more IL-10 (7·92 ng/ml) than peripheral blood-derived CD4⁺ clones (0·52 ng/ml, P≤0·02). The tissue CD8⁺ clones produced 1·2 times (P<0·04) more IFN-γ and CD4⁺ clones produced 3·5 times less IL-2 (P<0·02) than the respective PBM-derived clones. The accumulation of Th1-type cells producing high levels of IL-10 in the salivary gland suggests a specific immunoregulatory function at the site of inflammation in SS.