Cultivation of Virulent Treponema pallidum in Tissue Culture

In a series of seven experiments, the virulent Nichols strain of Treponema pallidum was shown to attach and replicate on the surface of tissue culture cells of cottontail rabbit epithelium (Sf1Ep) growing in conventional monolayer cultures under an atmosphere of 1.5% oxygen. Five days after inoculation of 10⁶T. pallidum, the number of treponemes had increased to between 8 × 10⁶ and 2.59 × 10⁷. The viability of harvested organisms ranged from 86 to 97%. The number of T. pallidum continued to increase, generally reaching a plateau between days 9 and 12 of incubation, with increases ranging up to 100-fold and averaging 49-fold. There appeared to be a ceiling of multiplication of about 2 × 10⁸ irrespective of the inoculum, which ranged from 10⁶ to 10⁸T. pallidum. Concurrent deoxyribonucleic acid assays were performed on the cultures containing T. pallidum to obtain further evidence of replication. Significant increases in treponemal deoxyribonucleic acid were observed when the inocula ranged from 10⁶ to 10⁷, with the greatest increases, as might be expected, being in the former group. There was also excellent correlation in the amount of deoxyribonucleic acid per treponeme; the averages for the 10⁶, 2.5 × 10⁶, and 10⁷ groups were 3.46 × 10⁻¹⁴, 3.28 × 10⁻¹⁴, and 2.79 × 10⁻¹⁴ g per treponeme, respectively (3.14 ± 0.72 × 10⁻¹⁴ g per treponeme). In each experiment, organisms were harvested from the group inoculated with 10⁶T. pallidum after 7 days of incubation to test for virulence. In all instances, the organisms were virulent; erythematous, indurated, treponeme-containing lesions were produced from an average of six to seven organisms. Scanning electron microscopy revealed that during the course of replication many microcolonies of treponemes formed on the surface of the cells.     

Colonization of Teeth in Humans by Streptococcus mutans as Related to Its Concentration in Saliva and Host Age

The relationship of the salivary concentration of Streptococcus mutans and host age to the colonization of this organism on erupting teeth was studied in humans. Plaques were obtained from fissures and buccal surfaces of erupting permanent first and second molars of children 6 to 7 and 11 to 14 years old, respectively. In subjects of both age groups with salivary S. mutans concentrations below 5 × 10² colony-forming units per ml, the organism was detected on only a few of the tooth surfaces; at concentrations of 5 × 10² to 4.9 × 10⁴ colony-forming units per ml more than half of the surfaces and at concentrations of 5 × 10⁴ colony-forming units per ml or higher most of the surfaces were colonized by S. mutans. The frequency of detection and concentration of S. mutans in plaque as well as its concentration in saliva were higher in the case of the older children. However, when younger and older children with similar salivary S. mutans concentrations were compared, S. mutans was more frequently isolated from plaque from older children only in the case of children with below 5 × 10² colony-forming units per ml of saliva. Eleven of the 64 children studied had low or undetectable S. mutans levels in plaque and saliva. The salivary S. mutans levels of the parents of these children were lower than those of parents of a group of children with normal oral S. mutans levels.     

Separation and characterization of cardiac antigen proteins

An attempt has been made to purify and characterize the protein antigens related to autoimmune carditis in the heart extract of albino rats by ammonium sulphate fractionation, molecular sieve gel filtration and polyacrylamide gel electrophoresis. The heart extract of albino rat at pH 7·0 contains at least nine proteins out of which three are antigenic in rabbits and have been termed as CA I, II and III. These antigens can be purified by ammonium sulphate fractional precipitation followed by Sephadex G-100 gel filtration. Their molecular weights were 6·6 (±2) × 10⁴, 2·8 (±0·85) × 10⁴, 4·8 (±1·5) × 10⁴ Daltons. A fourth antigen (CA IV) detected is probably polysaccharide.     

The equilibrium constants of anti-D immunoglobulin preparations made from pools of donor plasma

Estimates have been made of the value of the equilibrium constant and of the heterogeneity index of the reaction between anti-D and Rh positive red cells, using anti-D immunoglobulin preparations made from pools of donor plasma. The values of the equilibrium constant all fell within the range 1×10⁸ to 10×10⁸ 1/mole, and in eighteen of the twenty-five samples the values fell within the narrow range of 2×10⁸ to 4×10⁸ 1/mole. Estimates of the value of the heterogeneity index varied from 0.5 to 0.8. Calculations made using these values of the equilibrium constant indicate that if 200 μg of anti-D from each preparation were injected into an Rh-negative recipient with approximately 3 ml of R₁r cells in the circulation, between 8 and 28 per cent (average 17 per cent) of the D antigen sites on the red cells would be bound by anti-D if equilibrium conditions were reached.     

Disseminated Intravascular Coagulation Induced with Leukocyte Procoagulant

The procoagulant activity of rabbit peritoneal leukocytes significantly increased when the leukocytes were incubated in suspension cultures at 37 C for 24 hours. Intravenous infusions of Iysates of 232 × 10⁶ rabbit leukocytes which had been incubated in cultures at 37 C for 24 hours produced disseminated intravascular coagulation and vasculitis involving the pulmonary arteries in normal rabbits. Intraaortic infusions of lysates of 230 × 10⁶ similarly incubated leukocytes produced renal thrombosis and renal cortical necrosis in normal rabbits. These observations suggest that the procoagulant of granulocytic leukocytes could play a role in the generalized Shwartzman reaction and other syndromes of disseminated intravascular coagulation.     

Efficacy and Immunogenicity of Single-Dose AdVAV Intranasal Anthrax Vaccine Compared to Anthrax Vaccine Absorbed in an Aerosolized Spore Rabbit Challenge Model

AdVAV is a replication-deficient adenovirus type 5-vectored vaccine expressing the 83-kDa protective antigen (PA83) from Bacillus anthracis that is being developed for the prevention of disease caused by inhalation of aerosolized B. anthracis spores. A noninferiority study comparing the efficacy of AdVAV to the currently licensed Anthrax Vaccine Absorbed (AVA; BioThrax) was performed in New Zealand White rabbits using postchallenge survival as the study endpoint (20% noninferiority margin for survival). Three groups of 32 rabbits were vaccinated with a single intranasal dose of AdVAV (7.5 × 10⁷, 1.5 × 10⁹, or 3.5 × 10¹⁰ viral particles). Three additional groups of 32 animals received two doses of either intranasal AdVAV (3.5 × 10¹⁰ viral particles) or intramuscular AVA (diluted 1:16 or 1:64) 28 days apart. The placebo group of 16 rabbits received a single intranasal dose of AdVAV formulation buffer. All animals were challenged via the inhalation route with a targeted dose of 200 times the 50% lethal dose (LD₅₀) of aerosolized B. anthracis Ames spores 70 days after the initial vaccination and were followed for 3 weeks. PA83 immunogenicity was evaluated by validated toxin neutralizing antibody and serum anti-PA83 IgG enzyme-linked immunosorbent assays (ELISAs). All animals in the placebo cohort died from the challenge. Three of the four AdVAV dose cohorts tested, including two single-dose cohorts, achieved statistical noninferiority relative to the AVA comparator group, with survival rates between 97% and 100%. Vaccination with AdVAV also produced antibody titers with earlier onset and greater persistence than vaccination with AVA.     

Quantitative Detection of Circulating Nucleophosmin Mutations DNA in the Plasma of Patients with Acute Myeloid Leukemia

Objective: The aim of this study was to quantify the copies of circulating nucleophosmin (NPM) mutations DNA in the plasma of patients with acute myeloid leukemia (AML) and to explore the association of circulating NPM mutation levels with clinical characteristics.Design and Methods: The presence of NPM mutations in 100 Chinese patients newly diagnosed with AML were identified by RT-PCR and sequencing analysis. Copies of circulating NPM mutation A (NPM mut.A) DNA in the plasma of mutation-positive cases were quantified by real-time quantitative PCR (qRT-PCR). Furthermore, the association of circulating NPM mutation levels and clinical characteristics was analyzed.Results: NPM mutations were identified in 37 of the 100 patients and all cases were NPM mut.A. The circulating NPM mut.A levels ranged from 0.35×10⁸ copies/ml to 6.0×10⁸ copies/ml in the 37 mutation-positive cases. The medium and quartile M (P25, P75) of the circulating NPM mut.A levels in patients classified as M2, M4 and M5 morphological subtypes were 1.35×10⁸ (0.76×10⁸, 1.91×10⁸) copies/ml, 1.81×10⁸ (1.47×10⁸, 2.2×10⁸) copies/ml and 2.50×10⁸ (2.42×10⁸, 3.05×10⁸) copies/ml, respectively. Circulating NPM mut.A levels were significantly higher in patients with the M5 subtype of AML compared to patients with the M2 and M4 subtypes (p=0.000, p=0.046). In addition, circulating NPM mut.A copies were significantly associated with a higher white blood cell count, platelet count and bone marrow blast percentage (p<0.05).Conclusion: Our results suggest that circulating NPM mutations DNA assay serves as a complementary to the routine investigative protocol of NPM-mutated leukemia.     

A Murine Model of Renal Abscess Formation

We developed a murine model of kidney abscess by direct renal injection of either Escherichia coli (1 × 10⁶ to 7 × 10⁶ organisms) or sterile medium. Bacterial infection produced renal abscesses, bacteremia, and late-onset leukocytosis in all animals. Controls were unaffected. This model may be useful for the study of various sequelae of kidney infection.     

A study of clonal transfer in rabbits immunized with Salmonella abortus-equi

We have attempted to reconstitute 750 R-irradiated New Zealand white rabbits with lymphoid cells from a donor immunized with Salmonella abortus-equi (S.a-e). Antibodies to S.a-e in the serum of such reconstituted recipients, have been principally studied by the IEF technique. Lymph node or bone marrow cells failed to reconstitute the irradiated recipients which began to produce antibodies to S.a-e as they recovered from irradiation (from 2 to 3 weeks after radiation exposure). Attempts made with spleen cells were sufficiently successful to permit the detection, during 3 weeks after cell transfer, of donor allotypes and donor idiotypes in recipient sera. One week after cell transfer, the pI spectra of antibodies to S.a-e in these sera were very heterogeneous and showed the same patterns of bands on IEF as the donor antibodies. The two or three clonal antibodies recognized by the anti-idiotypic serum did not segregate in the various recipients. This heterogeneity must be the reflection of the large number of spleen cells (2.5 × 10⁷–1 × 10⁸) we were obliged to use in order to find suitable amounts of donor idiotypes in recipient sera. As the rabbits were not inbred, donor cells were finally rejected by the hosts, 3 or 4 weeks after cell transfer.

With such a system, selection of antibody-forming cell clones is a rare event. We have observed two cases out of a total of about hundred rabbits studied. These successful selections of restricted responses occurred in two out of four of the recipients of 5 × 10⁶ donor spleen cells. When dominance of a strong clone was established, rejection of donor cells seemed to be delayed (from 3 to 5 weeks). With these outbred rabbits, it was not possible to propagate the selected clones further than a second transfer generation.

Antibodies to S.a-e produced by irradiated rabbits used as controls (they received bacteria alone) showed, at the beginning of the recovery from irradiation (from 1 to 2 weeks after radiation exposure), very simple pI spectra as observed with neonatal rabbits during early steps of ontogeny of the antibody diversity.

     

Graft reaction in tissue culture: II. Quantification of the lytic action on mouse fibroblasts by rat lymphocytes sensitized on mouse embryo monolayers

A method for assaying the lytic action of large pyroninophilic cells (LPC) in cultures of rat lymphocytes on target fibroblasts in mouse embryo monolayers has been described. The basis of the assay was the labelling of fibroblasts with ⁵¹Cr. The rate of ⁵¹Cr release to the medium was found to be proportional to the number of LPC and expressed precisely the actual number of lysed fibroblasts. The lytic activity in LPC suspension was expressed by the lysis index which is the number of LPC per fibroblast lysed at 50 per cent lysis. A suspension of LPC collected 5–6 days after exposure of rat lymphocytes to the mouse monolayers showed a lysis index ranging from 0.7 to 1.3 after 16–48 hours of incubation. The lytic power of a culture was expressed by a value which was obtained by dividing the total number of LPC in a culture by the index. This determined the total number of fibroblasts lysed if the whole culture content were distributed among plates of test monolayer in such a way as to produce 50 per cent lysis in all the plates. Cultures started with 25 × 10⁶ to 30 × 10⁶ lymphocytes produced on the 5th and 6th day a lytic power of as high as 6 × 10⁶ to 12 × 10⁶ fibroblasts. The study has indicated that rats injected with horse serum and boosted 2 days prior to culturing were completely unable to produce graft reaction cultures. Lymphoid cells from non-boosted rats did generate LPC with lytic ability. A quantitative study of the specificity of the lytic reaction has indicated that LPC originated on C57BL/6 monolayers lysed much more strongly monolayers isologous to originator than C3H monolayers, and vice versa.     

Homozygosity analysis in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) may appear to be familial or sporadic, with recognised dominant and recessive inheritance in a proportion of cases. Sporadic ALS may be caused by rare homozygous recessive mutations. We studied patients and controls from the UK and a multinational pooled analysis of GWAS data on homozygosity in ALS to determine any potential recessive variant leading to the disease. Six-hundred and twenty ALS and 5169 controls were studied in the UK cohort. A total of 7646 homozygosity segments with length >2 Mb were identified, and 3568 rare segments remained after filtering ‘common'' segments. The mean total of the autosomal genome with homozygosity segments was longer in ALS than in controls (unfiltered segments, P=0.05). Two-thousand and seventeen ALS and 6918 controls were studied in the pooled analysis. There were more regions of homozygosity segments per case (P=1 × 10⁻⁵), a greater proportion of cases harboured homozygosity (P=2 × 10⁻⁵), a longer average length of segment (P=1 × 10⁻⁵), a longer total genome coverage (P=1 × 10⁻⁵), and a higher rate of these segments overlapped with RefSeq gene regions (P=1 × 10⁻⁵), in ALS patients than controls. Positive associations were found in three regions. The most significant was in the chromosome 21 SOD1 region, and also chromosome 1 2.9–4.8 Mb, and chromosome 5 in the 65 Mb region. There are more than twenty potential genes in these regions. These findings point to further possible rare recessive genetic causes of ALS, which are not identified as common variants in GWAS.     

The rabbit red cell antigen HgA and anti-HgA

The number of Hg^A sites on rabbit red cells was found to lie between 1.38 and 1.90 × 10⁵ per cell in heterozygotes (Hg^AHg^F) and between 3.0 and 3.8 × 10⁵ per cell in homozygotes (Hg^AHg^A).

The lowest concentration of IgG anti-Hg^A which could be detected using a `standard' indirect antiglobulin test was in the range 0.02–0.08 μg/ml.

The equilibrium constant of different examples of IgG anti-Hg^A lay between 0.5 and 1.56 × 10⁸1/mole.

The ability of different examples of IgG anti-Hg^A to bind complement varied widely: some examples produced macroscopic haemolysis after 1-hour incubation with rabbit complement; one example produced no haemolysis even when the sensitive ⁵¹Cr-release method was used and failed to sensitize red cells to agglutination by anti-C3. The rate of haemolysis produced by haemolytic anti-Hg^A was very much less than that produced by haemolytic human anti-A.

     

Differences in potential for selection of clindamycin-resistant mutants between inducible erm(A) and erm(C) Staphylococcus aureus genes

In staphylococci, inducible macrolide-lincosamide-streptogramin B (MLS_B) resistance is conferred by the erm(C) or erm(A) gene. This phenotype is characterized by the erythromycin-clindamycin “D-zone” test. Although clindamycin appears active in vitro, exposure of MLS_B-inducible Staphylococcus aureus to this antibiotic may result in the selection of clindamycin-resistant mutants, either in vitro or in vivo. We have compared the frequencies of mutation to clindamycin resistance for 28 isolates of S. aureus inducibly resistant to erythromycin and bearing the erm(C) (n = 18) or erm(A) (n = 10) gene. Seven isolates susceptible to erythromycin or bearing the msr(A) gene (efflux) were used as controls. The frequencies of mutation to clindamycin resistance for the erm(A) isolates (mean ± standard deviation, 3.4 × 10⁻⁸ ± 2.4 × 10⁻⁸) were only slightly higher than those for the controls (1.1 × 10⁻⁸ ± 6.4 × 10⁻⁹). By contrast, erm(C) isolates displayed a mean frequency of mutation to clindamycin resistance (4.7 × 10⁻⁷ ± 5.5 × 10⁻⁷) 14-fold higher than that of the S. aureus isolates with erm(A). The difference was also observed, although to a lower extent, when erm(C) and erm(A) were cloned into S. aureus RN4220. We conclude that erm(C) and erm(A) have different genetic potentials for selection of clindamycin-resistant mutants. By the disk diffusion method, erm(C) and erm(A) isolates could be distinguished on the basis of high- and low-level resistance to oleandomycin, respectively.     

Genome-wide association study with 1000 genomes imputation identifies signals for nine sex hormone-related phenotypes

Genetic factors contribute strongly to sex hormone levels, yet knowledge of the regulatory mechanisms remains incomplete. Genome-wide association studies (GWAS) have identified only a small number of loci associated with sex hormone levels, with several reproductive hormones yet to be assessed. The aim of the study was to identify novel genetic variants contributing to the regulation of sex hormones. We performed GWAS using genotypes imputed from the 1000 Genomes reference panel. The study used genotype and phenotype data from a UK twin register. We included 2913 individuals (up to 294 males) from the Twins UK study, excluding individuals receiving hormone treatment. Phenotypes were standardised for age, sex, BMI, stage of menstrual cycle and menopausal status. We tested 7 879 351 autosomal SNPs for association with levels of dehydroepiandrosterone sulphate (DHEAS), oestradiol, free androgen index (FAI), follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin, progesterone, sex hormone-binding globulin and testosterone. Eight independent genetic variants reached genome-wide significance (P<5 × 10⁻⁸), with minor allele frequencies of 1.3–23.9%. Novel signals included variants for progesterone (P=7.68 × 10⁻¹²), oestradiol (P=1.63 × 10⁻⁸) and FAI (P=1.50 × 10⁻⁸). A genetic variant near the FSHB gene was identified which influenced both FSH (P=1.74 × 10⁻⁸) and LH (P=3.94 × 10⁻⁹) levels. A separate locus on chromosome 7 was associated with both DHEAS (P=1.82 × 10⁻¹⁴) and progesterone (P=6.09 × 10⁻¹⁴). This study highlights loci that are relevant to reproductive function and suggests overlap in the genetic basis of hormone regulation.     

The secondary anti-erythrocte response of rabbit spleen cells stimulated in vitro

Suspensions of spleen cells from rabbits immunized to sheep erythrocytes and stimulated in vitro by the specific antigen produced high numbers of antibody-synthesizing cells. Several factors were found to affect secondary antigenic stimulation in vitro. The extent of the immune response elicited was a function of antigen concentration. Maximum was obtained by stimulation with 10⁴ to 10⁵ erythrocytes/10⁷ spleen cells; 10⁷ erythrocytes inhibited the response. The maximum usually occurred on days 4–6; glutamine increased the rate at which antibody-synthesizing cells appeared. It was found that the source of the normal serum supplement used in the growth medium markedly affected the results. Storage of rabbit serum reduced its efficacy; after 6 months storage at –10° little or no response was obtained. The addition of specific antiserum on days 1, 2 or 3 reduced the cellular response.

With cells from twenty-six rabbits tested 6–39 months after immunization, maxima of 1700–29,700 antibody-synthesizing cells/10⁷ spleen cells were attained. No relationship was evident between the time from immunization and the extent of the response. The activity of the extracellular antibody produced by the cells correlated roughly with the number of antibody-synthesizing cells. The antibody elicited in vitro was specific and stable on storage at –10° for 2 years. On the basis of sensitivity to 2-mercaptoethanol, it was a macroglobulin. Disc electrophoresis and identification of the haemolytic component showed that the antibody synthesized in vitro migrated with the γ-globulins, at the same rate as the active component in anti-erythrocyte rabbit serum.

     

Streptococcus sanguis-Induced Platelet Clotting in Rabbits and Hemodynamic and Cardiopulmonary Consequences

By mimicking hemostatic structural domains of collagen, Streptococcus sanguis (aggregation-positive phenotype; Agg⁺) induces platelets to aggregate in vitro. To test the hypothesis that aggregation occurs in vivo, S. sanguis (Agg⁺ or Agg⁻ suspension) was infused intravenously into rabbits. The extent of hemodynamic and cardiopulmonary changes and the fate of circulating platelets were Agg⁺ strain dose dependent. Within 45 to 50 s of the start of infusion, 40 × 10⁸ CFU of the Agg⁺ strain caused increased blood pressure. Thirty seconds after infusion, other changes occurred. Intermittent electrocardiographic abnormalities (13 of 15 rabbits), ST-segment depression (10 of 15 rabbits), and preventricular contractions (7 of 15 rabbits) manifested at 3 to 7 min, with frequencies dose dependent. Respiratory rate and cardiac contractility increased during this phase. Blood catecholamine concentration, thrombocytopenia, accumulation of ¹¹¹Indium-labeled platelets in the lungs, and ventricular axis deviation also showed dose dependency. Rabbits were unaffected by inoculation of an Agg⁻ strain. Therefore, Agg⁺ S. sanguis induced platelet aggregation in vitro. Platelet clots caused hemodynamic changes, acute pulmonary hypertension, and cardiac abnormalities, including ischemia.     

Isolation of Digital Dermatitis Treponemes from Hoof Lesions in Wild North American Elk (Cervus elaphus) in Washington State,USA

Since 2008, a large increase in the numbers of cases of lameness have been seen in wild North American elk (Cervus elaphus) from Washington State, USA. The most recent cases manifested as foot lesions similar both clinically and pathologically to those seen in digital dermatitis (DD) in cattle and sheep, a disease with a bacterial etiopathogenesis. To determine whether the same bacteria considered responsible for DD are associated with elk lameness, lesion samples were subjected to bacterial isolation studies and PCR assays for three phylogroups of relevant DD treponemes. The DD treponemes were isolated from lesional tissues but not from control feet or other areas of the diseased foot (including the coronary band or interdigital space), suggesting that the bacteria are strongly associated with DD lesions and may therefore be causal. In addition, PCR analysis revealed that all three unique DD treponeme phylotypes were found in elk hoof disease, and in 23% of samples, all 3 DD-associated treponemes were present in lesions. Sequence analysis of the 16S rRNA gene showed that the elk lesion treponemes were phylogenetically almost identical to those isolated from cattle and sheep DD lesions. The isolates were particularly similar to two of the three culturable DD treponeme phylotypes: specifically, the Treponema medium/Treponema vincentii-like and Treponema phagedenis-like DD spirochetes. The third treponeme culturable phylogroup (Treponema pedis), although detected by PCR, was not isolated. This is the first report describing isolation of DD treponemes from a wildlife host, suggesting that the disease may be evolving to include a wider spectrum of cloven-hoofed animals.     

Fine mapping of eight psoriasis susceptibility loci

Previous studies have identified 41 independent genome-wide significant psoriasis susceptibility loci. After our first psoriasis genome-wide association study, we designed a custom genotyping array to fine-map eight genome-wide significant susceptibility loci known at that time (IL23R, IL13, IL12B, TNIP1, MHC, TNFAIP3, IL23A and RNF114) enabling genotyping of 2269 single-nucleotide polymorphisms (SNPs) in the eight loci for 2699 psoriasis cases and 2107 unaffected controls of European ancestry. We imputed these data using the latest 1000 Genome reference haplotypes, which included both indels and SNPs, to increase the marker density of the eight loci to 49 239 genetic variants. Using stepwise conditional association analysis, we identified nine independent signals distributed across six of the eight loci. In the major histocompatibility complex (MHC) region, we detected three independent signals at rs114255771 (P=2.94 × 10⁻⁷⁴), rs6924962 (P=3.21 × 10⁻¹⁹) and rs892666 (P=1.11 × 10⁻¹⁰). Near IL12B we detected two independent signals at rs62377586 (P=7.42 × 10⁻¹⁶) and rs918518 (P=3.22 × 10⁻¹¹). Only one signal was observed in each of the TNIP1 (rs17728338; P=4.15 × 10⁻¹³), IL13 (rs1295685; P=1.65 × 10⁻⁷), IL23A (rs61937678; P=1.82 × 10⁻⁷) and TNFAIP3 (rs642627; P=5.90 × 10⁻⁷) regions. We also imputed variants for eight HLA genes and found that SNP rs114255771 yielded a more significant association than any HLA allele or amino-acid residue. Further analysis revealed that the HLA-C*06-B*57 haplotype tagged by this SNP had a significantly higher odds ratio than other HLA-C*06-bearing haplotypes. The results demonstrate allelic heterogeneity at IL12B and identify a high-risk MHC class I haplotype, consistent with the existence of multiple psoriasis effectors in the MHC.     

Salmonella enteritidis : The Kinetics of Blood Clearance of Isotopically labelled • by the Reticulo-Endothelial System in Mice

The phagocytosis of ⁵¹Cr or ¹³¹I-labelled suspensions of heat-killed Salmonella enteritidis by the R.E.S. has been studied in mice and the results compared with the kinetic laws which govern the clearance of stable colloid suspensions.

Clearance of bacteria followed an exponential function for the first few minutes, during which about 60 per cent were phagocytosed. Thereafter, the rate of clearance became progressively slower. The maximum extraction by the liver and spleen was calculated as only 48 per cent. Previous administration of heparin slowed the initial clearance of all doses of bacteria exceeding 5 × 10⁷ per 20 g. No inverse relationship between dose and rate of clearance could be shown in either heparinized or normal mice. The greatest proportion of bacteria (70–80 per cent) were taken up by the liver. Bacteria were phagocytosed in preference to carbon particles, but were taken up less readily than heat-denatured albumin (CA). Blood clearance was promoted greatly by previous injection of specific immune serum and slightly by normal guinea-pig serum.

Further investigations suggest that apparent slowing in clearance is due to the fact that not all members of a bacterial population are equally susceptible to phagocytosis.

     

Genetic control of the humoral immune response to rabbit erythrocyte isoantigens

Blood group Hg^A negative rabbits were injected with 2 × 10⁹ Hg^A positive erythrocytes from a donor rabbit. Assortative matings were set up between those rabbits which produced detectable anti-Hg^A (responders) and those which did not (non-responders). The progeny were injected with 2 × 10⁹ Hg^A positive erythrocytes 3 months after birth and their anti-Hg^A response measured. It was found that 20/24 (83 per cent) of the offspring of responder parents, but only 4/26 (15 per cent) of the offspring of non-responder parents, produced detectable anti-Hg^A. No difference was found between the ability of responders and non-responders to produce haemagglutinins to various doses of sheep erythrocytes. In contrast, non-responder rabbits rarely responded to non-Hg^A blood group isoantigens on the donor erythrocytes whereas rabbits which responded to Hg^A after injection of the donor erythrocytes often responded to non-Hg^A isoantigens. Typing the cells of non-responder rabbits with the sera from responder rabbits containing non-Hg^A antibodies showed that the non-responder cells were antigenically more like the donor cells than were the cells from responder rabbits. The ability to respond to Hg^A was not associated with any particular heavy or light chain immunoglobulin allotype specificities. It is considered that Hg^A has an important helper function in regard to the antibody response to non-Hg^A antigens but the latter probably also have a similar but less marked effect in relation to the Hg^A antibody response. The genetic control observed is thought to operate through T cell recognition and reaction with Hg^A and other blood group determinants.