Cellular and metabolic requirements for induction of macrophage procoagulant activity by murine hepatitis virus strain 3 in vitro.

The cellular basis for the variation in induction of monocyte procoagulant activity (PCA) by murine hepatitis virus strain 3 (MHV-3) was examined using a set of recombinant inbred strains of mice derived from the resistant (A/J) and susceptible C57B1/6J (B) progenitors. Induction of PCA by MHV-3 required live virus and host protein and RNA synthesis. Absolute restriction for induction of PCA was observed at the level of the macrophage. Peritoneal macrophages from resistant parental A/J and RI strains (AXB5) could not be induced to express PCA when stimulated by MHV-3 alone or in the presence of lymphocytes from susceptible and H-2 compatible RI mice (AXB3) although they did respond to endotoxin (LPS). In contrast, macrophages from both susceptible (AXB3) and semisusceptible (AXB1) RI strains of mice expressed a similar increase in PCA after stimulation with MHV-3 in the absence of lymphocytes. The levels of PCA expressed by macrophages in the presence of Thy-1.2+ lymphocytes correlated with susceptibility to disease. Thy-1.2+ lymphocytes from susceptible RI AXB3 mice could induce levels of PCA in macrophages from semisusceptible RI AXB1 mice equivalent to that seen in cultures of macrophages and lymphocytes from susceptible mice. Further subfractionation of Thy-1.2+ cells demonstrated that L3T4+ cells instructed macrophages to produce PCA. Thy-1.2+ cells from MHV-3 immunized resistant AXB5 mice, but not from non-immunized mice, were able to suppress induction of PCA. This suppressor cell activity could be detected 4 days after immunization, reaching maximal activity at day 7 with significant suppression even at 28 days. The PCA was shown to have direct prothrombin cleaving activity (prothrombinase) by ELISA and immunofluorescence staining using the mAb 3D4.3. These results demonstrate that induction of a unique PCA (prothrombinase) is restricted at the level of the macrophage and define a regulatory role for T lymphocytes in its induction.     

The immune response to mouse hepatitis virus: expression of monocyte procoagulant activity and plasminogen activator during infection in vivo

After infection with 10(3) plaque-forming units of mouse hepatitis virus strain 3 (MHV-3) in vivo, peripheral blood mononuclear cells and splenic cells expressed procoagulant activity (PCA) in a pattern directly correlating with susceptibility to disease. Mononuclear cells from BALB/cJ mice, a strain which is fully susceptible to MHV-3, expressed a greater than 500-fold increase in PCA. PCA was first detected within 12 hr of infection; prior to histologic evidence of disease and viral replication, it reached maximal levels 48 hr post-infection (p.i.) and persisted until the death of the animals 5 to 7 days p.i. Mononuclear cells from C3HeB/FeJ mice expressed a significant but lesser titer of PCA, with elevated PCA persisting throughout the chronically infected state until death of the animals 4 to 6 mo p.i. Basal levels of PCA were detected in mononuclear cells from fully resistant A/J mice despite the presence of large amounts of virus in livers, spleens, and sera from these animals. When mononuclear cells expressing high PCA were subfractionated, monocytes were found to be the cellular source of greater than 96% of the PCA activity. Increased plasminogen activator activity was found in monocytes from resistant A/J mice at the time when PCA was markedly elevated in BALB/cJ and C3HeB/FeJ mice. This activity persisted for 5 to 7 days p.i., but was undetectable 10 days p.i. at a time when the mice had cleared the virus from their blood streams. These observations suggest that monocyte PCA may be important in the pathogenesis of MHV-3 disease, whereas the production of monocyte plasminogen activators may contribute to resistance of A/J mice to MHV-3-induced liver disease.     

Genetic resistance to mouse hepatitis virus correlates with absence of virus-binding activity on target tissues.

The molecular mechanism of genetic resistance of inbred mouse strains to mouse hepatitis virus, a murine coronavirus, was studied by comparing virus binding to plasma membranes of intestinal epithelium or liver from susceptible BALB/c and resistant SJL/J mice with a new solid-phase assay for virus-binding activity. Virus bound to isolated membranes from susceptible mice, but not to membranes from resistant mice. F1 progeny of SJL/J X BALB/c mice had an intermediate level of virus-binding activity on their enterocyte and hepatocyte membranes. This correlated well with previous studies showing that susceptibility to mouse hepatitis virus strain A59 is controlled by a single autosomal dominant gene (M. S. Smith, R. E. Click, and P. G. W. Plagemann, J. Immunol. 133:428-432). Because virus binding was not prevented by treating membranes with sodium dodecyl sulfate, the virus-binding molecule could be identified by a virus overlay protein blot assay. Virus bound to a single broad band of Mr 100,000 to 110,000 in membranes from hepatocytes or enterocytes of susceptible BALB/c and semisusceptible C3H mice, but no virus-binding band was detected in comparable preparations of resistant SJL/J mouse membranes. Therefore, SJL/J mice may be resistant to mouse hepatitis virus A59 infection because they lack a specific virus receptor which is present on the plasma membranes of target cells from genetically susceptible BALB/c and semisusceptible C3H mice.     

Role of interferon in the pathogenesis of viral diseases of mice as demonstrated by the use of anti-interferon serum. V. Protective role in mouse hepatitis virus type 3 infection of susceptible and resistant strains of mice

Potent sheep anti-mouse interferon globulin has been used to determine the role of virus-induced interferon in mouse hepatitis virus type 3-infected susceptible (C57BL/6), semiresistant (C3H/He), and resistant (A/J) strains of mice. Injection of anti-interferon globulin accelerated the onset of death in C57BL/6 mice, induced almost 100% mortality in C3H/He mice that usually do not die of acute disease, and caused death in 4- and 6-week-old A/J mice, but not in older mice. We conclude that interferon is an important host defense factor in the initial response of different strains of mice to MHV-3 infection. Other factors, however, such as the capacity of macrophages to restrict viral multiplication probably underlie the genetically determined susceptibility or resistance of mice to MHV-3 infection.     

Association between nitric oxide synthesis and vaccination-acquired resistance to murine hepatitis virus by spf mice

Murine hepatitis virus strain 3 (MHV-3) produces a strain-dependent pattern of disease, with A/J and BALB/c mice being considered models of resistance and susceptibility, respectively. A role for nitric oxide in controlling infection remains debatable; thus, we monitored nitric oxide levels in blood and liver of immunized and nonimmunized spf mice during infection by electron paramagnetic resonance. In parallel, liver histology, virus titers, and plasma alanine aminotransferase (ALT) activity were monitored. Nitric oxide synthesis was barely detectable in BALB/c mice, which showed a progressive increase in virus titers and ALT activity. These animals died with a shorter survival time than A/J mice. The latter displayed a less severe infection and presented detectable levels of nitric oxide as nitrosyl complexes in blood and liver at 72 hpi. Immunized mice from both strains became resistant to MHV-3 and showed comparable levels of nitrosyl complexes in blood and liver at an early time (24 hpi). Thereafter, nitric oxide levels decreased but remained detectable in blood up to 96 hpi. Immunized mice were capable of clearing the virus and clearance was inhibited by administration of a nitric oxide synthase inhibitor. Overall, the results support a role for nitric oxide in controlling MHV-3 infection.     

Susceptibility to a mouse acquired immunodeficiency syndrome is influenced by theH-2

The development of a mouse acquired immunodeficiency syndrome (MAIDS) induced following LP-BM5 MuLV infection depends on host genetic factors. Susceptible mice, such as C57BL/6J mice, develop a profound impairment of lymphoproliferative response to mitogens and hyperplasia of lymphoid organs and succumb to infection within 6 months. These changes do not occur in resistant mice, such as A/J mice. Resistance to MAIDS is a dominant trait since (C57BL/6JxA/J)F₁ hybrid mice did not develop any immune dysfunctions following infection. Genetic regulation of the trait of resistance/susceptibility to MAIDS was determined in AXB/BXA recombinant inbred (RI) mouse strains (derived from resistant A/J and susceptible C57BL/6J progenitors). Two different criteria were used to determine their resistance or susceptibility to developing MAIDS: the gross pathologic evaluation of lymphoid organs at 13–15 weeks of infection, and survival. RI mouse strains segregated into two non-overlapping groups. The first group did not develop any significant pathology, and these mouse strains were considered as resistant to MAIDS. The second group showed the virus-induced pathological changes as well as an immunological dysfunction as seen in C57BL/6J progenitor mice, and these strains were thus considered as susceptible to MAIDS. This bimodal strain distribution pattern of resistance/susceptibility to MAIDS among the RI strains suggests that this phenotype is controlled by a single gene. Linkage analysis with other allelic markers showed a strong association between resistance/susceptibility to MAIDS and theH-2 complex. Possession of theH-2 ^b haplotype derived from C57BL/6J mice was associated with susceptibility to MAIDS, while theH-2 ^a haplotype conferred resistance to the disease. This finding was confirmed by demonstrating thatH-2 ^a congenics on the susceptible C57BL/10 background were as resistant to MAIDS as A/J mice which donated theH-2 ^a locus. Gene(s) within theH-2 complex thus represent the major regulatory mechanism of resistance/susceptibility to MAIDS.     

Genetically determined resistance to mouse hepatitis virus 3 is expressed in hematopoietic donor cells in radiation chimeras

Differences in mouse hepatitis virus 3 (MHV3) sensitivity among mouse strains are mainly determined by H-2-related and -nonrelated genetic factors. Reciprocal chimerism was therefore established between two H-2a compatible pairs of strains that differ widely in their susceptibility to MHV3: a) A/J and B10.A, respectively resistant and highly susceptible; b) A/J and A/Sn, respectively resistant and semisusceptible. Chimeric mice were challenged with 100 LD50 of MHV3, 30 or 90 days after X-irradiation (900 R) and bone marrow reconstitution. Results showed that sensitivity of recipients was similar either to that of the recipient strain or to that of the donor strain when chimeric mice were tested 30 or 90 days, respectively, after reconstitution. In addition, no paralysis occurred in surviving animals. These data indicate, therefore, that resistance or susceptibility to MHV3 is expressed intrinsically in some population(s) of hematopoietic-derived cells, which is radioresistant and has a life span of more than 30 days and less than 90 days. Additional experiments showed that X-irradiated A/J recipients reconstituted with A/J bone-marrow cells were protected against MHV3 challenge with spleen cells, with a mixture of spleen cell populations or of adherent spleen cells and thymocytes originating from A/J donors. Transfer of protection to recipients by using similar cell populations provided by semisusceptible A/Sn donors required the administration of five times more cells. Results suggest that two complementary mechanisms are required to confer resistance to MHV3: a) a gene(s) for resistance that may operate at the level of macrophages, and b) cells capable of mounting an efficient immune response. The reduced efficiency of A/Sn spleen cells suggests that semisusceptibility to MHV3 may be related to partial quantitative or functional immune defect.     

Genetic Analysis of Audiogenic Seizure Susceptibility in C57bl/6j x Dba/2j Recombinant Inbred Strains of Mice

The inheritance of susceptibility to audiogenic seizures (ASs) was studied in the C57BL/6J (B6) and DBA/2J (D2) progenitor strains, their reciprocal F₁ hybrids, backcross generations and in 21 B6 x D2 recombinant inbred (RI) strains of mice at 21 days of age. All of the D2 mice tested experienced ASs, whereas none of the B6 mice responded to the sound. Although 23% of the F₁ mice experienced wild running, they were generally as resistant to ASs as their B6 parents. Mice of the F₁ x B6 backcross generation were also resistant to ASs. In the F₁ x D2 backcross generation, however, a significant preponderance (72%) of AS-susceptible mice was found. No significant association was observed between any of the four coat-color phenotypes that were segregating in this generation and susceptibility to ASs. A continuous distribution of mean seizure severity scores and several new audiogenic response phenotypes, distinctly different from the phenotypes of either progenitor strain, were found among the 21 RI strains. These and the results from the F₁ x D2 backcross generation suggest that the difference in AS susceptibility between 21-day-old B6 and D2 mice cannot be under the control of a single locus. In addition, no association was found between AS susceptibility and the chromosome 4 markers Lyb-2, Mup-1 and b among the 21 RI strains. An association was observed, however, between AS susceptibility and the Ah locus. Several of the RI strains that were AS resistant at 21 days of age became AS susceptible as adults. One RI strain was susceptible to ASs at both young and adult ages. The B6, D2 and F₁ mice were completely resistant to ASs at adult ages. Genetic differences were found among the RI strains for the incidence, onset, duration, and type of severity of ASs. A remarkable amount of phenotypic variability in the audiogenic response, which can be attributed only to the influence of environmental factors, occurred within several of the RI strains. A multiple-factor mode of inheritance involving a physiological threshold can account for our observations.     

Chromosomal locations and gonadal dependence of genes that mediate resistance to ectromelia (mousepox) virus-induced mortality.

Four genetic loci were tested for linkage with loci that control genetic resistance to lethal ectromelia virus infection in mice. Three of the loci were selected because of concordance with genotypes assigned to recombinant inbred (RI) strains of mice derived from resistant C57BL/6 and susceptible DBA/2 (BXD) mice on the basis of their responses to challenge infection. Thirty-six of 167 male (C57BL/6 x DBA/2)F1 x DBA/2 backcross (BC) mice died (22%), of which 27 (75%) were homozygous for DBA/2 alleles at Hc and H-2D. Twenty-eight percent of sham-castrated and 6% of sham-ovariectomized BC mice were susceptible to lethal mousepox, whereas 50% of gonadectomized mice were susceptible. There was no linkage evident between Hc or H-2D and loci that controlled resistance to lethal ectromelia virus infection in 44 castrated BC mice. Mortality among female mice of BXD RI strains with susceptible or intermediate male phenotypes was strongly correlated (r = 0.834) with male mortality. Gonadectomized C57BL/6 mice were as resistant as intact mice to lethal ectromelia virus infection. These results indicate that two gonad-dependent genes on chromosomes 2 and 17 and one gonad-independent gene control resistance to mousepox virus infection, that males and females share gonad-dependent genes, and that the gonad-independent gene is fully protective.     

Genetics of resistance to the African trypanosomes. VI. Heredity of resistance and variable surface glycoprotein-specific immune responses

The question of genetic linkage of parasite-specific immune responses to resistance to infection in experimental African trypanosomiasis was addressed. For this purpose, major histocompatibility complex-compatible resistant and susceptible inbred mouse strains and their F1 hybrid, F2 hybrid, and backcross offspring were infected with Trypanosoma brucei rhodesiense LouTat 1. Immunologic control of the first peak of parasitemia and survival times were the parameters measured. As we have reported previously (R. F. Levine and J. M. Mansfield, J. Immunol. 133:1564, 1984), B10.BR/SgSnJ mice are relatively resistant and controlled the growth of the infecting variant antigenic type (VAT) by mounting an antibody response to exposed epitopes of the variable surface glycoprotein (VSG). Fluctuating parasitemias resulting from sequential growth of different variable antigenic types occurred subsequently, and these mice died with a median survival time of 48 days. C3HeB/FeJ mice, relatively susceptible, did not control the infecting VAT and did not exhibit VSG-specific antibodies. These mice died with a median survival time of 22 days. The (B10.BR X C3H)F1 hybrids derived from crosses between resistant and susceptible mice all exhibited VSG-specific antibody responses and controlled the infecting VAT population. However, the median survival time of the F1 hybrids (24 days) was not significantly different from the survival time of the susceptible C3H parent. These findings demonstrate for the first time that antibody-mediated control of parasitemia is inherited as a dominant trait; that overall resistance, as measured by survival time, is inherited as a recessive trait (e.g., susceptibility is dominant); and that the two events segregate independently of one another. Further analyses of the inheritance of immunity and resistance (survival time) were made in which the F2 hybrid and backcross studies revealed that there are multiple genes controlling the VSG-specific antibody response as well as determining susceptibility. An extension of the present studies to a similar but non-major histocompatibility complex-mouse model system of resistance and susceptibility (C57BL/6J and C3H/HeJ mice, F1 hybrids, and 11 recombinant inbred B X H strains derived from them) was made in order to link the strain distribution patterns of known genetic markers with control of VSG-specific antibody responses or with control of susceptibility. Results of this study showed that resistance varied independently of the ability to control parasitemia with VSG-specific B cell responses.(ABSTRACT TRUNCATED AT 400 WORDS)     

Genetic and phenotypic analysis of seizure susceptibility in PL/J mice

Epilepsy is one of the most common but genetically complex neurological disorders in humans. Identifying animal models that recapitulate human epilepsies is important for pharmacological studies of anticonvulsants, dissection of molecular and biochemical pathogenesis of epilepsy, and discovery of epilepsy susceptibility genes. We discovered that the PL/J inbred mouse strain is susceptible to handling- and rhythmic tossing–induced seizure. The tonic–clonic and generalized seizures observed after induction were accompanied by abnormal EEGs, similar to seizures observed in EL and SWXL-4 mice. PL/J mice also had an extremely low threshold to electroconvulsive seizures compared to other strains and showed variable sensitivity to pentylenetetrazole-induced seizures. Gross neurostructural abnormalities were not found in PL/J mice. Crosses with the seizure-resistant C57BL/6 J strain revealed semidominant inheritance of the rhythmic tossing seizure trait with low penetrance. F2 progeny indicated that the genetic inheritance of seizure susceptibility in PL/J is non-Mendelian. We crossed DBA/2 J mice, which are resistant to rhythmic tossing seizure but susceptible to audiogenic seizures, to PL/J. We found that seizure penetrance in (DBA/2 J × PL/J)F1 mice was similar to the penetrance in (C57BL/6 J × PL/J)F1 mice but the severity and frequency of seizure were higher in (DBA/2 J × PL/J)F1 mice. The PL/J strain serves as an interesting new model for studying the genetics, neurobiology, and pharmacology of epilepsy.     

Trypanosoma cruzi: Correlation of resistance and susceptibility in infected inbred mice with the in vivo primary antibody response to sheep red blood cells

Nonspecific immune responses during the course of murine Trypanosoma cruzi infection were examined in mouse strains genetically resistant or susceptible to the Brazil strain of T. cruzi. Spleen cells from infected susceptible (C3H) or resistant [C57 B1/10 and FI (C3H × C57)]mice at various points during the course of infection exhibited a reduced response to concanavalin A and lipopolysaccharide in vitro. Since this reduced response occurred in both susceptible and resistant mice, it was not predictive of resistance or susceptibility in vivo. We next examined the kinetics of in vivo primary antibody response to sheep red blood cells (SRBC) in infected C3H and C57 mice. C3H mice exhibited inhibition of the direct plaque-forming cell assay (d-PFC) which persisted until death. In contrast C57 mice exhibited no inhibition of the response at Day 5 and subsequently a markedly augmented response was observed. Other strains of mice were similarly investigated: all the susceptible mice examined (A/J, BALB/c) showed inhibition or depression of the primary antibody response and resistant mice [B10Br, C57B1/10, SJL, F1 (C3H × C57)]demonstrated either no inhibition or considerable augmentation of this response. CS7 mice resistant to the Brazil strain were susceptible to the Tulahuén strain. The mice in this latter group exhibited a markedly significant inhibition of the in vivo primary antibody response to SRBC. Culture forms of the Brazil strain protected C3H mice from a virulent challenge. This immunization resulted in a markedly augmented antibody response. The data reported herein are consistent with the notion that inhibition of the primary antibody response to SRBC correlates with susceptibility whereas no inhibition or, indeed, augmentation of the response correlates with natural as well as acquired resistance.     

SJL/J Mice Are Highly Susceptible to Infection by Mouse Adenovirus Type 1

Mouse adenovirus type 1 (MAV-1) targets endothelial and monocyte/macrophage cells throughout the mouse. Depending on the strain of mouse and dose or strain of virus, infected mice may survive, become persistently infected, or die. We surveyed inbred mouse strains and found that for the majority tested the 50% lethal doses (LD(50)s) were >10(4.4) PFU. However, SJL/J mice were highly susceptible to MAV-1, with a mean LD(50) of 10(-0.32) PFU. Infected C3H/HeJ (resistant) and SJL/J (susceptible) mice showed only modest differences in histopathology. Susceptible mice had significantly higher viral loads in the brain and spleen at 8 days postinfection than resistant mice. Infection of primary macrophages or mouse embryo fibroblasts from SJL/J and C3H/HeJ mice gave equivalent yields of virus, suggesting that a receptor difference between strains is not responsible for the susceptibility difference. When C3H/HeJ mice were subjected to sublethal doses of gamma irradiation, they became susceptible to MAV-1, with an LD(50) like that of SJL/J mice. Antiviral immunoglobulin G (IgG) levels were measured in susceptible and resistant mice infected by an early region 1A null mutant virus that is less virulent that wild-type virus. The antiviral IgG levels were high and similar in the two strains of mice. Taken together, these results suggest that immune response differences may in part account for differences in susceptibility to MAV-1 infection.     

Comparative teratogenicity of phenytoin among several inbred strains of mice

Inbred strains of mice differ in their response to the embryopathic effects of phenytoin (PHT). A/J animals, the most susceptible strain, were mated to C57BL/6J mice, the most resistant strain. The susceptibility of the F1 hybrid offspring was determined by the susceptibility of the mother. B6AF1 animals were as resistant as C57BL/6J parental mice, and AB6F1 hybrids were as susceptible as A/J mice. This was especially evident when orofacial anomalies were tallied. (B6A)F2 hybrid offspring were as resistant as their C57BL/6J grandparents.     

Neonatal susceptibility to MHV3 infection in mice. I. Transfer of resistance.

Up to 3 weeks of age, mice of the resistant A/J strain are fully susceptible to mouse hepatitis virus type 3 infection (MHV3). Immune deficiency, however, resulting from neonatal thymectomy or long term ALS administration led A/J animals to remain susceptible when tested at adult age. Whole spleen cells transferred from normal adult A/J donor mice protected suckling syngeneic recipients from i.p. infection with MHV3. Such a protective capacity of spleen cells was abolished after treatment with anti-theta serum and complement. Spleen cell separation by means of adherence to plastic also showed that neither the nonadherent nor the adherent populations injected separately were able to confer resistance to young mice challenged with the virus. Protection was not achieved with peritoneal cells originating from adult syngeneic animals. Transfer of resistance to MHV3 was obtained, however, when peritoneal cells were associated with adherent spleen cells. This study indicated that two types of mature cells, at least, were required for transferring MHV3 resistance into newborn mice of the A/J strain: T lymphocytes and an adherent spleen cell population.     

Comparison of lung virus titers in susceptible and resistant inbred mouse strains against Sendai virus infection

Susceptibility of inbred mouse strains to Sendai virus (Mol strain) infection was studied. Although some mouse strains showed age differences in susceptibility between 3-to 4-week-old and 7-to 8-week-old mice, such age differences in susceptibility were not observed in susceptible DBA/2N and resistant BALB/cA mice. In 7-to 8-week-old mice, remarkable strain differences were observed in mortality and intensity of the lung lesions, but not in lung virus titers and serum antibody, between resistant BALB/cA and susceptible DBA/2N mice.     

Genetic control of resistance to murine malaria

Strain variation in the level of resistance to malaria was investigated in inbred mice after infection with Plasmodium chabaudi. Following intraperitoneal infection with the typing dose of parasitized erythrocytes, mice of 11 inbred strains could be separated using survival time as the criterium into resistant and susceptible groups. Genetic analysis of F₁ hybrid and backcross progeny derived from one of the most resistant (B10.A) and from the most susceptible (A/J) strains as parents suggested that host resistance in this strain combination was genetically controlled by a dominant, non-H-2-linked, autosomal gene or closely linked genes. Analysis of the mechanisms of resistance to P chabaudi showed (1) phenotypic expression of the resistance gene was apparent within 6 days of infection as a significant difference between resistant and susceptible mice in the level of parasitemia; (2) the level of host NK cell activity was not related to the level of host resistance to malaria; (3) compared with susceptible A/J mice, resistant B1O.A hosts had an augmented erythropoietic response during the course of malaria as well as during phenylhydrazine-induced anemia and (4) treatment with BCG or P acnes resulted in an equal degree of protection, measured by parasitemia and survival, in both resistant and susceptible mice.     

The p47 GTPases Iigp2 and Irgb10 regulate innate immunity and inflammation to murine Chlamydia psittaci infection

C57BL/6J mice were 10(5)-fold more resistant to Chlamydia psittaci infection than DBA/2J mice by LD(100) determinations. Linkage analysis using BXD recombinant inbred strains revealed a single effector locus at a 1.5-Mbp region on chromosome 11 encoding a cluster of three p47 GTPases (Irgb10, Igtp, and Iigp2). Western blots of infected tissue showed that Irgb10 was elevated in resistant mice and one of the two possible Iigp2 protein isoforms was preferentially expressed in susceptible mice. The BXD39 strain, susceptible at Irgb10 and resistant at Iigp2, had an intermediate phenotype implicating the nonredundant role of these p47 GTPases. C57BL/6J and DBA/2J exhibited a difference in IFN-gamma-dependent chlamydial control, which was reversible by Iigp2 small interfering RNA knockdown. Microarrays of infected peritoneal lavage revealed >10-fold up-regulation of neutrophil-recruiting chemokines in susceptible mice and >100-fold increase in macrophage differentiation genes in resistant mice, indicating that the susceptibility pattern involves the stimulation of different inflammatory cell-recruiting pathways. Massive neutrophil recruitment was seen in susceptible mice by histology and flow cytometry, and neutrophil chemokine receptor (CXCR2) knockout mice on a susceptible background survived a lethal challenge, confirming that neutrophil recruitment was required for susceptibility. Congenic Igtp knockout mice also susceptible at Irgb10 and Iigp2 on a resistant background recruited neutrophils and succumbed to infection. We conclude that Irgb10 and Iigp2 act together to confer differential susceptibility against murine chlamydial infection. Data indicate that these p47 GTPases have cell-autonomous effects that result in vastly different inflammatory stimulations, leading to either recovery or death.     

The C5-sufficient A/J congenic mouse strain. Inflammatory response and resistance to Listeria monocytogenes

A/J mouse strain poorly responds to an inflammatory stimulus and is highly susceptible to Listeria monocytogenes (Lm) infection. This defect in the phagocyte inflammatory response caused by the C5 component of C deficiency was shown, by linkage analysis, to be the major reason for the extreme susceptibility of A/J mice to Lm infection. The importance of this genetic defect in C5 in relation to the poor macrophage inflammatory response and to the susceptibility to Lm infection was evaluated by developing a C5-sufficient congenic A/J mouse strain. This A/J.C5 mouse strain was studied for its inflammatory response and for its susceptibility to Lm infection. C5-sufficient congenic A/J.C5 mice showed a slight improvement (2X) in their level of macrophage inflammatory response; however, they did not mount an as strong response as the Listeria-resistant C57BL/6J mice which donated the C5 allele. When infected with Lm, A/J.C5 mice were found to be as resistant as C57BL/6J mice. These results suggest that the presence of C5 on an A/J background partially improves the deficient macrophage inflammatory response of that strain. This increase is sufficient to render the A/J.C5 mouse strain highly resistant to Listeria infection. A/J.C5 mouse strain represents a new tool for the study of the importance of C5 in resistance to infection and in the regulation of the macrophage inflammatory response.