BALB Background Research Articles

The specificity of the antibody response to internal antigens ofAscaris: heterogeneity in infected humans, and MHC (H-2) control of the repertoire in mice

Children from an area of Africa endemic for the large roundworm of humans, Ascaris lumbricoides, were found to vary considerably in the specificity of their serum IgG response to the internal antigens of the parasite. This was particularly noticeable for responses to a 14-kD protein (ABA-1) of the parasite that has previously been shown to be the subject of a strong IgE antibody response in infected animals. The possibility that this heterogeneity in immune repertoire has a genetic basis was explored in inbred mice infected with Ascaris suum. This showed that no strain responded to all the potential antigens, that the recognition profiles of strains bearing independent haplotypes were unique, and only H-2-identical strains had responses of similar specificities. Major histocompatability complex (MHC) restriction was confirmed using H-2-congenic animals on BALB and B10 backgrounds, which responded according to their H-2 haplotype. It is likely, therefore, that it is the MHC which controls the repertoire to Ascaris antigens in infected people. If this is so, then there will be implications for immunopathology associated with ascariasis, and possibly also for resistance and susceptibility to infection.

Spontaneous Atherothrombosis and Medial Degradation in Apoe −/− , Npc1 −/− Mice

The formation of an occluding thrombus on a ruptured or eroded atherosclerotic plaque is the hallmark event leading to acute coronary syndromes, myocardial infarction, and sudden death in humans. However, other species are highly resistant to plaque complications, and the specific processes predisposing to plaque destabilization and thrombosis are poorly understood. Mice carrying a null mutation of a gene regulating intracellular cholesterol transport (the Niemann-Pick C1 [Npc1] gene) were crossed with apolipoprotein E (Apoe) knockout mice to examine the effect of Npc1 on atherosclerotic lesion formation. Double-mutant mice showed greater lesion area compared with Apoe-/- littermates. Remarkably, the double mutants also developed large, protruding thrombi associated with the plaques and prominent medial degradation with inflammatory cell infiltration into the adventitia. Genetic studies suggested that the BALB background was permissive for plaque complications compared with C57BL/6J, and a BALB susceptibility locus was mapped by linkage analysis to chromosome 6. Examination of clotting parameters in double-knockout mice revealed that native clotting times were shortened and thrombin-antithrombin complex and soluble CD40 ligand levels were elevated compared with wild-type controls. In addition, cathepsin K was induced in Npc1-/- macrophages, and cathepsin K immunostaining and elastase activity were increased in proximal aortas of double-mutant mice compared with controls. A defect in intracellular cholesterol trafficking caused by the Npc1 null mutation predisposes to increased lesion formation, atherothrombosis, and medial degradation. Plaque complications may require a procoagulant state and an increased protease activity, leading to plaque destabilization.

The development of effector T cell subsets in murine Leishmania major infection.

Leishmania major infection has proven an exceptional model for CD4+ subset development in inbred mice. Most strains contain infection coincident with the appearance of T helper 1 (Th1) cells that produce gamma-interferon (IFN-gamma) required for macrophage activation. In contrast, mice on the BALB background are unable to control infection due to the development of Th2 cells that produce counter-regulatory cytokines, particularly interleukin 4 (IL-4), capable of abrogating the effects of IFN-gamma. Selective gene disruption studies in mice have illustrated critical components of the host response to L. major. Mice deficient in beta 2 microglobulin, which have no major histocompatibility complex (MHC) class I or CD8+ T cells, control infection as well as wild-type mice, whereas mice deficient in MHC class II (and CD4+ T cells) suffer fatal infection. Mice with disruption of the gene coding IFN-gamma are also incapable of containing infection, reflecting absolute requirements for this cytokine. A number of interventions have been demonstrated to abrogate Th2 cell development in BALB mice, enabling these mice to control infection. Each of these--IL-12, anti-IL-4, anti-IL-2, anti-CD4 and CTLA4-Ig--has in common the capacity to make IL-4 rate limiting at the time of CD4+ cell priming.

Non-MHC genes determine the development of lupus nephritis in H-2 identical mouse strains.

Susceptibility to systemic lupus erythematosus (SLE) and, in particular, lupus nephritis is strongly influenced by genetic factors. Previous studies have shown that MHC-related antigens influence the development of SLE. In the current study, we set out to investigate how non-MHC genes influence the pathogenesis of glomerulonephritis in chronic graft-versus-host disease (GVHD) in mice, a model for lupus nephritis. For the induction of GVHD we used parent-to-F1 hybrid mouse strain combinations. DBA/2, BALB/c, BALB.D2 and C57B1/10.D2 (BL10.D2) donor lymphocytes carrying an H-2d haplotype were injected into H-2b/d F1 hybrids of BL10 mice, which differed only at non-MHC loci. Within these hybrid strains the development of immune complex glomerulonephritis was investigated by monitoring the occurrence of autoantibodies in the circulation, deposition of immunoglobulins in the glomeruli, development of albuminuria, and glomerulosclerosis. In diseased DBA/2 mice albuminuria developed 6 weeks after induction of the disease. Mice with a BALB background developed a lupus-like syndrome characterized by albuminuria starting 8 weeks after induction of the GVHD. During the development of the GVHD, polyclonal B cell activation occurred in both the DBA/2 and BALB/c strains, resulting in the formation of autoantibodies. Only the strain combination using DBA/2 mice developed anti-GBM antibodies. In DBA/2 and BALB strain combinations immune complexes were detected in a granular pattern along the glomerular capillary walls. In the DBA/2 recipients a linear pattern of immunoglobulin depositions preceded the granular phase. This study demonstrates that: (i) non-MHC genes govern the pathogenesis of immune complex nephritis in this model by influencing the autoantibody profile; and (ii) the presence of anti-GBM antibodies in the early stages of the disease is a conditio sine qua non for the development of full-blown glomerulonephritis and glomerulosclerosis in this model.

Acceptance of Third‐Party Cardiac but not Skin Allografts Induced by Neonatal Exposure to Semi‐Allogeneic Lymphohematopoietic Cells

Neonatal tolerance is exclusively donor-specific when assessed by skin allograft survival and in vitro alloreactivity assays. In contrast, we reported previously that acceptance of primarily vascularized cardiac allografts was not donor-specific in C3H/He (C3H, H-2(k)) mice treated as neonates with BALB/c-derived (BALB, H-2(d)) lymphohematopoietic cells, but included third-party C57BL/10 (B10, H-2(b)) allografts. The present study examined whether this unusual pattern is limited to heart grafts in this strain combination, and defined the relative importance of the donor cell H-2(d) haplotype for third-party cardiac allograft acceptance. C3H neonates were injected with (C3HxBALB)F1 bone marrow and spleen cells. Tolerance was assessed at age 8-10 weeks by transplantation of heart or skin allografts from several donor strains, and by in vitro assays of proliferation and cytotoxicity. Additionally, cells from H-2(d) and H-2(b)-expressing strains on BALB or non-BALB minor histocompatibility (miH) antigen backgrounds were tested as tolerizing inocula. Prolonged survival of cardiac grafts from all donor strains was observed in neonatally treated mice, whereas skin grafting and in vitro assays demonstrated donor-specific hyporesponsiveness. Both H-2(d) haplotype and non-H-2 miH background of graft donor and tolerizing cell donor were important to third-party cardiac allograft acceptance. These results suggest that the functional alteration in alloreactivity induced by neonatal alloantigen exposure depends partly on method of assessment.

A locus affecting immunoglobulin isotype selection (Igis1) maps to the MHC region in C57BL, BALB/c and NOD mice.

We have previously shown that H2b mice with B10 or BALB genetic backgrounds have higher basal levels of IgG2a than H2k and H2d congenic strains and, hence, have low IgG1/IgG2a ratios, which is consistent with a T1 cytokine milieu. The phenotypic marker of the high IgG2a levels, denoted immunoglobulin isotype-1 (Igis1) was provisionally mapped telomeric of IEbeta using MHC recombinant mice. In addition, data from B10.A(2R), B10.A(1R) and B10.A(18R) mice indicated that Igis1 may lie in a 27 kb region between G7b (Sm-X5) and G7c. In the present study we confirm that Igis1 is in the H2 region using BALB and B10 congenic F2 mice. H2bb F2 mice had higher IgG2a levels than the H2dd parental strains. H2bd F1 and F2 mice on the B10 background produced IgG2a levels comparable with the H2bb parental strain, indicating that the b allele was dominant. In contrast, the H2bd F1 and F2 mice on the BALB background produced IgG2a levels between those of the H2bb and H2dd parental strains, indicating codominance of the b and d alleles. This suggests that a background gene influences regulation of IgG2a levels by Igis1. Non-obese diabetic (NOD) mice (KdIAg7IEnu11Db), which can develop type 1 diabetes, had higher levels of IgG2a than NOD-H2d congenic mice. Thus, Igis1 affects isotype selection in the presence of non-MHC diabetes genes. As type 1 diabetes is associated with T1 responses, Igis1 may affect susceptibility to this condition.

CD3- bone marrow cells augment the generation of cytotoxic T lymphocytes showing a preference for the X-chromosome linked gene product of stimulator cells.

Responder cells, composed of both a limited number of nylon wool-passed lymph node (NW-LN) cells and an excess number of CD3+ cell-depleted bone marrow (CD3- BM) cells from the same strain of mice, were stimulated with allogeneic spleen cells in vitro. The CD3- BM cells augmented the generation of allogeneic major histocompatibility complex (MHC) class I specific cytotoxic T lymphocytes (CTL) from NW-LN cells. C3H/He (H-2k, C3H background) responder cells were stimulated with either B10.D2 (H-2d, B10 background) or BALB/c (H-2d, BALB background) spleen cells. In the former stimulation, the CTL induced lysed B10.D2 target cells more efficiently than the BALB/c cells. Furthermore, these CTL lysed more (B10.D2 x BALB/c) F1 male target cells than (BALB/c x B10.D2) F1 male. In the latter stimulation, the CTL lysed more BALB/c than B10.D2 cells, and more (BALB/c) x B10.D2) F1 male than (B10.D2 x BALB/c) F1 male. The reciprocal mixed lymphocyte cultures (MLC) were carried out, in which BALB/c responder cells were stimulated with either C3H/He or B10.BR (H-2k, B10 background) spleen cells. In the former stimulation, the CTL induced lysed more C3H/He or (C3H/He x B10.BR) F1 male target cells than B10.BR or (B10.BR x C3H/He) F1 male, and in the latter, the reciprocal results were obtained. These results suggested that the CTL induced had a preference for the X-chromosome linked gene products (Xlgp), besides the specificity for the allogeneic MHC class I, of the mice used as stimulator.

Systemic T Helper 2 Cell Activation Is Not Sufficient for Antigen-Induced Eosinophil Recruitment into the Airways

Background: Airway eosinophilic inflammation is a characteristic feature of asthma. We have previously shown that antigen-induced eosinophil recruitment into the airways of sensitized BALB/c mice is mediated by CD4+ T cells and IL-5. However, the basis for the eosinophil recruitment into the airway are still largely unknown. Methods: To determine the regulatory mechanisms that control the magnitude of antigen-induced eosinophilic inflammation in the airways, we analyzed antigen-induced eosinophil and T cell infiltration into the trachea in several strains of mice, including BALB/c (H-2^d), BALB/b (H-2^b), C57BL/6 (H-2^b), C57BL/10 (H-2^b), and B10.D2 (H-2^d) mice. In addition, cytokine production from antigen-stimulated splenocytes and the titer of antigen-specific IgE antibody in serum were assessed. Results: Antigen-induced eosinophil recruitment into the trachea in BALB/c mice was more than 20 times as abundant as that in C57BL/6 mice, the latter of which was also mediated by CD4+ T cells. In contrast, systemic Th2 responses, which were evaluated by the titers of antigen-specific IgE antibody in serum and antigen-induced IL-4 and IL-5 production from splenocytes, were similarly observed in BALB/c mice and C57BL/6 mice. In addition, the antigen-induced eosinophil recruitment into the trachea was high in BALB/b mice, like BALB/c mice, but low in B10.D2 mice. Conclusions: Systemic Th2 responses are not sufficient for causing antigen-induced eosinophil recruitment into the airways and an undefined determinant(s) that exists in the BALB background mice rather than the H-2 haplotype is vital for the regulation of antigen-induced eosinophil recruitment into the airways.

BALB/c Mice Produce Blister-Causing Antibodies Upon Immunization with a Recombinant Human Desmoglein 3

Pemphigus vulgaris (PV) is an Ab-mediated autoimmune blistering disease of mucotaneous surfaces. Over 95% of the patients with PV express DR4 or DRw6, and the disease is characterized by the presence of autoantibodies directed against desmoglein 3 (Dsg 3), a protein expressed on keratinocytes. An appropriate animal model is required to understand immunoregulation and to address the role of immunogenetic components in the production of pathogenic Abs that are characteristic of PV. Therefore, we turned to the development of a mouse model. Four strains of female mice (BALB/c, DBA/1, SJL/J, and HRS/J) were screened for their ability to produce pathogenic anti-Dsg 3 Abs. We demonstrated that only BALB/c mice immunized with a full-length Dsg 3 can produce pathogenic Abs capable of causing acantholysis of human foreskin in culture and blistering in neonatal mice. This observation suggested that either H-2d or the BALB background contains the immunogenetic makeup necessary for the production of pathogenic anti-Dsg 3 Abs. No correlation was noted between a given isotype and the pathogenic potential of autoantibodies from different strains of mice. Similarly, the pattern of reactivity of Abs with a panel of 46 synthetic peptides that span the entire Dsg 3 failed to reveal any association between binding specificity and the pathogenic potential, and suggested that pathogenic Abs might recognize conformational epitopes. Moreover, our studies showed that the epitopes recognized by pathogenic Abs are contained within the extracellular Dsg 3.

Non-MHC-linked Th2 cell development induced by soluble protein administration predicts susceptibility to Leishmania major infection.

Continuous administration of soluble protein Ag followed by immunization with the same Ag in adjuvant results in the selective development of Ag-specific CD4+ Th2 cells in both normal and beta2-microglobulin-deficient BALB/c mice. In addition to chronic administration by mini-osmotic pump, single bolus i.p., but not i.v., injection of protein Ag induces Th2 cell expansion. Strong Th2 cell priming depends on a non-MHC-linked genetic polymorphism. It is observed in all congenic strains on BALB background tested, BALB/c, BALB/b, and BALB/k, but not in MHC-matched strains on disparate genetic background, B10.D2, C57BL/6, and C3H. DBA/2 mice appear to have an intermediate phenotype, as shown by their weaker capacity to mount Th2 responses as compared with BALB/c mice after soluble Ag administered by either mini-osmotic pumps or single bolus i.p. Conversely, induction of Th1 cell unresponsiveness by soluble protein is observed in any mouse strain tested, following any mode of Ag administration. These data demonstrate that non-MHC-linked genetic polymorphism controls the priming of Th2 but not the inhibition of Th1 cells induced by administration of soluble protein. The pattern of Th2 responses in these different strains is predictive of disease outcome following Leishmania major infection and supports the hypothesis that systemic Ag presentation in the absence of strong inflammatory signals may represent an important stimulus leading to selective Th2 cell development in susceptible mouse strains.

Extrathymic Development of Self-Reactive γδ T Cells in Athymic BALB/cnu/nuMice

In the present report, we demonstrated that extrathymic γδ T cells proliferated in the mixed culture of lymph node cells of BALB/cnu/numice and irradiated syngeneic spleen cells (syngeneic MLR). Reverse transcription–polymerase chain reaction (RT-PCR) analyses revealed that Vδ5 and Vδ6 were dominantly expressed by the γδ T cells from the syngeneic MLR. Furthermore, the syngeneic MLR may expand Vδ5+T cells with BALB invariant delta (BID) sequence which is specifically detected in BALB background mice because Vδ5 RT-PCR products from syngeneic MLR were digested with anAluI restriction enzyme which cut the Dδ2–Jδ1 junction of the BID sequence but not those of most non-BID Vδ5 sequences. Interestingly, anti-mycobacterial and mammalian heat shock protein (Hsp) 60 mAb ML30 suppressed the generation of Vδ5 with anAluI site in syngeneic MLR. These results suggest that extrathymically derived Vδ5+and Vδ6+γδ T cells recognize BALB/c self antigens and that the Hsp60 or an Hsp60-related molecule may be involved in the anti-self response of Vδ5+BID+γδ T cells.

Limited role of CD28-mediated signals in T helper subset differentiation.

The role of CD28-mediated signals in T helper cell maturation is not fully understood. We tested the requirement for costimulation through CD28 in several systems of CD4+, T cell differentiation. In vivo priming of mice with genetic disruption of CD28 (CD28-/-) yielded normal levels of antigen-specific interferon gamma production but markedly diminished levels of interleukin 4 (IL-4) after in vitro restimulation. In response to the pathogenic microbe, Leishman a major, C57BL6 CD28-/- mice were fully capable of controlling infection and exhibited a normal T helper 1 response. BALB/c CD28-/- mice unexpectedly exhibited normal susceptibility to L. major. BALB/c CD28-/- mice developed high levels of IL-4 mRNA and protein induction in the draining lymph nodes. In addition, susceptibility of BALB/c CD28-/- mice was reversed by neutralization of IL-4 in vivo. We also activated transgenic CD28-bearing T cells from the BALB and C57BL background in vitro in the presence of CTLA4Ig. BALB cells had greater IL-4 producing capacity than C57BL cells in the absence of costimulation. Diverse factors including costimulatory signals, genetic polymorphism, and the nature of the immunogen all influence T helper phenotype commitment, but these results provide evidence that CD28 is not an absolute requirement for generating either Th1 or Th2 responses.

Genetic control of susceptibility toTaenia crassicepscysticercosis

We previously reported that genes within the major histocompatibility complex influence the intensity of Taenia crassiceps murine cysticercosis. This genetic control, readily apparent in mice of BALB background, was further studied in H-2 congenic and recombinant B10 mice as well as in BALB/c substrains differing in expression of Qa-2 antigens. Similarly low parasite numbers were found in all B10-derived strains infected, regardless of H-2 haplotype, indicating that the effect of H-2 genes in controlling susceptibility is overridden in mice of B10 background. BALB/c substrains differed significantly in susceptibility. BALB/cAnN was highly susceptible, whereas BALB/cJ, in contrast, was highly resistant and BALB/cByJ showed intermediate susceptibility. Susceptibility or resistance in BALB/c substrains may be associated to differences known to distinguish them, such as serum testosterone levels and Qa-2 protein expression. In bidirectional F1 hybrids of C57BL/6J and BALB/cAnN resistance to cysticercosis was inherited as a dominant autosomal trait. In F1 hybrids of BALB/cJ with BALB/cAnN, BALB/cByJ and BALB.K resistance was also inherited as a dominant trait. However, in (BALB/cAnN x BALB/cByJ)F1 and (BALB/cAnN x BALB.K)F1 hybrids, dominant susceptibility to cysticercosis was observed.

Impact of MHC class I gene on resistance to murine AIDS.

Development of murine AIDS in mice following infection with LP-BM5 murine leukaemia virus (MuLV) is highly strain dependent, with strain differences determined by genes within and outside H-2. Among H-2 genes, the Dd gene is the most closely associated with resistance to LP-BM5 MuLV infection. However, the Dd-mediated resistance is highly influenced by outside H-2 genes, i.e. A lineage strains are more resistant than mice strains of B6/B10 lineage. In this study, the mice having BALB background were analysed and, similarly to A lineage mice, only Dd gene products were found to be required to provide resistance to LP-BM5 MuLV infection. Furthermore, BALB/c Kh mice bearing both Dd and Ld genes clearly showed obviously higher resistance than BALB/c-H-2dm2 mice solely having the Dd gene. In addition, in the long-term observation of the effect of the Dd gene on B6/B10 background mice, D8 mice having the Dd gene as a transgene and expressing a high level Dd gene product showed higher resistance than naturally recombinant B10.A(18R) mice. These results suggest that the MAIDS resistance associated with the D end loci is dependent on the level of expression of an MHC class I gene.

Epitope-specific antibody response against glycoprotein E of pseudorabies virus.

In this study we investigated the epitope-specific antibody response against glycoprotein E (gE) of pseudorabies virus. Epitope-specific antibody responses were investigated by enzyme-linked immunoperoxidase monolayer assays. In a vaccinated crossbred pig population, most pigs responded to antigenic domain E and to a lesser degree to antigenic domains C and D. Only few pigs responded to antigenic domains F, A, and B. Using vaccinated pigs, we investigated the influence of two different pseudorabies virus strains and the genetic background of the host on the epitope-specific antibody response. More pigs infected with the virulent NIA-3 strain had a detectable antibody response against antigenic domains C, F and A than did pigs infected with the mildly virulent Sterksel strain (P < or = 0.05; Fisher's exact test). No differences in the epitope-specific antibody responses of two genetically different pig breeding lines were observed (P > or = 0.1; Fisher's exact test). In both breeding lines the incidence of the epitope-specific antibody response was comparable to that in the crossbred pig population. In addition, we studied the epitope-specific antibody responses were strikingly different and indicated that genetic background influenced the epitope-specific antibody response. Of the serum samples of mice with C57BL and a BALB background, 40 and 17% respectively, were positive in the one of the epitope-specific immunoassays. In contrast to pigs, mice responded predominantly to antigenic domain D and to a lesser degree to antigenic domains E and B. Only few mice had a detectable antibody response against antigenic domains C and A, and none had a detectable antibody response against antigenic domain F.

Influence of genes within the MHC on mortality and brain cyst development in mice infected with Toxoplasma gondii: kinetics of immune regulation in BALB H‐2 congenic mice

Previous work has shown that genes within the major histocompatibility complex (MHC) of the mouse influence resistance and susceptibility to Toxoplasma gondii infection. Initial studies presented here using B10 H-2 congenic and recombinant haplotype mice inoculated via the oral route with the low virulence Beverley strain of T. gondii confirm the D region localization of MHC-linked control of brain cyst number. All B10 mice were, however, exquisitely sensitive to minor changes in virulence of the parasite inoculum resulting in high mortality during the early acute phase of infection. Further experiments examining mortality and brain cyst number in BALB MHC congenic mice inoculated via different routes indicated that the BALB background would provide a more favourable genetic environment in which to analyse kinetics of MHC controlled immune regulation following infection via the natural (oral) route. In studies comparing d and k haplotype mice a dramatic inverse relationship between splenic CD4:CD8 T cell ratios and brain cyst number was observed, particularly in the strain (BALB/K; H-2k) most susceptible to high brain cyst numbers and subsequent toxoplasmic encephalitis. Of particular interest was the observation that splenomegaly and the relative increase in the splenic CD8 T cell population preceded and accompanied the very dramatic and rapid increase in brain cyst formation. The results suggest that the too rapid development of a potent anti-parasite response in the viscera may drive the parasite to encyst in the brain.

Cytolytic activity of murine CD4+ T cell clones correlates with IFN-gamma production in mouse strains having a BALB/c background.

Abstract CD4+ murine T cell clones were derived from various strains of mice, and their pattern of lymphokine secretion and cytolytic activity was compared. Limiting dilution cultures were established with lymph node cells from mice sensitized with OVA. Alloreactive CD4+ T cell clones also were derived in limiting dilution cultures prepared with naive BALB/c-H-2dm2 lymph node cells stimulated with irradiated BALB/c splenocytes. A total of 24 days elapsed between establishment of cultures and analysis of lymphokine production and cytolytic activity. Cytolytic capacity was assessed by using target cells that had been pulsed with Ag or coated with anti-CD3 mAb. We observed that: 1) the frequency of OVA-reactive T cells from various mouse strains was approximately the same; 2) both Th1 and Th2 cells as well as cells not encompassed within these categories could be lytic if derived from DBA/2, B10.D2, B10.A, C57BL/10, or C57BL/6 mice; and 3) the vast majority of CD4+ cloned T cells derived from BALB/c, BALB/c-H-2dm2, BALB.B, or BALB.K that did not produce IFN-gamma (including Th2 cells) did not exhibit cytolytic activity, whereas most clones derived from these strains that produced IFN-gamma were cytolytic. These observations indicate that both Th1 and Th2 cells from several mouse strains express cytolytic activity. Such cytolytic activity was not restricted to clones maintained in long term cultures. However, genes outside the MHC appeared to regulate the cytolytic activity of T cells. In particular, CD4+ T cell clones which did not produce IFN-gamma were not cytolytic when they were derived from BALB/c mice and mutant or MHC congenic inbred mice having a BALB background. Cytolytic activity of CD4+ T cells, in addition to the pattern of lymphokine production, may be important in graft rejection and in immune responses to infectious diseases.

Host strain, H-2 genotype and immunocompetence do not affect the survival or development of Onchocerca lienalis infective larvae implanted within micropore chambers into mice or rats.

The survival, growth and development of Onchocerca lienalis 3rd-stage (L3) larvae implanted into mice within micropore chambers has been studied with a view to developing a vaccination model for studies of protective immunity in onchocerciasis. The influence of host genetics on worm recoveries and development (growth and moulting rate) was analysed in a panel of inbred mice (CBA, BALB/c, DBA/2, SJL, 129J, C57BL/10 (B10), C3H/He and NIH), together with mice of BALB and B10 backgrounds with different major histocompatibility complex (H-2) genes (BALB/c, BALB.K, BALB.B and B10, B10.D2/n, B10.BR, B10.S). Parasite recoveries and development were similar in all mouse genotypes tested. They were unaffected by procedures designed to block or modulate phagocytic cell function with carbon or carrageenan, or to suppress inflammation by treatment with hydrocortisone acetate. A comparison of chambers sealed with membranes designed to admit (5.0 microns pore size) or exclude (0.2 microns pore size) host cells demonstrated no effect on the percentage recovery of living larvae, although dead larvae were more frequently retrieved when cells were excluded. Recoveries and rates of development of larvae implanted into immunodeficient scid mice and athymic Hooded rats were similar to those recorded in immunocompetent controls. We conclude that host genetic factors and immunocompetence are not significant determinants of survival, growth or development of O. lienalis larvae implanted within micropore chambers into naive mice. Despite its limitations, the use of this system merits further investigation as an approach to the study of protective immunity against developing larvae in onchocerciasis.

Studies on a murine model of congenital toxoplasmosis: vertical disease transmission only occurs in BALB/c mice infected for the first time during pregnancy.

The incidence of congenital toxoplasmosis was determined by an ELISA in the litters of BALB/c mice which had been infected 8 weeks before mating, on day 12 of pregnancy, or on both these occasions. Of those mice given the infection for the first time on day 12 of pregnancy, 5 out of 6 gave birth to infected litters with approximately 50% of the individuals in each litter being infected. BALB/c mice which had been infected 8 weeks before mating did not give birth to infected litters, even if they were reinfected on day 12 of pregnancy. Following infection BALB/c mice were found to harbour significantly fewer tissue cysts than the congenic H-2 derivative BALB/K strain. However, chronically infected BALB/K mice also failed to produce infected litters, indicating that tissue cyst burden in the dam did not influence congenital infection at least on the BALB background. This study demonstrates that BALB/c dams chronically infected with Toxoplasma gondii, have immunity capable of protecting their embryos from congenital infection, even if the dams are reinfected during pregnancy. Our results demonstrate that the BALB/c mouse can be used as a model of human or ovine congenital T. gondii infection suitable for testing putative vaccines.

Genetic control of the immune response in mice to Leishmania mexicana surface protease.

Congenic mouse strains were tested in the lymphocyte proliferation assay for their response to the purified surface protease of Leishmania mexicana (gp63). The data obtained allow us to distinguish three different patterns of response, influenced both by H-2 (class II) and non-H-2 genes. Mice of the C57BL/10 (B10) background carrying H-2 haplotypes b,q, and r were found to be high responders; those carrying H-2 haplotypes d, j, v, and z were low responders; and those with H-2a, H-2f, H-2k, H-2p, and H-2u haplotypes were intermediate responders. Studies with H-2 recombinant strains indicated that the high responsiveness on the B10 background was determined by the Ab allele and the low responsiveness influenced by the Ad allele. Other genes besides H-2 appear to have a role in the immune response as shown by the fact that some strains with BALB, DBA, or C3H background differed in their pattern of responsiveness from B10 background strains carrying the corresponding H-2 haplotypes. By using recombinant protein, the influence of the leishmanial surface lipophosphoglycan that might co-purify with gp63, on the MHC restriction of the response to gp63 was excluded. The immune response to gp63 did not correlate with susceptibility of mouse strains to cutaneous infection with L. mexicana promastigotes.