Genetic analysis of theT-H-2 region in non-t Chromosomes

A general breeding protocol useful in the construction of congenic lines of mice disparate in the 15 cMT-H-2 region of chromosome 17 in non-t chromosomes is described. Two such congenic lines, B6.TC2/Rn and B6.TC3/Rn, were derived from the C57BL/6J and B6.C-H-2 ^d/By strains using this protocol. Both B6.TC2 and B6.TC3 dissociate the quantitative activity locus for glyoxalase I (Qglo-1) from theH-2 complex, and hence possess BALB/cBy DNA centromeric toH-2. However, neither new strain is able to map anyH-2-associated restriction fragment length polymorphism with anH-2 cDNA probe even though both strains are recombinant in the 2 cMQglo-1-H-2K interval.     

Genetic regulation of early survival and cyst number after peroral Toxoplasma gondii infection of A x B/B x A recombinant inbred and B10 congenic mice

Genetics of two traits, survival and brain cyst number after peroral Toxoplasma gondii infection, were studied by using recombinant inbred strains of mice derived from resistant A/J (A) and susceptible C57BL/6J (B) progenitors, F1 progeny of crosses between A/J and C57BL/6J mice, and congenic mice (B10 background). Analysis of strain distribution pattern of survival of A x B/B x A recombinant mice indicated that survival is regulated by a minimum of five genes. One of these genes appears to be linked to the H-2 complex and another is related to an as yet unmapped gene controlling resistance to Ectromelia virus. Associations of defined traits with resistance or susceptibility to Toxoplasma cyst formation were also analyzed. Cyst number is regulated by a locus on chromosome 17 within 0 to 4 centimorgans of the H-2 complex (p = 0.001). Mice with the H-2a haplotype are resistant and those with the H-2b haplotype are susceptible. This analysis also indicated that the Bcg locus on chromosome 1 may effect cyst number (map distance = 12 centimorgans, p = 0.05). Resistance to cyst formation is a dominant trait. To analyze relative roles of H-2 and Bcg loci on cyst numbers, C57BL10 (B10)-derived congenic strains of mice with known H-2 and Bcg type were studied. These studies indicated that the H-2 complex locus has the primary effect on cyst number.     

Genotypic influences on reproductive aging of inbred female mice: effects of H-2 and non-H-2 alleles

The H-2 (major histocompatibility) complex of mice influences a variety of physiologic parameters. This study describes the influences of H-2 polymorphisms and other genetic influences on age-related changes (5-20 mo) in estrous cycles and fecundity. We monitored estrous cycles of virgin or retired-breeder mice of congenic strains on the background of C57BL/10Sn (B10):B10.BR/Sg (B10.BR) and B10.RIII/Sn (B10.RIII). For another comparison, we examined the C57BL/6J (B6) strain, which has the same H-2 haplotype as the B10. Estrous cycles were categorized by length during 10 mo of observations. From 5 to 15 mo of age, B10 and B10.RIII mice displayed a preponderance of 5-day cycles, B10.BR mice displayed a preponderance of 4-day cycles, and B6 mice had diminishing numbers of 4-day cycles. Age-related acyclicity differed with strain, particularly among retired breeders; B6 mice had an earlier onset and more rapid increase of acyclicity with age than the B10 congenic mice. Litters/female, maternal age at last litter, and total pups/female differed with strain; B10.BR and B10.RIII were similar and both had greater values than B10 mice. In conclusion, reproductive senescence of female mice was influenced by genes at the H-2 locus and elsewhere.     

Structural aspects of a protein epitope and their role in the major histocompatibility complex control of T cell responsiveness.

We have previously shown that immunization of C57BL/10 (H-2b) mice with the tobacco mosaic virus protein (TMVP) or with its tryptic peptide number 8, representing residues 93-112 of TMVP, induces T cells which proliferate in vitro in response to TMVP and peptide 8. In contrast, immunization of congenic B10.BR (H-2k) mice with either TMVP or with peptide 8 induces T cells which respond in vitro to the homologous but not the heterologous antigen. The capacity to exhibit cross-reactivity between TMVP and peptide 8 on the T cell level has been shown to be under major histocompatibility complex (MHC)-linked genetic control. The lack of cross-reactivity has been attributed to the inability of the H-2k APC to present the appropriate epitope to T cells. In the present paper, we report results of a comparative analysis of the role of structural aspects of the epitope on the proliferative T cell responses from TMVP and peptide 8-immune C57BL/10 (H-2b) and B10.BR (H-2k) mice. Utilizing a panel of synthetic peptides representing portions of peptide 8 and a panel of peptide-protein conjugates, we have determined that peptide 8-immune T cells of the H-2k strain appear to recognize a single epitope within peptide 8, located at its N-terminus. In contrast, in the H-2b strain, both TMVP and peptide 8-immune T cells appear to recognize two overlapping epitopes within peptide 8; one located in the middle region and the other toward the N-terminus. Experiments with H-2b T cells revealed that random amino acids added to the carboxyl or amino-terminus of nonstimulatory peptides can confer activity to these peptides, demonstrating limited specificity of interaction between antigen and Iab. Results of experiments dealing with fixation of antigen-presenting cells suggest that TMVP requires processing in order to be recognized by peptide 8-immune H-2b proliferative T cells whereas peptide 8 does not. Taken together the results suggest that the T cell responsiveness to TMVP and peptide 8 exhibited by these two congenic strains H-2b and H-2k is not only controlled by the strains MHC but is also influenced by antigen processing. Antigen processing may eliminate a potential epitope for the primary induction and the secondary stimulation of B10.BR T cells.     

The Locus Encoding αa-Crystallin Is Closely Linked to H-2K on Mouse Chromosome 17

We have used a complementary DNA (cDNA) for mouse alpha A-crystallin to probe genomic DNA for restriction fragment length polymorphisms which could be used to map the alpha A-crystallin gene locus (Acry-1) in the mouse genome. Ten of 12 restriction endonucleases produced fragment polymorphism among various inbred strains of mice. A comprehensive strain survey conducted with six endonucleases resulted in the discovery of six allelic forms of Acry-1. Linkage analysis was conducted on DNA from three sets of recombinant inbred strains of mice and demonstrated close linkage of Acry-1 with the major histocompatibility complex (H-2) on chromosome 17. Analysis of congenic and recombinant congenic strains of mice confirmed the linkage of Acry-1 and H-2 and located the alpha A gene to the region between glyoxylase (Glo-1) and H-2K.     

Genetic control of acquired resistance to visceral leishmaniasis in mice

A series of H-2 and non-H-2 congenic resistant (CR) strains on a C57BL/10Sn background were infected with 10(7) amastigotes of Leishmania donovani. Non-H-2 congenic strains B10.LP-H-3b and B10.CE(30NX) and (B10.LP-H-3b x B10)F1 hybrids showed a very rapid decrease in liver-parasite burdens beyond day 21. Parasite counts for these strains at day 35 were significantly lower than for all other strains tested. The rapid decrease in parasite numbers, massive lymphocellular infiltration into the liver and strong delayed hypersensitivity reactions to parasite antigens in strains congenic for a portion of chromosome 2 indicated that acquired immunity to L. donovani was controlled by a dominant gene at or near the Ir-2 locus. In addition, B10.129(10M) mice, which differ from C57BL/10Sn at the H-11 locus, showed highly significant increases in parasite numbers at day 35. Other observations supporting the absence of acquired immunity in B10.129(10M) included negative delayed hypersensitivity tests to parasite antigens and the absence of lymphocellular infiltrate into the liver. Although the differences were not as pronounced, H-2 CR strains with H-2b, H-2a, and H-2k haplotypes also showed significantly greater decreases in parasite numbers by day 35 as compared to other H-2 CR strains.     

Immunodominance in the T cell response to multiple non-H-2 histocompatibility antigens. IV. Partial tissue distribution and mapping of immunodominant antigens

The immunization of C57BL/6 responder mice with spleen cells from H-2-matched BALB.B donors, which differ by multiple non-H-2 histocompatibility (H) antigens, results in the generation of cytotoxic T lymphocytes (CTL) that are specific for only a limited number of immunodominant antigens. Previous analysis of the genes encoding these dominant antigens has not mapped these genes to any of the non-H-2 H loci defined by congenic strains. It would have been expected that the histogenetic techniques employed for congenic strain selection would have preferentially identified the "strongest" H antigens. Therefore, we have investigated the possibility that immunodominant antigens do not belong to the class of non-H-2 H antigens encoded by genes mapping to H loci defined and mapped by congenic strains. The first experiments were aimed at identifying antigens that were expressed by independently derived inbred strains and were cross-reactive with the immunodominant cytotoxic T cell target (CTT-1) antigen of BALB.B. Strong cross-reaction with the C3H.SW (H-2b) strain was observed; the C3H gene encoding this antigen was mapped with BXH recombinant inbred strains. Contrary to the mapping of the CTT-1 gene to chromosome 1 in BALB.B, the C3H gene was shown to map to either chromosome 4 or chromosome 7. This result indicates that identical, or at least extensively cross-reactive, non-H-2 antigens may be encoded by genes mapping to independently segregating loci in different inbred strains. The tissue distribution of immunodominant antigens was approached by determining the reactivity of CTL specific for these antigens with either lymphoid-derived or fibroblast-derived targets. These CTL effectively lysed lymphoblast and lymphoid tumor targets but did not lyse an SV40-transformed fibroblast line that was shown to be efficiently lysed by CTL specific for non-H-2 H antigens defined by congenic strains. Therefore, it was concluded that immunodominant antigens detected by B6 anti-BALB.B CTL have a restricted tissue distribution in comparison to non-H-2 H antigens defined by congenic strains. The implications of these results for our understanding of the origin and heterogeneity of non-H-2 cell-surface antigen recognized by effector T cells are discussed.     

Genetic regulation of the immune response to hepatitis B surface antigen (HBsAg). V. T cell proliferative response and cellular interactions

We previously demonstrated that in vivo antibody production to HBsAg in the mouse is regulated by at least two immune response (Ir) genes mapping in the I-A (HBs-Ir-1) and I-C (HBs-Ir-2) subregions of the H-2 locus. To confirm that H-2-linked Ir genes regulate the immune response to HBsAg at the T cell level and to determine if the same Ir genes function in T cell activation as in B cell activation, the HBsAg-specific T cell responses of H-2 congenic and intra-H-2 recombinant strains were analyzed. HBsAg-specific T cell proliferation, IL 2 production, and the surface marker phenotype of the proliferating T cells were evaluated. Additionally, T cell-antigen-presenting cell (APC) interactions were examined with respect to genetic restriction and the role of Ia molecules in HBsAg presentation. The HBsAg-specific T cell proliferative responses of H-2 congenic and intra-H-2 recombinant strains generally paralleled in vivo anti-HBs production in terms of the Ir genes involved, the hierarchy of responses status among H-2 haplotypes, antigen specificity, and kinetics. However, the correlation was not absolute in that several strains capable of producing group-specific anti-HBs in vivo did not demonstrate a group-specific T cell proliferative response to HBsAg. The proliferative responses to subtype- and group-specific determinants of HBsAg were mediated by Thy-1+, Lyt-1+2- T cells, and a possible suppressive role for Lyt-1-2+ T cells was observed. In addition to T cell proliferation, HBsAg-specific T cell activation could be measured in terms of IL 2 production, because anti-HBs responder but not nonresponder HBs-Ag-primed T cells quantitatively produced Il 2 in vitro. Finally, the T cell proliferative response to HBsAg was APC dependent and genetically restricted in that responder but not nonresponder parental APC could reconstitute the T cell response of (responder X nonresponder)F1 mice, and Ia molecules encoded in both the I-A and I-E subregion are involved in HBsAg-presenting cell function.     

A new erythrocytic antigen of C57BL/10 (B10) mice

A new antigen, detectable on murine erythrocytes by hemagglutination assay with a (BALB/cCrl X SWR/J)F1 anti-B10.D2n/Sn alloantiserum, is described. Among the inbred and congenic mouse strains tested for reactivity with the antiserum, only the immunizing strain, B10.D2, and its congenic resistant partner, C57BL/10 (B10), reacted. Three other C57 strains, C57BL/6J, C57BL/6By, and C57L, were negative for the antigen. F1 hybrids between B10 and BALB/c, an antigen-negative strain, were positive for the antigen indicating that its expression is dominant. Typing of 39 (BALB/c X (BALB/c X B10)F1) and 62 [BALB/c X B10)F1 X BALB/c) backcross mice revealed that a single gene controls expression of the antigen. The gene is autosomal and not linked to H-2, Ly-4, or the c (albino) or b coat color genes.     

Studies ofH-2K b mutant mice

Three newH-2 ^b mutant strains, B6.C-H-2 ^bm9 , B6.C-H-2 ^bm10 and B6.C-H–2 ^bm11 , are described. The three mutant strains are of the gain and loss type as they reject skin grafts reciprocally with the parental C57BL/6Kh. The mutations, which arose independently, are all allelic at the same locus as 11 other mutant strains already described. By complementation and other studies the mutated gene has been shown to beH-2K ^b . The strains were typed directly and by absorption with antisera specific for H-2K^b and H-2D^b private and public specificities and for Ia^b specificities. Each strain typed differently with these sera. The strain B6.C-H-2 ^bm9 was found to be serologically identical with C57BL/6. The strains B6.C-H-2 ^bm10 and B6.C-H-2 ^bm11 were found to have alterations in the private H-2K^b specificity, H-2.33, and in the public specificity, H-2.5, but to a different extent. B6.C-H- 2^bm10 had a marked decrease in the amount of H-2.33 expressed on the splenic cell surface as compared to C57BL/6 and also has a marked decrease in the expression of H-2.5 on both spleen and red blood cells. In comparison, B6.C-H-2 ^bm11 has a decrease in the expression of H-2.33 but an increase in the expression of H-2.5 on both splenic and red blood cells. The other H-2^b specificities appeared to be unaltered as compared with C57BL/6.     

Influence of immunizing dose and presence or absence of adult worms on the development of resistance to Nematospiroides dubius challenge infections of mice

H-2 congenic strains expressing resistant (H-2q, H-2f) or susceptible (H-2k) haplotypes were compared for their ability to resist challenge infection with N. dubius following a 6- or 14-day ivermectin-abbreviated immunizing infection. B10.BR mice (H-2k) were considerably more resistant to infection when the priming interval was shortened from 14 to 6 days. B10.Q (H-2q) and B10.M (H-2f) mice resisted challenge regardless of which immunization regimen was used. The influence of parasite numbers on the response to challenge was studied by comparing infections in resistant DBA/1 (H-2q) and susceptible CBA/J (H-2k) mice that differ at both H-2 and non-H-2 genes. DBA/1 mice, immunized with 50 or 150 L3 of N. dubius for 14 days, resisted challenge, whereas mice receiving 300 worms did not. In contrast, CBA/J mice failed to resist challenge at all priming doses tested. When the immunizing infection was shortened from 14 to 6 days, DBA/1 mice resisted challenge regardless of priming dose and CBA/J mice resisted challenge only when the highest dose of 300 worms was used for priming. The data suggest that susceptible strains of mice may be preferentially immunosuppressed, particularly at low infective doses, and that suppression is associated with adult worms present in the lumen of the small intestine.     

Assignment of the Ly-6--Ril-1--Sis--H-30--Pol-5/Xmmv-72--Ins-3--Krt-1--Int-1--Gdc-1 region to mouse chromosome 15

Previous work has demonstrated linkage between Ly-6, H-30, and a locus, Ril-1, that affects susceptibility to radiation-induced leukemia. Results of preliminary linkage analyses suggested further that the cluster might be linked to Ly-11 on the proximal portion of mouse chromosome 2. Using molecular probes to examine somatic cell lines and recombinant inbred and congenic strains of mice, we have re-evaluated these linkage relationships. A cloned genomic DNA fragment derived from a retroviral site has been used to define a novel locus, Pol-5, that is tightly linked to both H-30 and Ril-1 as shown by analysis of the B6.C-H-30 ^c congenic mouse strain. Following the segregation of the Pol-5 mouse-specific DNA fragment in a series of somatic cell hybrids carrying various combinations of mouse chromosomes on a rat or Chinese hamster background mapped Pol-5 to mouse chromosome 15. During the course of these studies, restriction fragment length polymorphisms were defined associated with several loci, including Pol-5, Ly-6, Sis, Ins-3, Krt-1, Int-1, and Gdc-1. Three of these loci, Sis, Int-1, and Gdc-1, have been previously mapped to chromosome 15 by others using somatic cell hybrids or isoenzyme analyses. Following the inheritance of these eight loci in recombinant inbred strains of mice allowed the definition of a linkage group on the chromosome with the order Ly-6-Ril-1--Sis--H-30--Pol-5--Ins-3--Krt-1--Int-1--Gdc-1. Analyses of alleles inherited as passengers in B6.C-H-30 ^c, C3H.B-Ly-6 ^b, and C57BL/6By-Eh/+ congenic mouse strains and in situ hybridization experiments support the above gene order and indicate further that the cluster is located on distal chromosome 15, with Ly-6 and Sis near Eh.Abbreviations A agouti - Abl cellular homolog of the Abelson leukemia virus oncogene - Ada adenosine deaminase - Ak-1 adenylate kinase-1 - AXB A/J × C57BL/6J recombinant inbred strain - B2m beta-2 microglobulin - BXA C57BL/6J × A/J recombinant inbred strain - BXD C57BL/6J × DBA/2J recombinant inbred strain - BXH C57BL/6J × C3H/HeJ recombinant inbred strain - CXB BALB/cBy × C57BL/6By recombinant inbred strain - DNA deoxyribonucleic acid - Eh hairy ears - Fpgs folypolyglutamyl synthetase - FXI fractionated x-irradiation - Gdc-1 glycerol phosphate dehydrogenase-1 - Il2r IL-2 receptor - Ins-3 a novel insulinlike gene - Int-1 mammary tumor integration site-1 - Itp inosine triphosphatase - Krt-1 the locus designated here includes a cluster of at least three keratin genes - LTR long terminal repeat - Ly lymphocyte - Lv-6 lymphocyte antigen-6 - Ly-11 lymphocyte antigen-11 - MIH minor histocompatibility - Myc cellular homolog of the Abelson leukemia virus oncogene; pa, pallid; - Pol-5 locus encoding retroviral polymerase-5 - RFLP restriction fragment length polymorphism - RI recombinant inbred mouse strains - Ril-1 radiation-induced leukemia susceptibility-1 locus - SDP strain distribution pattern - Sis cellular homolog of the simian sarcoma virus oncogene - SFFV spleen focus-forming virus - Tpi-1 triosephosphate isomerase-1 - Ve velvet     

Allograft rejection-defined antigens of the B2m,H-3 region

In this report we delineate the production and histocompatibility characteristics of two new B2m, H-3 region congenic strains, B10.SM-a and B10.FS-a, and further characterize previously described strains. Strains C57BL/10 and B10-we are shown to be histocompatible by the exchange of skin grafts, as are strains B10.UW-we,un at, B10.UW we un a, B10.UW-we + a, B10.UW-+ + a and B10.LP-a. (The latter group will be called B10-H-3b when referred to collectively). C57BL/10, B10-H-3b, B10.C-a, B10.KR-a, B10-pa at, B10.SM-a, and B10.FS-a are shown to be histoincompatible by the rejection of exchanged skin grafts, and histoincompatibility between these strains has been localized to the B2m, H-3 region. The histoincompatibility between C57BL/10 and B10.FS-a is of particular significance because of the identity of these strains at the B2m, H-3 region loci B2m and H-3. Thus the B2m, H-3 region histoincompatibility herein described defines a new locus, which we have called H-42, the a allele being assigned to C57BL/10 and the b allele to B10.FS-a. By using cross-immunization techniques, four allograft rejection-defined reactivity patterns (ADR) have been defined that show concordant strain distribution patterns with the CTL-defined reactivity patterns described elsewhere. On the basis of data presented in this report indicating C57BL/10 and B10.FS-a to differ by a histocompatibility gene in the B2m, H-3 region, and data presented by Kurtz et al. elsewhere indicating C57BL/10 and B10.FS-a to possess the same alleles at the B2m and H-3 loci, the presence of at least three B2m, H-3 region loci-defining cell membrane antigens is established.     

Linkage of the Fv-2 gene to a newly reinserted ecotropic retrovirus in Fv-2 congenic mice

Restriction enzyme and Southern gel analyses were used to determine the number and location of endogenous ecotropic retroviruses in the germ line of several mouse strains congenic at the Fv-2 gene locus. A new endogenous ecotropic provirus was observed in the germ line of B6.S (Fv-2ss) mice, in addition to the resident provirus found in its congenic partner C57BL/6 (Fv-2rr). This new provirus was similar in structure to the C57BL provirus. The SIM strain of mice, the donors of the Fv-2s allele in B6.S mice, does not contain ecotropic proviruses, suggesting that the new provirus in the B6.S mouse strain arose by germ-line reintegration during the construction of this strain. Mendelian segregation analysis indicated that this new provirus was linked to the Fv-2 gene locus on chromosome 9. In three other Fv-2s congenic mouse strains--B10.C (47N), B6.C (H-7b), and C57BL/6J Trfa, Bgsd--no additional ecotropic endogenous viruses were detected, suggesting that the reinsertion event that occurred during the construction of B6.S is not essential for the acquisition of the Fv-2s phenotype in the C57BL genetic background. Although numerous reports of germ-line reinsertions of ecotropic virus in high-virus mouse strains have been received, the present results provide definitive evidence that similar germ-line amplifications of endogenous ecotropic virus can occur in a low-virus mouse strain.     

Genetically determined resistance to lethal murine cytomegalovirus infection is mediated by interferon-dependent and -independent restriction of virus replication.

Susceptibility of 4-week-old mice of different strains to lethal murine cytomegalovirus (MCMV) infection was studied. Strains homozygous for H-2k and C57BL strains were resistant to greater than or equal to 10(5.5) PFU. B10.BR mice congenic for C57BL background genes and H-2k were about 10-fold more resistant than either C3H/HeN or C57BL strains. BALB/c mice (H-2d) were susceptible (50% lethal dose, 10(5.05) PFU). This susceptibility was dominant over resistance associated with H-2k but not that associated with C57BL background genes. The dominant susceptibility trait segregated in backcross mice as if carried by a single gene. Virus replication in spleen cells in vivo correlated with susceptibility to lethal infection. A similar trend was found in tests of salivary glands. Replication of MCMV in vitro in cultures of adherent spleen cells and primary mouse embryo cells correlated with replication in vivo. Neutralization of interferon (IFN) in cultures of adherent spleen cells reversed H-2k-linked restriction of viral replication but had minor effects on cells of other strains. Natural killer cell responses to infection were often higher in more resistant strains, but B10.BR mice developed minimal natural killer cell responses. Specific antibody and cytotoxic T cell responses in B10.BR mice were similar or lower than in other strains. Thus, resistance to lethal MCMV infection was not immunologically mediated, was dependent on and reflected by the capacity of cells from a given mouse strain to support replication in vivo and in vitro, and was IFN dependent and recessive if linked to H-2k but IFN independent when associated with C57BL background genes.     

Genetic control of the induction of cytolytic T lymphocyte responses to AKR/Gross viral leukemias. II. Negative control by the Fv-1 locus in AKR mice of responder H-2b haplotype

To assess whether the presence of a responder H-2b haplotype would be sufficient to allow mice of nonresponder "high leukemic" phenotype to generate syngeneic anti-AKR/Gross virus cytolytic T lymphocytes (CTL), the AKR.H-2b strain was examined. Although capable of mounting vigorous apparent anti-minor histocompatibility-specific CTL responses, AKR.H-2b mice failed to produce anti-viral CTL after a variety of stimulation protocols. In contrast, the "doubly congenic" AKR.H-2b:Fv-1b strain was able to respond with substantial levels of H-2-restricted anti-AKR/Gross virus CTL activity. These results indicated that Fv-1n alleles could exert negative epistatic control over responder H-2b-encoded gene(s). Because the B6.Fv-1n congenic was also able to generate anti-viral CTL indistinguishable from the prototype B6 strain, however, it was apparent that other genes of AKR background were required for the Fv-1n-mediated inhibition in AKR.H-2b mice. The mechanism by which Fv-1 intereacted with other genes to override positive H-2b control appeared to be related to the expression of the CTL-defined, virus-associated antigens by normal AKR.H-2b cells. Thus, AKR.H-2b spleen cells but not thymus cells were able to stimulate the production of B6 anti-AKR/Gross virus CTL and were recognized as target cells by such anti-viral CTL. In contrast, both spleen cells and thymocytes from AKR.H-2b:Fv-1b mice were negative when tested as stimulator or target cells in these assays. In addition, AKR.H-2b but not AKR.H-2b:Fv-1b spleen cells were shown to display serologically defined gp70 determinants and the Gross cell surface antigen. Taking these data together, it appeared that the inhibition of anti-viral CTL responsiveness might be due to tolerance induced by the cell surface expression of virus-associated antigens by normal AKR.H-2b cells. Widespread display of viral antigens, in turn, may have been due to the permissive effects of Fv-1n on the spread of the early arising N-ecotropic, endogenous AKR leukemia virus controlled by other background genes. In this context, the implications of the multi-gene control of anti-AKR/Gross virus CTL production are discussed with respect to the induction of spontaneous leukemia in the high incidence AKR strain.     

H-Y antigen: No evidence for alleles in wild strains of mice

H-Y antigen(s) coded or controlled by the Y chromosome in a variety of wild mouse strains have been compared with those of the inbred laboratory strains C57BL/6 (B6) and C57BL/10 (B10). H-Y antigen(s) were detected by H-2-restricted cytotoxic T cells from B6 and B10 female mice primed in vivo and boosted in vitro with syngeneic male spleen cells: There was no difference in the degree of H-Y specific lysis of male cells from the C57BL strains and of F₁ hybrids or B6 congenic mice carrying the Y chromosome from the wild mouse strains examined. This result indicated that at the level of target cell specificity the H-Y antigen(s) from wild and laboratory strains were indistinguishable. H-Y antigen(s) were also found to be indistinguishable at the level of the in vitro induction of the anti H-Y cytotoxic response: F₁ female mice, primed in vivo and boosted in vitro with homologous F₁ male cells, all made H-Y-specific responses and where it could be examined, the target cell specificity of the anti-H-Y cytotoxic cells showed that B10 male cells as well as the homologous F₁ male cells (where the Y chromosome was derived from the wild strain) were good targets. Finally, possible differences in H-Y transplantation antigens between the wild strains and the B10 laboratory strain were examined by grafting F₁ male mice, the progeny of B10 females, and wild strain males with B10 male skin. These grafts were not rejected during an observation period of more than 9 months. Taken together, neither the cytotoxic data nor the skin graft data provide any evidence for allelism of H-Y even though the mouse strains examined were collected from widely disparate geographical locations.     

Specificity or affinity of cytotoxic T cells for self H-2K determinants apparently does not change between primary and secondary responses to ectromelia virus infection.

Lysis of virus-infected target cells by virus-specific cytotoxic T cells occurs where donors of T cells and targets share either H-2K or H-2D genes. The effect of four H-2K mutations on virus-induced antigens recognized by cytotoxic T cells from in vitro secondary response to infection was studied. B10.A(5R) cytotoxic T cells (which share the K end of H-2 with the mutant strains, except for the mutated gene(s)) efficiently killed virus-infected macrophage targets from mutant strains B6-H-2bg1 and B6-H-2bg2, were less effective against B6-H-2bh and did not appear to be cytotoxic for B6.C-H-2ba target cells. Conversely, B6-H-Ibg1 and B6-H-2bg2 cytotoxic T cells were more effective in killing virus-infected B10.A(5R) macrophages than B6-H-2bh and B6.C-H-2ba cytotoxic cells respectively. In addition, B6-H-2bg1 and B6-H-2bg2 cells appeared to be only slightly different from wild-type with respect to the interaction between virus-infected cells and T cells. The data obtained suggested that virus-induced antigenic patterns on infected B6.C-H-2ba (mutant) cells are more different antigenically from those on wild-type cells than are those on infected cells from the other mutants, B6-H-2bh, B6-H-2bg1 and B6-H-2bh2. This agrees with previous data using primary cytotoxic T cells and thus suggests that no detectable change in the affinity or specificity of cytotoxic T cell receptors occurs between primary and secondary responses to infection. These findings are also discussed in relation to the exclusion of T cells with receptors for H-2K determinants that are common to the mutants and wild-type, from the response to virus-infected self cells.     

Effects of H-2 complex and non-H-2 background on urethane-induced chromosomal aberrations in mice

The incidence of in vivo urethane-induced chromosomal aberrations was examined in H-2 congenic strains of mice with B10 and A backgrounds. Chromosome analysis of bone-marrow cells could divide 7 lines of A.H-2 congenic strains into 2 groups: one with a higher frequency of chromosomal aberrations such as in A/Wy (haplotype H-2a), A/J (H-2a), A.AL (H-2al) and A.TL (H-2tl), and the other consisting of A.TH (H-2t2), A.CA (H-2f), A.BY (H-2b) and A.SW (H-2s). The same tendency was also observed in the spleen cells. Among B10.H-2 congenic mice, B10.A (H-2a), B10.BR (H-2k), B10.A(3R) (H-2i3), B10.A(5R) (H-2i5) and B10.S(9R) (H-2t4) exhibited significantly higher rates of induced chromosomal aberrations than those in B10 (H-2b), B10.S (H-2s), B10.A(2R) (H-2h2), B10.A(4R) (H-2h4) and B10.S(7R) (H-2t2). To determine the effect on non-H-2 genetic backgrounds on urethane-induced chromosomal aberrations, 4 pairs of strains which have the same H-2 haplotypes, such as in B10 vs. A.BY (H-2b), B10.A vs. A/Wy (H-2a), B10.S vs. A.SW (H-2s), and B10.S(7R) vs. A.TH (H-2t2), were compared. The strains with a B10 background exhibited significantly higher frequencies of deletions and lower frequencies of exchanges than the strains with an A background. These data suggested that at least two genes are involved in the regulation of urethane-induced chromosomal aberrations in mice, one of which is mapped between the S and D regions in the H-2 complex, and another not belonging to H-2.     

Genetic regulation of the antibody response to H-2Db alloantigens in mice. IV. Antigens that activate helper T cells for IgG, coded for by the non-H-2 genome

When B10.A(5R) mice are immunized with congenic C57BL/10 cells only 2-ME-sensitive antibodies (IgM type) are found directed against H-2Db. To obtain 2-ME-resistant antibodies (IgG type) 5R mice must be immunized with noncongenic cells (e.g., A.BY); in this case non-H-2 cell surface antigens will activate helper T cells to induce anti-Db IgG antibody production by B cells. An attempt was made to define helper antigens that activate helper T cells. Neither N-2 antigens of seven H-2Db recombinant strains nor a limited set of non-H-2 cell surface antigens were able to serve as helper antigens. By using individual backcross mice as antigen, one helper antigen was found on the background of strain A under the conditions used, whereas other backgrounds may carry more than one antigen. The helper antigen is dominantly expressed in F1 mice and has to be presented on the same cell as H-2Db to induce the switch from IgM to IgG.