Both genetic background and environmental factors modify the phenotypic expression of H-2 associated genes participating in the polygenic control of antibody responsiveness to Salmonella antigens.

The genetic control of responsiveness to flagellar (f) and somatic (s) antigens of Salmonellae was studied in high (H) and low (L) lines of mice selected for the character 'antibody response to sheep erythrocytes'. The minimal immunogenic dose was, for the two antigens, lower in H than in L mice and the dominance of the responder phenotype was then greater in F1 hybrid females than in males. Genes associated with H-2 locus intervene in the responses to each antigen. Their expression was found to vary according to the conditions of immunization and to the sex. The quantifiable H-2 effect was measured in interline hybrids, i.e. on an heterogeneous genetic background equivalent to that of F2. In the case of the flagellar (f) antigen, the H-2 locus was responsible in secondary response for about 50% of the interline difference in the two sexes. In the primary response, the H-2 effect was only observed in females. It was smaller (25% of the interline difference) and independent of the antigen dose. In contrast, with somatic (s) antigen the H-2 locus did not intervene in the control of secondary response. The H-2 effect in the primary response was again only found in females. Unexpectedly, the allele linked to the H-2 phenotype of L mice had a more favourable effect on hybrid responsiveness than that linked to the phenotype of H mice.     

Genetic parameters of the polygenic regulation of antibody responsiveness to flagellar and somatic antigens of salmonellae

Selective breedings of mice were carried out for quantitative antibody responsiveness to flagellar Ag., f (Selection III) or somatic Ag., s (Selection IV) of two non cross-reacting Salmonellae (Salm. tm., Salm. or.) alternated for immunization of consecutive generations. At the selection limit, these selections produced homozygous high (H) and low (L) responder lines for the character investigated: peak agglutinin response to optimal secondary immunization. The responsiveness to both f and s Ags. is submitted to polygenic regulation. The heritability (h2) realized during the selective breeding was 0.37 +/- 0.07 for the response to fAg. and 0.40 +/- 0.1 for the response to s Ag. The respective part of genetic and environmental variance in F2 hybrids was 64% and 36% in selection III and 61% and 39% in selection IV. In the two selections, the dominance variance is negligible (less than 1%), therefore the genetic variance is essentially additive. The additive variance calculated as the heritable fraction of the F2 hybrid variance is somewhat lower, the reason for this difference is discussed. The quantitative antibody response to f Ag. in selection III is controlled by about seven independent loci. The antibody response to s Ag. in selection IV is controlled by about four independent loci. A possible association of relevant genes with the H-2 locus was investigated. In selection III, no significant participation if H-2 linked genes, in the regulation of responses to f and s Ags. of Salm. tm and Salm. or. could be demonstrated. In selection IV a partial contribution of H-2 linked genes was observed concerning responsiveness to both f and s Ags. of Salm. tm. but not Salm. or. Ags. The H-2 effect accounts for 25% of the total interline difference.     

Role of immune responsiveness and DNA repair capacity genes in ageing

The genetic factors that determine immune responsiveness and DNA repair capacity are reviewed as major elements influencing the life span. Within this framework two sets of new data obtained in mice and humans are reported and discussed. As to the first set, the role of immune response genes was investigated in Biozzi mice genetically selected for high (H) or low (L) antibody response. After 15-20 generations of assortative mating, H and L mice exhibited almost complete intraline homozygosity and interline polymorphism including distinct H-2 haplotypes, such as q in H and s in L mice. In order to analyze the impact of quantitative trait loci (QTL) on the antibody response as well as on the DNA repair capacity in cells of the immune system independently of the selected H-2 haplotype, congenic Hq and Hs as well as Lq and Ls mice were produced and analysed. Both the antibody response and DNA repair capacity were found to be independent of the H-2 haplotype and determined by QTL. As to the second set of data, DNA repair was also studied in irradiated peripheral blood mononuclear cells (PBMC) from ageing humans. The levels of ku 70, ku 80, DNA-PKcs, phosphorylated ku 80 as well as the DNA-binding activity of the ku70/ku 80 heterodimer were determined in the cytoplasmic and nuclear extracts obtained, before and after irradiation, from young and elderly subjects. The results of this study suggest that the decreased DNA repair capacity in PBMC from elderly subjects may be related to impaired migration of the phosphorylated ku 80 from the cytoplasm to the nucleus. This finding helps to elucidate questions related to the impairment of DNA repair during ageing.     

Correlation between genetic regulation of antibody responsiveness and protective immunity induced by Plasmodium berghei vaccination.

High (H) and low (L) antibody responder lines of mice were produced by two independent bidirectional selective breedings for quantitative antibody responsiveness to heterologous erythrocytes (selection I and selection II). In both selections the antibody response to P. berghei antigens was 8- to 10-fold higher in H than in L lines. The character "high response" presents an incomplete dominance o- 18% in selection I and 67% in selection II. In selection II the variance analysis indicates that at least three independent loci intervene in the regulation of responsiveness to P. berghei antigens. The innate resistance and the protective efficacy of vaccination against P. berghei infection induced by parasitized erythrocytes was measured in H and L lines and in the interline hybrids F1, BcH, and BcL of selections I and II. No very significant difference was observed in the innate resistance to P. berghei infection between H and L mice of both selections. Vaccination induced a very efficient protection in the two H lines (94 and 95% survival), whereas only a weak protection was induced in the two L lines (16 and 31% survival); the degree of protection is intermediate in interline hybrids F1, BcH, and BcL. In both selections a good linear correlation was demonstrated between the level of vaccination-induced antibody and the degree of resistance measured as percentage of survival. The present results indicate that the vaccination-induced P. berghei immunity is essentially due to the antibody response, whereas the bactericidal activity of macrophages and the cell-mediated immunity do not play a determinant role.     

H-2-linked Gene(s) Influence the Granulomatous Reaction to Viable Mycobacterium lepraemurium in the Mouse

The genetic control of the granulomatous response to viable Mycobacterium lepraemurium (MLM) was studied in C3H and C57BL/6 inbred strains, BXH recombinant inbred strains, (C3H X C57BL) F1 hybrids, and backcross mice. The results indicate that an autosomal dominant gene, or linked complex of genes, has a marked influence on the footpad reaction to viable MLM. The distribution of responders and non-responders among 12 BXH recombinant inbred strains and linkage analysis in C3H X (C3H X C57BL)F1 backcross mice indicated that the response gene(s) are linked to the H-2 complex on chromosome 17. The same gene(s) also influence host restriction of MLM multiplication and thus appear to be the first H-2-linked gene(s) influencing resistance to a bacterial infection.     

Effect of genetic modification of antibody responsiveness on resistance to Toxoplasma gondii infection.

Resistance to Toxoplasma gondii infection was studied in the high (H/f) and low (L/f) antibody responder lines of mice that were selected on the basis of quantitative antibody responsiveness to the flagellar antigen of Salmonella (selection III). No interline difference was observed in resistance to a highly virulent strain of T. gondii. In contrast, H/f mice were much more resistant than L/f mice to a moderately virulent strain of T. gondii: a 5000-fold difference in terms of the 50% lethal dose was found. The degree of resistance in (H/f X L/f)F1 hybrids was intermediate compared with that in parental lines for both mortality and survival time. The antibody titers to Toxoplasma antigens measured during the course of the infection were significantly higher in H/f than in L/f mice. This interline difference was underestimated because parasite multiplication occurs faster in L/f mice, which increases antigenic stimulation. The stronger resistance of H/f mice is probably due to their higher capacity of antibody production in the course of infection.     

Characterization of the antibody response in inbred mice to a high-molecular-weight polysaccharide from Pseudomonas aeruginosa immunotype 1.

We explored the genetic basis for the differing immune responses observed in inbred strains of mice to a high-molecular-weight polysaccharide (PS) from Pseudomonas aeruginosa immunotype 1 (IT-1). Previous studies have shown that C3H mice immunized with this antigen produce only immunotype-specific antibody. BALB/c mice immunized with IT-1 PS produce both anti-IT-1 PS antibody and antibody cross-reactive with PS from P. aeruginosa immunotype 2 (IT-2). In the current study, we observed that, in addition, these two strains differ in their ability to respond to low immunizing doses of IT-1 PS. C3H mice generated a protective antibody response after a 1-microgram immunization, whereas BALB/c mice failed to produce protective antibody after receiving 1 microgram of PS. Both strains generated protective levels of antibody after a 50-micrograms immunization. Genetic analysis of these response patterns indicates that the ability to produce cross-reactive antibody and the ability to respond to a 1-microgram immunization are independently inherited traits. In addition, the responsiveness of C3H mice to a 1-microgram immunization with the production of protective levels of antibody is not linked to the mouse major histocompatibility (H-2) complex, to sex-linked genes, or to a single gene outside the H-2 complex.     

Genetic control of immune response to staphylococcal exfoliative toxin A in mice.

Different inbred and congenic resistant strains of mice were immunized with staphylococcal exfoliative toxin A (ETA). In antibody responses measured in sera of mice by a passive hemagglutination technique, A/J, DBA/2, BALB/c, B10A, B10D2, B10S, and A.SW were high responders. C57BL/10 (B10), A.BY, and DBA/1 were low responders. The congenic C3H/HeJ and C3H.SW mice were, respectively, high and low responders. The observation that the immune responses of the mice to ETA were closely linked with the haplotypes of their H-2 complexes suggests the existence of an H-2-linked immune response (Ir) gene coding for the production of humoral antibodies to ETA. Four B10A recombinants were used to map this gene within the H-2 complex. The finding that B10A(2R) and B10A(4R) were high responders, whereas B10A(3R) and B10A(5R) were low responders, indicates that the gene controlling antibody response to ETA is located in the I-A subregion or the H-2K end within the H-2 complex. We wish to propose the name Ir-ETA for this gene. The function of Ir-ETA seems to be at least related to antigen recognition at the T-lymphocyte level. Neonatal mice are generally susceptible to ETA regardless of their H-2 haplotypes. However, the neonatal mice born to a high-responder mother immunized with ETA were resistant to the subcutaneous challenge of ETA, but those born to an immunized low-responder mother were susceptible to the challenge. This result suggests that if the mother is a high responder to ETA and is effectively immunized with ETA, the maternal immunity makes it possible to neutralize this toxin in neonatal mice.     

Nonspecific genetic regulation of antibody responsiveness in the mouse.

Four lines of mice were produced by selective breeding for quantitative agglutinin responsiveness to flagellar (f) or somatic (s) antigens (Ags) of Salmonellae: high (H) or low (L) responder lines to fAg and H and L responder lines to sAg. The Salmonellae contained both f and sAgs, the Ag used to perform the selection was the Selection Ag and the other was the Associated Ag. The selective breeding produced a progressive interline separation with an equivalent effect for both Ags. After 15 generations (F15) the level of agglutinin response was about 60 times higher in H than in L responders. About 50% of the phenotypic variation of the character investigated is determined by a group of immune response genes, the rest is due to environmental factors. The nonspecific effect of this group of immune response genes was investigated by measuring the responses to three independent antigens: Sheep erythrocytes (SE), dinitrophenyl-conjugated human IgG (DNP-HGG) and bovine IgG (BGG). The selection for fAg response produced an equivalent modification in the respnsiveness to the Associated Ag (97%) and to BGG (130%). This nonspecific effect was smaller for responsiveness to SE and DNP-HGG, 58% and 41% of the Selection Ag response, respectively. The selection for sAg response produced a nonspecific modification of responsiveness of 94% for the Associated Ag of 74% for BGG and 63% for DNP-HGG. An important exception concerned SE to which an equal antibody response is produced in high and low lines of sAg selection.     

Genetic control of mouse antibody production to human thyroglobulin

Genetic control of immune responses in mice against human thyroglobulin was studied using the enzyme-linked immunosorbent assay and passive haemagglutination test. Our results revealed that mice of H-2a, H-2d, H-2q, H-2k and H-2r haplotypes were high responders for antibody production to human thyroglobulin, while mice of H-2b and H-2s haplotypes were low responders. High responsiveness to human thyroglobulin was transmitted to F1 mice in a dominant fashion. Study of the genetic mapping of the immune responses to human thyroglobulin using various congenic mice showed that I-A subregion gene(s) control the immune response to human thyroglobulin.     

Selective breeding of mice for antibody responsiveness to flagellar and somatic antigens of Salmonellae

Selective breeding has been performed in mice for their high or low antibody responsiveness to Salmonella antigens (Ag). Two noncross-reacting Salmonellae (S. typhimurium and S. oranienburg) have been alternately used to immunize successive generations in order to avoid interference of maternally transmitted antibody. Both Salmonellae carry two independent antigens: flagellar (f) and somatic (s). Two two-way selections were carried out: one for agglutinin response to fAg and the other for agglutinin response to sAg (Selection Ags). The agglutinin response to the other independent Ag was also measured (Associated Ags). The phenotypic character chosen for selection is the maximal agglutinin titer in response to optimal immunization. In both selections, high and low responder lines diverged progressively. There was a 27-fold interline difference in the F₁₃ generation of selection for fAg response and a 38-fold one in the F₁₁ generation of selection for sAg response. This divergence and the continuous distribution of phenotypes in the foundation population indicate that the quantitative character investigated is subject to polygenic regulation. The realized heritability (h²) of the character, measured from the interline divergence, was 0.18 ± 0.06 in both f and s selections. This means that about 20 % of the phenotypic variance of the foundation population is additive. The modification of immune responsiveness to the selection Ag produced by selective breeding was accompanied by a parallel and equivalent effect on immune responsiveness to the noncross-reacting Associated Ag. This effect is therefore entirely nonspecific. A small but definite sex effect in favor of female antibody responsiveness was demonstrated. The results are discussed in comparison with other selection experiments made in mice for quantitative antibody response to other antigens.     

Effects of major histocompatibility complex on autoimmune disease of H-2-congenic New Zealand mice

Autoimmune-prone NZB mice mainly produce IgM-class anti-DNA antibodies and mild SLE develops later in life. The F1 hybrid of NZB and non-autoimmune NZW mice (NZB/W F1 mice) develop a more fulminant SLE, associated with decreases in IgM class, and, in turn, increases in IgG class anti-DNA antibodies. To elucidate the role of the H-2 complex in this mode of anti-DNA antibody production, we established and studied H-2-congenic New Zealand mice, i.e. NZB, NZW, and NZB/W F1 mice with either the homozygous H-2z/H-2z or H-2d/H-2d haplotype or the heterozygous H-2d/H-2z haplotype. The data showed that: (i) although the non-H-2-linked NZB gene(s) seems to determine the IgM anti-DNA antibody production in NZB mice, the effect of this gene is fully expressed only in the case of the H-2d/H-2d homozygous state. (ii) The production of IgG anti-DNA antibodies observed in NZB/W F1 hybrid mice is restricted to the H-2d/H-2z heterozygosity. (iii) Because both NZB and NZW mice with the H-2d/H-2z haplotype produce a lower titer of IgG anti-DNA antibodies than do the NZB/W F1 mice, other complementary non-H-2-linked genetic elements from both NZB and NZW parents are required. The development of lupus nephritis correlated well with that of anti-DNA antibodies. Thus, H-2d/H-2z heterozygosity is a necessary but not sufficient condition for the development of autoimmunity in NZB/W F1 mice.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genetic control of antinuclear antibodies in mice inoculated with the moloney leukaemia virus

The production of antinuclear antibodies (ANA) was studied after inoculation with Moloney leukaemia virus (M-MuLV) in different H-2 congenic strains of mice. Using a new sensitive method for ANA detection, it was demonstrated that M-MuLV-induced ANA were genetically controlled by several different factors. A high viral production was first required for ANA triggering. Among viremic animals both high and low ANA producers were observed. H-2 and non H-2-linked genes were involved in the control of M-MuLV-induced ANA; these genes were different from those involved in the control of viremia. The H2b haplotype was associated with an increased ANA response, the transmission of the responder phenotype being intermediate. Non-H-2-linked genes must also control M-MuLV-induced ANA, as demonstrated in mice having the same H-2 haplotypes, since with equivalent viremias they produced different amounts of ANA. No linkage with X chromosome was found.     

Grenetic Control of Primary and Secondary IgG Responses to Sheep Erythrocytes in Mice

The genetic control of the primary and secondary IgG responses to sheep erythrocytes has been studied by using inbred, H-2-congenic, and intra-H-2-recombinant mouse strains. According to our results, the primary IgG respone is under multi-genic control. There is a correlation, however, between the titer of primary IgG antibodies produced and the H-2 phenotypes among the mouse strains tested. One H-2-linked gene maps at the I-B subregion, whereas another gene can be mapped at or closely linked to the H-2D region. Low and high responsiveness were associated with H-2^b, H-2^f and H-2^a, H-2^d, H-2^k phenotypes, respectively. By comparison of the responses of inbred and congenic strains having the same H-2 phenotype, it can be concluded that background genes influence the primary response only slightly but have almost complete control over the secondary response.     

Genetic regulation of IgE and agglutinating antibody synthesis in lines of mice selected for high and low immune responsiveness

The responses to a wide dose-range of ovalbumin (OV) have been comparatively studied in terms of IgE and hemagglutinating antibodies in high line (HL), low line (LL) and interline cross mice. The kinetics of the primary and secondary responses, which differ according to the antigen dose injected, are parallel in each line, for both types of antibody with the exception of a greater susceptibility of IgE to suppression after higher doses. The threshold doses of antigen which are quite different in HL, LL and F₁ mice are, in each case, similar for both IgE and hemagglutinating antibody induction. Furthermore, in primary response, the dominance effect in F₁ is of “low responsiveness” for 0.05 μg OV and of “high responsiveness” for 0.5 μg OV. The inversion of dominance occurs at the same OV dose for IgE and hemagglutinating antibodies. This is also true for minor doses in secondary response. When individual responsiveness to a minute dose of OV is investigated in interline F₂ and backcross mice, a high correlation coefficient is observed between IgE and hemagglutinating antibodies. Finally, the frequency distribution curves of responsiveness to a minute dose of OV (0.05 μg)in HL, LL, F₁, F₂ and backcross mice are compatible with the hypothesis of a one locus regulation for both IgE and hemagglutinating antibody synthesis.     

Genetic restriction of immune responsiveness to synthetic peptides corresponding to sequences in the pre-S region of the hepatitis B virus (HBV) envelope gene

Proteins of the HBV envelope (env) are coded for by two adjacent regions of the HBV env gene: the pre-S and S regions. Antigenic determinants corresponding to amino acid sequences of both regions are recognized by human antibodies and are important in virus-neutralizing responses. Protective immune responses to HBV appear to be linked to the major HLA histocompatibility complex. Inbred and congenic strains of mice represent a model system relevant for studies on the genetic control of immune responsiveness of humans to HBV envelope proteins. Such mouse strains were ranked according to their antibody response to the S protein and divided into high [d,q], intermediate [a,k,b], and low [s] responders (letters in brackets indicate H-2 haplotype.) Selected pre-S antigenic determinants can be mimicked with high fidelity by synthetic peptide analogues that are immunogenic without any carriers. Thus it is possible to study directly the genetic control of immune responsiveness to pre-S epitopes mimicked by these peptides without having to consider the influence of carriers or of S protein. The results presented here show that inbred mouse strains can be ranked according to their antibody responses to the synthetic peptide pre-S(120-145) as follows: A/J[a] approximately equal to SWR/J[q] greater than C57BL/6J[b] approximately equal to AKR/J[k] approximately equal to SJL/J[s] much greater than DBA/2J[d] greater than BALB/cJ[d]. Only SJL/J[s] mice responded well to another synthetic peptide pre-S (12-32). Thus, H-2-linked genes regulating the immune response to S protein and to epitopes on pre-S-coded sequences are distinct. Anti-pre-S(120-145) responses in S protein-nonresponders circumvent this nonresponsiveness. This should be considered in the design of hepatitis B vaccines.     

Cell-mediated anti-tumor response in the RL♂61 system II. Control of the T killer cells by an H-2-linked Ir gene interfering with non-H-2 factors

The generation of cytolytic T lymphocytes (CTL) during the immune response directed against the syngeneic X-ray-induced BALB/c RL♂ 1 leukemia has been described previously: T killer cells react with a tumor antigen of RL♂ 1 cells, and the H-2D^d molecules of the target cells play some role in the interaction. The study of anti-RL♂ 1 responses of [(C57BL/6 × BALB/c) × BALB/c] mice shows that the major histocompatibility complex controls the anti-RL♂ 1 CTL reaction at a second level, through an Ir gene, with dominant responsiveness, probably mapping to the right of I-B and controlling the high or low-CTL responder phenotype. Another non- H-Associated gene interferes with the H-2-linked Ir gene, a responder allele at the non-H-2 locus, being necessary for the expression of the high-responder phenotype at the Ir gene locus.     

Potentialities of immunocompetent cells in high and low antibody-producing lines of mice obtained by selective breedings for responsiveness to flagellar or somatic antigens of Salmonellae

The genetic modifications of immunocompetent cell functions were investigated in high (H) and low (L) antibody responder lines of mice obtained by selective breeding for responsiveness to flagellar and somatic antigens of Salmonellae (Selection III and Selection IV, respectively). Several lines of evidence converge to demonstrate that the differences in antibody responses between the H and L lines of the two selections are not due to the modification of antigen handling by macrophages. This contrasts with previous observations that macrophages play a major role in interline differences in Selections I and II. The choice of antibody titres after secondary challenge as the phenotypic character in Selections III and IV may explain why the regulatory role of macrophages was minimized, compared with Selections I and II which were carried out for primary responses to heterologous erythrocytes. In Selections III and IV, H mouse lymphocytes were more efficient than L mouse lymphocytes in restoring immunoresponsiveness to irradiated hosts. In contrast, allogeneic skin grafts were rejected at a similar rate in L as well as in H mice of the two Selections and in vitro lymphoproliferative responses to T cell mitogens were also equivalent in the four lines.     

Genetic control of contact sensitivity to oxazolone in inbred,H-2 congenic and intra-H-2 recombinant strains of mice

Delayed-type hypersensitivity (DTH) to 2-phenyl-4-ethoxymethylene-5-oxazolone (oxazolone) was found to be under multigenic control in inbred, H-2 congenic and intra-H-2 recombinant strains of mice. A high response was associated with haplotypes H-2^d,a,k and low response with haplotype H-2^b. DTH to oxazolone was high or intermediate in different F₁ hybrids of high and low responder mice. In F₂ and backcross generations a higher response was associated with the “dd”, than with the “bb” phenotype, while intermediate response was found in the heterozygote “db” mice. A study of H-2 recombinant strains suggests that a gene controlling the DTH response maps in the I-B subregion of the H-2 complex. The response was significantly modified by gene(s) which are not linked to the H-2 complex and have not been mapped. Since congenitally athymic nude (nu/nu) mice did not respond to oxazolone, this contact sensitivity is belived to be a T cell-dependent immune response.     

H-2-linked genetic control of antibody response to soluble calf skin collagen in mice

An autosomal dominant immune response gene could be demonstrated in congenic resistant strains of mice which is linked to the H-2 locus and controls the antibody response to soluble calf collagen. High responsiveness was associated with the H-2 alleles, b and f, low responsiveness with the H-2 alleles, d, k, m and r. Studies with calf procollagen, which contains an additional carrier moiety, indicated that these genetic differences might be expressed at the level of T cells.