Genetic control of the immune response

(1) Inbred strains of mice when immunized withp-aminobenzoic acid and sulphanilic acid bound by diazo-linkage to the same protein carrier molecule (bovine gamma globulin) differ in their ability to respond by antibody formation. The strains A and CBA/J form only low levels of antibodies to the haptens after immunization; in strains ScSN and B10.LP the same high titers of antibodies to both haptens were found under these conditions. The strain B10.D₂ forms antibodies well to sulphanilic acid, antip-aminobenzoic acid antibodies are formed only in very low quantity. (2) Individual mice of an inbred strain form a homogeneous population in respect of their capability or inability to form a particular antihapten antibody. The individual titers in a given inbred strain vary only slightly. On the contrary the noninbred strain H shows great variability both in quantity and quality of the immune response to the haptens. (3) The crossing of good and poor anti-hapten antibody producing strains shows in F₁; F₂ and B₁ generation, that the ability to produce antibodies againstp-aminobenzoic and sulphanilic acid depends on the genotype of a given individual. The ability to respond is transmitted to the offspring as a dominant trait. (4) There is no difference in the response to the haptens between males and females of the same strain. (5) The antibodies to the haptens in different strains of mice differ in the ratio of 2-mercaptoethanol sensitive and 2-mercaptoethanol resistant antibody. Dedicated to Academician Ivan Málek on the occasion of his 60th birthday     

Genetic control of the immune response

The participation of cells from bone marrow and thymus in the antibody response to haptens was studied in two inbred strains of mice: poorly (CBA/J) and well (B10.LP) responding to immunization. The cell transfer experiments showed that the genetic regulation of the antihapten response under study, was bound directly to lymphatic cells of the immune system. For transfer of the good response it was essential that the thymus and bone marrow cell mixture contained bone marrow cells from well responding donors. Furthermore, the effect of endotoxin on antibody formation was studied in both well and poorly responding strains. It was found that endotoxin enhanced the antibody formation in both strains similarly so that the finεl differences between the levels of antibodies formed in both strains remained unchang d. Finally, it was demonstrated that endotoxin played the most important role in the primary stimulation, where the highest increase of the antibody response was obtained.     

Genetics of resistance to the African trypanosomes. III. Variant-specific antibody responses of H-2-compatible resistant and susceptible mice

Genetically based differences in variant-specific immunity to the African trypanosomes were examined. H-2-compatible inbred mouse strains that differed in relative resistance were infected with Trypanosoma rhodesiense clone LouTat 1. Antibody responses to exposed epitopes of the LouTat 1 variant-specific surface glycoprotein (VSG) were measured. Relatively resistant B10.BR mice (H-2k) made predictable IgM antibody responses to the VSG of LouTat 1 which were associated with clearance of the LouTat 1 variant antigenic type from blood; IgG responses to LouTat 1 surface antigen appeared after clearance occurred, and were lower than peak titers of IgM. Intermediately susceptible CBA mice (H-2k) also made predictable IgM and IgG responses which followed the same pattern as the more resistant strain. Peak titers were lower for both Ig classes, however, and a delayed appearance of antibody was correlated with delayed clearance of LouTat 1. In contrast to B10.BR and CBA mice, the susceptible C3H mice (H-2k) failed to make detectable antibodies to LouTat 1 surface antigen and also failed to control the first peak of parasitemia. The absence of immunity in infected C3H mice was selective for antibody to exposed epitopes of LouTat 1 VSG because antibody was detectable to invariant VSG or internal trypanosome antigens. Also, the C3H strain was shown not to be a genetic nonresponder to LouTat 1 surface antigen because VSG-specific antibodies appeared within 1 wk after trypanocidal chemotherapy. Finally, we demonstrated that the susceptibility of C3H mice was not associated with an inability of the mononuclear phagocyte system to clear the parasites because drug cure, passive transfer of immune serum, or sensitization of trypanosomes with antibody all led to trypanosome clearance from blood by the liver. In summary, we show for the first time that major differences in variant-specific immunity occur in MHC-compatible animals after infection with the African trypanosomes.     

The immune response of the mouse to lymphocytic choriomeningitis virus. IV. Enumeration of antibody-producing cells in spleens during acute and persistent infection

The solid-phase immunoenzymatic technique for the enumeration of single rat cells producing antibodies against ovalbumin has been adapted to mouse cells producing antibodies against lymphocytic choriomeningitis (LCM) virus. After intravenous (i.v.) infection with 10(3) infectious units, IgM- and IgG-producing cells appeared on days 4 and 5, respectively. They rose to high numbers on days 7, 8, and 9 and were still detectable on day 38. After a second i.v. inoculation of 10(7) infectious units, antibody-producing cells (APC), most of which made IgG, appeared faster and reached much higher numbers. Mutatis mutandis, very similar results were obtained with mice inoculated with vesicular stomatitis virus. Antibodies were specific as to virus, but probably corresponded to more than one viral antigen. Relatively low numbers of APC were also detected in the spleens of NMRI strain carrier mice, which develop severe immune complex disease in later life, but not in spleens of persistently infected young mice of strains that remain free of late immune complex disease, namely CBA/J, C3H/HeJ, and gray house mice; APC were detected in spleens of aging CBA/J but not gray house mice.     

Genetic Determination of the Developmental Program for Mouse Liver β-GALACTOSIDASE: Involvement of Sites Proximate to and Distant from the Structural Gene

The identification and mode of action of genetic loci that program gene expression during development are important for understanding differentiation in higher organisms. Previous work from this laboratory has identified two patterns for the postnatal development of liver beta-galactosidase among inbred mouse strains: type I, where activity levels remain constant after about 30 days of age, is found in strains DBA/2J, CBA/J, and BALB/cJ, among others; type II, where activity levels increase between 25 and 50 days of age to reach a new adult level, is found in strain C57BL/6J and related strains. It has been shown that the type I vs. type II developmental difference between strains C57BL/6J and DBA/2J is due to variation at a locus, Bgl-t, that maps with the beta-galactosidase complex, [Bgl], on chromosome 9. In the present study, we have confirmed the existence of Bgl-t as a temporal locus within [Bgl] by analysis of both a congenic strain carrying the beta-galactosidase complex of strain CBA/J in the C57BL/6J genetic background and a cross of strains CBA/J and C57BL/6J. The existence of additional temporal loci for beta-galactosidase that segregate independently of the structural gene and participate in determination of the type I vs. type II difference was revealed by analysis of: (1) a congenic strain containing the beta-galactosidase complex of strain BALB/cJ in the C57BL/10Sn background; (2) recombinant inbred lines derived from progenitor strains C57BL/6ByJ and BALB/cByJ; and (3) a genetic cross between strains C57BL/6ByJ and BALB/cByJ. Thus, for these pairs of strains, the type I vs. type II developmental difference is due to variation at a temporal locus (or loci) unlinked to the enzyme structural gene, and not at Bgl-t. These facts, together with information gathered from an examination of the distribution of beta-galactosidase phenotypes among over 100 inbred strains (Breen, Lusis and Paigen 1977), have led us to conclude that the postnatal developmental pattern for liver beta-galactosidase is determined by a set of interacting temporal genes. One of these, Bgl-t, is located within [Bgl], and one or more are separable from [Bgl] by recombination. A possible mode of interaction among the temporal and instructural loci is suggested.     

Immune responses of different mouse strains after challenge with equivalent lethal doses of Toxoplasma gondii

Most immunological studies that utilize different strains of inbred mice following T. gondii infection fail to compensate for differences in host susceptibility to the size of the parasite innoculum. To address this concern, susceptible C57BL/6 and resistant CBA/J mice were orally infected with either an equivalent 50% lethal dose (LD50) of brain cysts of the 76K strain of T. gondii (15 cysts in C57BL/6, 400 cysts in CBA/J) or the same dose of parasites in each mouse strain. C57BL/6 mice receiving 400 cysts (LD50 of CBA/J mice) died post infection, whereas CBA/J mice that received 15 cysts (LD50 of C57BL/6 mice) survived. Parasite loads in the brains and serum Toxoplasma-specific IgG1 titers of LD50-infected C57BL/6 mice were significantly higher than those in LD50- or 15 cysts-infected CBA/J mice, whereas splenocyte proliferation to Toxoplasma antigen and the percentage of CD8 alpha+ T cells were reduced in LD50-infected C57BL/6 mice. In contrast, serum IgG2a and IgM titers, the percentage of gamma delta T cells and IFN-gamma expression of spleen of LD50-infected CBA/J mice were higher than those of either 15 cysts-infected CBA/J mice or LD50-infected C57BL/6 mice. These observations demonstrate that the immune response between LD50-infected C57BL/6 and CBA/J mice was more prominent when compared to C57BL/6 or CBA/J mice receiving the same parasite inoculum. These observations would suggest that caution must be excersized in the planning and interpretation of data when the size of the parasite inoculum has not been adjusted for mouse strain.     

Dominant low responsiveness in the IgG response of mice to the complex protein antigen type 1 fimbriae from Actinomyces viscosus T14V.

Type 1 fimbriae from Actinomyces viscosus T14V, composed of a complex protein of Mr 65,000, mediate the adherence of A. viscosus T14V to the host, whereas type 1 fimbriae-specific antibodies inhibit adherence. Genetic control of the serum IgG response to type 1 fimbriae was evaluated in a series of inbred, hybrid, recombinant inbred, and back-cross mice. Mice were given i.p. injections of 10(8) A. viscosus T14V cells in saline on days 0 and 14, and IgG anti-type 1 fimbriae in sera obtained on day 26 were measured by ELISA. Segregation analysis of the responses of (BALB/cJ x A/J)F1 x A/J backcross mice suggested polygenic control. Linkage analysis in (BALB/cJ x A/J)F1 x A/J backcross and SWXL recombinant inbred mice suggested control by genes linked with H-2 and with Ly-17 and Akp-1. In several F1 hybrid strains derived from H-2-disparate high and low responder parental strains, low responsiveness was dominant. The F1 derived from the H-2-identical high and low responder strains CBA/J and C3H/HeJ was a low responder, suggesting that dominant low responsiveness was mediated by non-H-2-linked genes. A three-gene model is proposed for regulation of the type 1 fimbriae response, including an MHC-linked gene, a gene linked with Ly-17 and Akp-1 on the telomeric portion of chromosome 1, and a background gene whose linkage is unknown.     

Trypanosoma cruzi: serum antibody reactivity to the parasite antigens in susceptible and resistant mice

The specific antibody responses were compared among susceptible (A/Sn), moderately susceptible (Balb/c) and resistant (C57 BL/10J) mice infected with Trypanosoma cruzi (Y strain). Sera obtained during the second week of infection recognized a surface trypomastigote antigen of apparent Mr 80 kDa while displaying complex reactivity to surface epimastigote antigens. Complex trypomastigote antigens recognition was detected around the middle of the third week of infection. No major differences were observed along the infection, among the three strains of mice, neither in the patterns of surface antigen recognition by sera, nor in the titres of antibodies against blood trypomastigotes (lytic antibodies), tissue culture trypomastigotes or epimastigotes. On immunoblot analysis, however, IgG of the resistant strain displayed the most complex array of specificities against both trypo and epimastigote antigens, followed by the susceptible strain. IgM antibodies exhibited a more restricted antigen reactivity, in the three mouse strains studied. Balb/c sera (IgG and IgM) showed the least complex patterns of reactivity to antigens in the range of 30 kDa to 80 kDa. The onset of reactivity in the serum to trypomastigote surface antigens was also dependent on the parasite load to which the experimental animal was subjected.     

Isolates of Candida albicans that differ in virulence for mice elicit strain-specific antibody-mediated protective responses

Three distinct isolates of Candida albicans were used to establish systemic and oral infections in inbred mice that are genetically resistant or susceptible to tissue damage. Patterns of infection differed significantly between both yeasts and mouse strains. Systemic infection conferred significant protection against re-challenge with the homologous, but not the heterologous yeast; however, the protective effect was more evident in the tissue-susceptible CBA/CaH mice than in the resistant BALB/c strain. In contrast, oral infection induced protection against both homologous and heterologous oral challenge, although this was significant only in the CBA/CaH mice. CBA/CaH mice produced antibodies of both IgG1 and IgG2a subclasses, whereas BALB/c mice produced predominantly IgG1. Western blotting demonstrated considerable differences between epitopes recognised by serum antibodies from mice of both strains after immunisation with each of the three yeasts. Thus, different strains of yeast show considerable specificity in antibody responses elicited by either systemic or oral infection.     

Characterization and sequence analyses of antibody-selected antigenic variants of herpes simplex virus show a conformationally complex epitope on glycoprotein H.

Thirteen antigenic variants of herpes simplex virus which were resistant to neutralization by monoclonal antibody 52S or LP11 were isolated and characterized. The antibodies in the absence of complement potently neutralize infectivity of wild-type virus as well as inhibit the transfer of virus from infected to uninfected cells ("plaque inhibition") and decrease virus-induced cell fusion by syncytial strains. The first variant isolated arose in vivo. Of 66 type 1 isolates analyzed from typing studies of 100 clinical isolates, one was identified as resistant to neutralization by LP11 antibody. The glycoprotein H (gH) sequence was derived and compared with those of wild-type and syncytial laboratory strains SC16, strain 17, and HFEM. The sequences were highly conserved in contrast to the diversity observed between gH sequences from herpesviruses of different subgroups. Only four coding changes were present in any of the comparisons, and only one unique coding change was observed between the laboratory strains and the clinical isolate (Asp-168 to Gly). These sequences were compared with those of antigenic variants selected by antibody in tissue culture. Twelve variants were independently selected with antibody LP11 or 52S from parent strain SC16 or HFEM. For each variant, the gH nucleotide sequence was derived and a point mutation was identified giving rise to a single amino acid substitution. The LP11-resistant viruses encoded gH sequences with amino acid substitutions at sites distributed over one-half of the gH external domain, Glu-86, Asp-168, or Arg-329, while the 52S-resistant mutant viruses had substitutions at adjacent positions Ser-536 and Ala-537. One LP11 mutant virus had a point mutation in the gH gene that was identical to that of the clinical isolate, giving rise to a substitution of Asp-168 with Gly. Both LP11 and 52S appeared to recognize distinct gH epitopes as mutant virus resistant to neutralization and immunoprecipitation with LP11 remained sensitive to 52S and the converse was shown for the 52S-resistant mutant virus. This is consistent with previous studies which showed that while the 52S epitope could be formed in the absence of other virus products, virus gene expression was required for stable presentation of the LP11 epitope, and for transport of gH to the cell surface (Gompels and Minson, J. Virol. 63:4744-4755, 1989). All mutant viruses produced numbers of infectious particles that were similar to those produced by the wild-type virus, with the exception of one variant which produced lower yields.(ABSTRACT TRUNCATED AT 400 WORDS)     

Immunogenetic studies of spontaneous abortion in mice. II. Antiabortive effects are independent of systemic regulatory mechanisms

CBA/J females (H-2k) mated with DBA2/J males (H-2d) exhibit a high rate of fetal resorption. Fetal survival has been improved by pretreatment of CBA/J females with spleen cells from BALB/c J (H-2d) (but not from CBA/J or DBA/2/J) males. Similarly, three out of nine recombinant inbred strains (recombining BALB/c and DBA2 genomes at the homozygous state) possess antiabortive effects like the BALB/c parent. Previous studies showed that BALB/c pretreatment triggers the appearance of suppressor cells in the spleen and of IgG1 anti-H-2d antibodies in the serum of CBA/J females. Studies of these two immunological parameters after CBA/J preimmunization by the different recombinant strains suggest that local intrauterine immunoregulation is the determinant of success or failure of allopregnancy.     

Immune Response against Hamster Erythrocytes in the Low-Responder Mouse Strains

In a previous paper we reported that an inbred strain of SL mice and an outbred strain of CF1 mice belonged to the high-responder strains in antibody production after primary immunization with hamster erythrocytes (H-RBC), while inbred strains of C57BL/6, AKR and C3H/He mice belonged to low-responder strains. In the present study we obtained the following results. 1) Pre-sensitization with hamster lymphoma enhanced antibody production after an intravenous injection of H-RBC. There was no strain difference in the pattern of antibody production against H-RBC among pre-sensitized mice. 2) The pattern of enhanced antibody production after an intravenous injection of H-RBC into pre-sensitized mice assumed the primary type in terms of time of appearance of hemolysin plaque-forming cells (PFC) in the spleens and the conversion from 2-mercaptoethanol sensitive to 2-mercaptoethanol resistant antibody production, when the intervals between both treatments were within 7 days. 3) Pre-sensitization with lymphoma induced not only an increase in numbers of PFC after an intravenous injection of H-RBC, but also an increase in the size of the hemolysin plaques. These results suggested that sensitization with hamster lymphoma stimulated some kinds of immuno-competent cells, which could contribute to antibody production against H-RBC after a booster injection of H-RBC.     

Influenza virus-susceptible mice carry Mx genes with a large deletion or a nonsense mutation.

The interferon-regulated mouse Mx gene encodes the 72-kilodalton nuclear Mx protein that selectively inhibits influenza virus replication. Mice carrying Mx+ alleles synthesize Mx protein and resist influenza virus infection, whereas mice homozygous for Mx- alleles fail to synthesize Mx protein and, as a consequence, are influenza virus susceptible. Southern blot analysis allowed us to define the following three distinct Mx restriction fragment length polymorphism (RFLP) types among classical inbred strains: RFLP type 1 in the Mx+ strains A2G and SL/NiA, RFLP type 2 in BALB/c and 33 other Mx- strains, and RFLP type 3 in CBA/J and 2 other Mx- strains. cDNA clones of Mx mRNAs from BALB/c and CBA/J cells were isolated, and their sequences were compared with that of the wild-type Mx mRNA of strain A2G. Mx mRNA of BALB/c mice has 424 nucleotides absent from the coding region, resulting in a frame shift and premature termination of Mx protein. The missing sequences correspond exactly to Mx exons 9 through 11. These three exons, together with some flanking intron sequences, are deleted from the genomes of all Mx RFLP type 2 strains. The Mx- phenotype of the Mx RFLP type 3 strain CBA/J is due to a point mutation that converts the lysine codon in position 389 to a termination codon. Mx RFLP type 3 strains have an extra HindIII site which maps to an intron and thus probably does not affect the coding capacity of Mx mRNA. We further show that the Mx mRNA levels in interferon-treated BALB/c and CBA/J cells are about 15-fold lower than in similarly treated Mx+ cells. This is probably due to decreased metabolic stabilities of the mutant mRNAs.     

Potentiation of immune response against the RESA peptides of Plasmodium falciparum by incorporating a universal T-cell epitope (CS.T3) and an immunomodulator (polytuftsin), and delivery through liposomes.

Synthetic peptides representing repeat sequences of ring-infected erythrocyte surface antigen (RESA) of Plasmodium falciparum have shown poor immunogenicity and protection. In this study, the RESA peptides [(EENVEHDA)2 and (DDEHVEEPTVA)2] were chemically linked to a universal T-cell determinant, CS.T3, derived from the CS protein of P. falciparum. Polytuftsin (TKPR)40, a polymer of naturally occurring immunomodulator "tuftsin," was physically mixed with these conjugates. These preparations in alum and liposomes were immunized in four inbred strains of mice with different genetic backgrounds to study the humoral response. In the case of liposome-entrapped preparations, a 10 microg dose of antigen showed the optimum antibody response. Mice immunized with liposome containing RESA peptide(s)-CS.T3 conjugate along with polytuftsin showed the highest antibody levels in all the strains, whereas the RESA peptide(s) alone, adsorbed on alum or entrapped in liposomes, showed either poor or moderate antibody levels. The antibodies raised against liposome-entrapped preparations in both high-responder strain (SJL/J H-2s) and low-responder strain (FVB/J H-2q) showed 2 4-fold lower Kd values as compared to the alum adsorbed preparations, suggestive of high affinity antibodies. All the antigen preparations predominantly induced IgG2a and IgG2b isotype response, suggesting that the T-helper response involved is of the CD4 Thl type. The in vitro merozoite reinvasion inhibition assay showed 50-92% inhibition with sera raised against different antigen formulations. The highest percentage inhibition was observed with the RESA peptide-CS.T3 conjugate containing polytuftsin in liposomes. Thus, the incorporation of peptide antigens inside liposomes not only reduced the antigen dose by 5-fold but also elicited a high titre with high affinity antibodies and the inhibition of merozoites to RBC in vitro. Therefore, we conclude that the incorporation of these synthetic constructs in liposomes could be a useful strategy for the development of a subunit immunogen against malaria.     

Schistosoma japonicum: Infection characteristics in mice of various strains and a difference in the response to eggs

Female mice of 12 inbred strains were exposed to 20–25 cercariae of Schistosoma japonicum and infection status determined at day 40 by counting numbers of adult worms, eggs in faeces and eggs in a segment of liver. Most mouse strains appeared to be ‘permissive’ hosts although at least one strain (129/J) was shown to be relatively resistant in terms of day 40 adult worm numbers. In a radioisotopic lung assay for sensitivity to eggs, and developed as a rapid means of assessing granuloma formation, CBA/H mice were shown to differ from C57BL/6 mice in being non-responders. Histological examination of lungs of sensitized CBA/H and C57BL/6 mice injected intravenously with eggs established that granuloma formation was much more intense in C57BL/6 than CBA/H mice. Preliminary indications are that infected CBA/H mice are also low anti egg circumoval precipitin (COP) responders. Analysis of immune responses to isolated egg antigens in these two strains, and identification of the antigens of eggs to which such responses are directed in C57BL/6 mice, should provide insights into immunological disease processes (such as granulomatous inflammation) in this model system of japonicum schistosomiasis.     

T-cell responsiveness in Mycobacterium lepraemurium infections in a "resistant" (CBA) and a "susceptible" (BALB/c) mouse strain

Antigen-specific and mitogen-nonspecific T-lymphocyte proliferation and lymphokine release (interleukin 2 and macrophage activation factor) were studied in BALB/c and CBA mice infected intravenously with 10(8) Mycobacterium lepraemurium organisms. The responsiveness of spleen cells from infected animals to Con A and specific MLM antigen declined as the infection progressed. Thus, the decreased responsiveness appeared earlier and was more profound in the relatively susceptible BALB/c strain than in the relatively resistant CBA strain. Nylon-wool-purified, T-cell-enriched spleen cells from both strains, however, responded to both M. lepraemurium antigen and Con A until the later stages of infection (17 weeks postinfection). The relevance of nonspecific immunodepression mediated by nylon-wool-adherent spleen cells to the progressive nature of this infection is discussed.     

Update of mouse microsatellite database of Japan (MMDBJ).

We updated a database of microsatellite marker polymorphisms found in inbred strains of the mouse, most of which were derived from the wild stocks of four Mus musculus subspecies, M. m. domesticus, M. m. musculus, M. m.castaneus and M. m. molossinus. The major aim of constructing this database was to establish the genetic status of these inbred strains as resources for linkage analysis and positional cloning. The inbred strains incorporated in our database are A/J, C57BL/6J, CBA/J, DBA/2J, SM/J, SWR/J, 129Sv/J, MSM/Ms, JF1/Ms, CAST/Ei, NC/Nga, BLG2/Ms, NJL/Ms, PGN2/Ms, SK/CamEi and SWN/Ms, which have not or have only been poorly incorporated in the Whitehead Institute/MIT (WI/MIT) microsatellite database. The number of polymorphic microsatellite loci incorporated in our database is over 1,000 in all strains, and the URL site for our database is located at http:// www.shigen.nig.ac.jp /mouse/mmdbj/mouse.html.     

Inheritance of Plasma Cholesterol Levels in Mice

Mean plasma cholesterol levels were determined at two ages in mice from eight unrelated inbred strains (BALB/cJ, BDP/J, CBA/J, C57BL/6J, LP/J, RF/J, SJL/J, and 129/J). Significant strain, sex, and age differences were observed. Estimates of the degree of genetic determination of the trait obtained from an analysis of the strain data averaged 58 +/- 4% for the males and 54 +/- 8% for the females.-Selection for high and low plasma cholesterol levels produced two significantly different and distinct lines. Selection was initiated in a genetically heterogeneous population derived from an eight-way cross of the inbred strains listed above. After five generations of selection the divergence of the high and low lines amounted to 4 phenotypic standard deviations of the foundation population. Realized heritability estimated from the regression of divergence on the combined cumulative selection differential was 51 +/- 5% for the males and 50 +/- 3% for the females. The results indicate that genetic factors are important in controlling plasma cholesterol levels in the mouse and that the majority of these factors act additively.     

Detection of immunoglobulin heavy chain IgG3 polymorphism in wild mice with xenogeneic monoclonal antibodies

We have generated four xenogeneic rat antimouse IgG₃ monoclonal antibodies recognizing at least three different antigenic determinants (epitopes) on BALB/c IgG₃ molecules. These antibodies were used in solid-phase blocking radioimmunoassays for detection of the epitopes in sera of 40 inbred strains and 134 wild mice. These antibodies detect genetic polymorphism of IgG₃ isotype among wild mice even though there is no polymorphism found among 40 inbred strains tested (except X-chromosome-linked immunodeficient CBA/N strain which lacks IgG₃ molecules). An IgG₃ variant was also isolated from hybridomas derived from Mus spretus.Abbreviations Igh-C immunoglobulin heavy chain constant region - PVC polyvinyl chloride - RIA radioimmune assay - ELISA enzyme linked immunosorbent assay     

Sex and strain differences of mouse variant salivary proteins

Proteins of the mouse saliva are resolved into about 20 discrete bands by polyacrylamide gel electrophoresis. Sexual dimorphism and monomorphism were found in a subset (Msp-1) of these salivary proteins from different inbred strains. This sexual dimorphism involves a fast moving band (F-type) and a slow moving one (S-type). Mature males of seven strains (A/J, AKR, CBA/J, C3H/HeN, A/Sn, B10.A, and B10.BR) exhibit the S phenotype while mature females of these strains were typed as F. Sexually immature males and females of these strains were uniformly typed as F, but at puberty (5-6 weeks of age) the phenotype of the males switched to type S, while the phenotype of the females remained the same. This switch to type S at puberty did not take place in males of four strains (BALB/cAnn, B10.D2, C57BL/6, and C57BL/10); therefore, we conclude that these strains were sexually monomorphic with regard to Msp-1. The phenotype of mature males of C3H/HeN reverted to type F following castration, whereas castrated males and mature females switched to type S in response to testosterone administration. The testosterone treatment had no effect on the type S phenotype of males and females of the sexually monomorphic BALB/cAnn strain. The male-specific type S phenotype of Msp-1 was seen only in mice with H-2 haplotype a or k; thus an association with H-2 haplotype was suggested. All F1 males of reciprocal crosses involving the sexually dimorphic and monomorphic strains (e.g., C3H/HeN X BALB/cAnn) demonstrated the type S phenotype at puberty.