Allelic polymorphism of murine IgE controlled by the seventh immunoglobulin heavy chain allotype locus

Two alloantisera against hybridoma-derived IgE detected allotypic determinants expressed on the murine s chain. An antiserum raised in BALB/c mice against monoclonal IgE of C57BL/6 origin reacted exclusively with IgE of strains having Igh-1^b (IgG_2a) allotype. The second antiserum, C57BL/6 anti-BALB/c monoclonal IgE, reacted with IgE of strains having Igh-1^a, Igh-1^d, Igh-1^e and Igh-1^j allotypes. The genetic studies of (BALB/c x C57BL/6)F₁ and backcross F₂ animals indicated that the locus controlling the IgE allotype is linked to the Igh-1 locus. This was further confirmed by the possession of respective IgE allotypes by Igh-C congenic mice, BALB/c and BAB-14, C3H.SW/Hz and CWB/Hz. Thus, the allotype detected on the chain is controlled by the seventh murine immunoglobulin allotype locus, and should be designated as the Igh-7 allotype.Abbreviations used in this paper PCA passive cutaneous anaphylaxis - RID radioimmunodiffusion - i.p. intraperitoneally - EA egg albumin - Igh-C immunoglobulin heavy chain constant region locus - DNP 2,4-dinitrophenyl - PBS phosphate-buffered saline - NMS normal mouse serum - KLH keyhole limpet hemocyanin Visiting investigator supported by the Scientific and Humanistic Development Council from the Central University of Venezuela, currently at the following address: Consejo de Desarrollo Cientifico y Universidad Central de Venezuela, Av. Principal Urb. La Floresta Ota., Silenia Caracas, Venezuela.     

Teratocarcinoma transplantation rejection loci: Genetic localization of the Gt-1 locus on chromosome 17 and the expression of alternate alleles

A series of congenic mice on the BALB/c genetic background have been employed to localize a teratocarcinoma transplantation rejection locus, Gt-1, to the K side of the H-2 locus on chromosome 17. Previous studies have placed the Gt-1 ^sv allele about 8 centimorgans away from the H-2 ^b or H-2 ^bv1 locus. Teratocarcinomas derived from 129/sv mice, Gt-1 ^sv (H-2K ^bv1/H-2D ^bv1), are rejected by BALB/c (H-2K ^d/H-2D^d) and BALB-G mice (H-2K ^d/H2D-^b, but form tumors in BALB-B (H-2K ^b/H2D ^b) and BALB/5R5 mice (H-2K ^b/H2D ^d). In the reciprocal tumor-rejection test, a BALB/c teratocarcinoma was rejected by immunized BALB·B mice, but formed tumors in the immunized isogenic BALB/c mouse. These studies demonstrate the reciprocal expression of two Gt-1 alleles, one Gt-1 ^c, in BALB/c mice, and the other, Gt-1 ^sv, in the congenic BALB·B mice. Shedlovsky and co-workers have placed the Gt-1 locus in a similar location on the K side of the H-2 locus on chromosome 17.     

The influence of Igh-1 genes on the class and subclass distribution of oxazolone-specific antibodies

Previous studies have demonstrated that the level of the oxazolone-specific antibody response induced by contact sensitization is under the control of H-2 and Igh-1-linked genes. The aim of the present study was to clarify the role of H-2 and Igh-1 genes in the regulation of antibody affinity and isotype composition of oxazolone-specific antibodies. Analysis of the antibody response to oxazolone has revealed different ratios of IgG2a and IgG2b antibodies in mice carrying the Igh-1 ^b allele and in strains carrying alleles a, c, and e. The characteristic ratio of IgG2a and IgG2b isotypes persisted during the whole period of the primary and secondary antibody response of CBA and CBA-Ig ^b Igh-C congenic mice. The Igh-1-linked genes influenced the isotype distribution and not the affinity of oxazolone-specific antibodies induced by contact sensitization.Abbreviations used in this paper c.Ig chicken immunoglobulin - Igh-C constant region of immunoglobulin heavy chain - DNCB 2,4-dinitrochlorobenzene - DTH delayed-type hypersensitivity - FITC fluorescein isothiocyanate - Igh-1 cluster of structural heavy chain allotype genes of IgG2a - KLH keyhole limpet hemocyanin - KSCN potassium-sulfocyanid - MHC major histocompatibility complex - Ox oxazolone (4-ethoxymethylene-2-phenyl-5-oxazolone - Ox-BSA oxazolone-bovine serum albumin - Ox-cap oxazolone-capronic acid - Ox-MSA oxazolone-mouse serum albumin - NP 4-hydroxy-3nitrophenyl acetyl - PVP polivinylpirrolidon - RIA radioimmunoassay - SRBC sheep red blood cell - T_H T helper - T_S T suppressor - Igh-V variable region of immunoglobulin heavy chain     

Genetic and functional analyses of the primary in vitro CTL: Response of NZB lymphocytes toH-2-compatible cells

Spleen cells from NZB mice make an unexpected primary cytotoxic T lymphocyte (CTL) response to BALB/c cells in vitro. In this study, it is shown that this response is comprised of at least three independent components. These include a response to antigens recognized in association with H-2^d products, a response to Qa-1^b-associated antigens which is notH-2-restricted and a response directed toward antigens not associated with either H-2^d- or Qa-1^b-coded determinants. The last response appears to be the weakest of the three. In addition, cells from NZB F₁ mice which were either homozygous (Qa-1 ^a /Qa-1 ^a ) or heterozygous (Qa-1 ^a /Qa-1 ^b ) forQa-1 alleles, all responded to BALB/c cells. These data suggest that the NZB CTL response to BALB/c cells is not solely dependent on antigens coded for by genes in theH-2D-Tla region for either the sensitization or effector phases of the response. The ontogeny of the NZB anti-BALB/c CTL response coincides with that of a number of B-cell abnormalities but is shown in experiments with-suppressed NZB mice to be independent of B-cell dysfunction. Studies with (NZB x B10.D2)F₁ + B10.D2 mice demonstrated that the anti-BALB/cCTL response to antigens coded for outside ofQa-1 is governed by at least two genes. Finally, it is shown that another conventionallyH-2-restricted response, that to TNP-modified isologous cells, is neither significantly cross-reactive nor markedly elevated in NZB mice. — The foregoing observations suggest that some subsets of NZB T lymphocytes are intrinsically abnormal. The possibilities that the apparent hyperreactivity of NZB CTL precursors, evidenced in the response to BALB/c cells, is primary or results from the secondary effects of excess T-cell help are discussed.     

Glyoxalase I activity inH-2 b andH-2 d cells

Erythrocytes and thymocytes of theH-2 ^d genotype express between 1.6 and 2.6 times as much glyoxalase I activity per milligram of protein as those of theH-2 ^b genotype; the activity in theF ₁ (H-2^b/H-2^d) cells is intermediate between these two values. Activity of glyoxalase II is not affected by the H-2 genotype. The H-2^d:H-2^b ratio of glyoxalase I activity is higher in the BALB background where it is 2.6:1 than in the B10 background where it is 1.6:1. Thermal denaturation kinetics of enzymes from the H-2^b and H-2^d genotype cells are the same.     

BALB/c-H-2 db : A newH-2 mutant in BALB/cKh that identifies a locus associated with theD region

A newH-2 mutant, BALB/c-H-2 ^db , is described. This mutant originated in BALB/c, is inbred, and is coisogenic with the parental BALB/cKh strain. The mutation is of the loss type since BALB/c-H- ^db rejects BALB/c, but not vice versa. Complementation studies have localized the mutation to theD region of theH-2 complex. A cross between BALB/c-H-2 ^db and B10.D2-H-2 ^da failed to complement for either BALB/c or B10.D2 skin grafts, indicating that these are two separate mutations at the same locus (Z2). Direct serological analysis and absorption studies revealed that, with one exception, theH-2 andIa specificities of BALB/c and BALB/c-H-2 ^db are identical. In particular,H-2.4, the H-2D^d private specificity, is quantitatively and qualitatively identical in the two strains. The exception is that of the specificities detected by antiserum D28b: (k×r)F₁ anti-h, which contains anti-H-2.27, 28, and 29. These specificities appear to be absent from theH-2 ^db mutant since they are not detected directly or by absorption. Other public specificities are present in normal amounts,e.g., the reaction with antisera to H-2.3, 8, 13, 35, and 36. The reaction with antiserum D28 (f×k)F₁ anti-s, which contains antibodies to H-2.28, 36, and 42, is the same in both strains. Antiserum made between the two strains (H-2 ^db anti-H-2 ^d ) reacts like an anti-H-2 serum, in that it reacts with both T and B cells by cytotoxicity, but is not a hemagglutinating antibody. The serum reacts as does the D28b serum in both strain distribution and in cross-absorption studies. We conclude that theH-2 ^db mutation occurred at a locus in theD region, resulting in the loss of the H-2.28 public serological specificity and of a histocompatibility antigen. Whether these are one and the same antigen is not yet known. The data, in view of other evidence, imply that the public and private specificities are coded for by separate genes.Abbreviations used in this paper are as follows CML cell-mediated lysis - MLR mixed lymphocyte reaction - GVHR graft-versus-host reaction - RFC rosette-forming cells - RAM-Ig rabbit anti-mouse IgG     

Eight new histocompatibility mutations associated with theH-2 complex

Eight newH-2 mutations are reported, five derived fromH-2 ^b and three fromH-2 ^d . TheH-2 ^b mutants (H-2 ^bg 3,H-2 ^bi ,H-2 ^bj ,H-2 ^bk , andH-2 ^bn ) were all of the gain+loss type, and all exceptH-2 ^bn were at the same locus asH-2 ^ba , associated with theK end. In addition,H-2 ^bg3 was histocompatible with previously reported mutationsH-2 ^bg1 andH-2 ^bg2. The MST for mutant grafts on normal hosts was 2 to 5 weeks. TheH-2 ^d mutations consisted of two losses (H-2 ^db ,H-2 ^bc and one gain + loss (H-2 ^dd ). They involved at least two, possibly three, loci and have MSTs of less than two weeks. All mutations were recovered in (C57BL/6Kh x BALB/cKh)F₁ hybrids, exceptH-2 ^db , which was isolated on a pure BALB/c background.     

H-2 antigen variants in a cultured mouse leukemia cell line

We have investigated the effect of immune selection against a single gene product on a cultured mouse Friend leukemia cell line. The clonal cell line used is heterozygous at theH-2 complex and expresses theH-2 ^d andH-2 ^b haplotypes. The genes selected against were theH-2K locus alleles. Variants were obtained after a single-step selection using either antiH-2K^b or anti-H-2K^d serum. The phenotypes of the variants obtained showed an interesting asymmetry between the two haplotypes. Selection against theH 2K ^b allele resulted in the isolation of the two expected types of variant-those that had lost only H-2K^b and those that had lost both H-2K^b and the linked H-2D^b. Selection against H-2K^d yielded, exclusively, variants that had lost both the selected antigen and the linked H-2D^d. None of the variants showed an alteration in expression of antigens intrans configuration. Karyotypic analyses of the variants revealed that all the cells had retained both copies of chromosome 17 present in the wild-type cells. The results suggest that the variants did not emerge through chromosome loss.     

Immune response to the H-X antigen on P815-X2

In a preceding report, the detection of an H-2-linked immune response to the H-X ^d antigen on the P815-X2 mastocytoma was demonstrated by the significantly increased survival of (C57BL/6 × DBA/2)F₁ (B6D2F1) male hybrids (H-X ^b ) compared with female siblings (H-X ^{b/H-X d} ) after injection with the histocompatible tumor (H-X ^d ). This interpretation was supported by the absence of this sex effect in reciprocal D2B6F1 hybrids (H-X ^d and H-X ^{d/H-X b} ). Additional findings presented in this paper support the conclusion that this sex effect is due to a true immunological response to H-X ^d : (a) Reciprocal (DBA/2 × C57BL/6 H-2 mutant)F₁ hybrids, as well as D2B6F1, failed to exhibit the sex effect: (b) the demonstration of the sex effect in (BALB/c × DBA/2)F₁ and (BALB/c-H-2 ^dm2 × DBA/2)F₁ hybrids and in (C57BL/10 × DBA/2)F₁ hybrids was consistent with the known H-X incompatibilities between the strains BALB/c and DBA/2 and C57BL/10 and DBA/2, respectively, previously demonstrated by skin grafting; and (c) the sex effect was not abrogated by castration of male B6D2F1 hybrids. Variability in the presence or absence of the sex effect was observed in various [recombinant inbred (RI) × DBA/2]F₁ hybrids and may be attributed to the influence of a regulatory non-H-2 gene which is closely linked to the gene coding for mouse kidney-androgen-regulated protein (KAP) but androgen-independent, or to variability in inheritance of the H-X ^b allele among the RI lines. It is proposed that the P815-X2 model may be utilized to type RI lines derived from a cross between C57BL/6 and DBA/2 for their H-X genotypes.Abbreviations B C57BL/6 origin allele - B6 C57BL/6 - B10 C57BL/10 - B6D2F1 (C57BL/6 × DBA/2)F₁ - B6 ^m D2F1 (C57BL/6 H-2 mutant × DBA/2)F₁ - bm10 B6.C-H-2 ^bm10 - C BALB/c - D DBA/2 origin allele - D2 DBA/2 - dm2 BALB/c-H-2 ^dm2 - H-X X chromosome-determined histocompatibility antigen of the mouse - Ir gene, immune response gene - KAP kidney androgenregulated protein - MST median survival time - RI recombinant inbred - SDP strain distribution pattern     

Murine responses to (Tyr-Glu-Ala-Gly)n: II. H-2 and non-H-2 gene effects

Mice of the H-2^b haplotype responded to the sequential polymer poly(Tyr-Glu-Ala-Gly) in the in vitro T-cell proliferative assay, irrespective of whether they were homozygous or heterozygous at the H-2^b locus. The antibody responses of the H-2^b congenic mice to this polymer were variable, with A.BY and BALB.B showing responses better than those of C57BL/6 and C57BL/10 strains. The antibody responses of the F₁ progeny of (responder × nonresponder) strains of mice to this polymer are generally lower than the responder parents. F₁ mice with C57BL/10 background were the poorest responders. Studies with F₂ mice and backcross progenies of selective breeding of high and low antibody responder (C57BL/6 × BALB/c) F₁ to high responder C57BL/6 mice indicated that both non-H-2 genes and H-2 gene dosage effects influenced the magnitude of the humoral antibody responses. Animals having low responder non-H-2 background and only half the dosage of the responder immune response genes has greatly diminished antibody responses.     

Further evidence that BALB/c and C57BL/6 gamma 2a genes originate from two distinct isotypes.

Gene conversion by the corresponding gamma 2b gene has been proposed to explain the multiple differences between the nucleic acid sequences of BALB/c (Igh-1a) and C57BL/6 (Igh-1b) gamma 2a immunoglobulin allelic genes. However, genetic analysis indicates that duplicated forms of gamma 2a genes are not only present in Eastern Asia, but also in European wild mouse populations which suggests a widespread phenomenon. In order to verify whether the gamma 2a-related isotypic genes, namely gamma 2c and gamma 2a, could correspond to those present as alleles in domestic mice (Igh-1b and Igh-1a), a genomic library from Mus m.musculus strain (MAI) was constructed. Extensive mapping of the recombinant phages and Southern blot analysis with several restriction enzymes gave the complete organization of these loci: gamma 2b (18 kb) gamma 2c (17 kb) gamma 2a (14 kb) epsilon. The homology in flanking, coding and intervening region sequences indicates that MAI gamma 2c and gamma 2a related genes correspond to C57BL/6 and BALB/c Igh-1 alleles respectively. Also, Southern blot analysis using several probes derived from exonic and intronic regions between gamma 2b and gamma 2a genes shows a 2.0- to 3.0-kb difference in the distance between gamma 2b and gamma 2a genes of BALB/c strain as compared to C57BL/6. Taken together, these results indicate that BALB/c and C57BL/6 gamma 2a genes could originate from different isotypes.     

H-2 antigen variants in a cultured heterozygous mouse leukemia cell line

In previous studies on the emergence of H-2 antigen loss variants from an H-2^b/H-2^d heterozygous mouse leukemia cell line, it has been shown that stable variants could be obtained after a single-step selection procedure with antibody and complement. Selection against the K-end alleles revealed an asymmetry in the types of variant obtained. This paper deals with the results of selection against theD-end alleles. Once again, an asymmetry is noticed. Selection against the H-2D^d gene product results in the isolation of stable variants that have lost H-2D^d, either alone or in combination with the linked H-2K^d antigens. Selection against H-2D^b, on the other hand, has not, so far, resulted in the isolation of any stable variants. These experiments have not demonstrated unequivocally the mechanism by which these H-2 antigen loss variants are generated. However, certain preliminary considerations suggest the possibility that these variants may not, in fact, be true genetic mutants. The alternative -that these variants arose through some nongenetic, but stable mechanism — must be considered seriously.     

Time course study of H-2 and other antigen expression by hybrids of a myeloma cell line with inflammatory macrophages

The hybrids (the CANS lines) between inflammatory macrophages from C57BL/6N (B6) mice (H-2^b) and BALB/c mouse (H-2^d)-derived myeloma cell line NS1 in the early period after cell fusion showed no macrophage functions. However, most of the hybrids expressed these functions after prolonged cultivation accompanied with chromosome loss. In contrast, the hybrids initially displaying myeloma functions ( light chain production) lost this function when they exhibited macrophage functions. We studied the expression of cell-surface antigens in these hybrids and found that hybrids in the early period after cell fusion codominantly expressed both parental cell H-2 antigens (H-2K^b, H-2K^d, and H-2D^d) but not the H-2D^b antigen. On the other hand, aged hybrids strongly expressed the H-2 d antigen but lacked the H-2K^b antigen. Alternatively, these aged hybrids with macrophage functions expressed antigen(s) as detected with antiaged CANS-196 cell sera and asialo GM1 antigen, both of which were thought to be found exclusively on macrophages. Thus, the expression of cell-surface antigens in these hybrids was greatly altered after cell fusion.     

Biochemical evidence for structurally distinct H-2Dd antigens differing in serological properties

H-2D^d antigens, as defined by the private H-2.4 determinant, exist as two immunochemically distinct populations in H-2^a and H-2^dm2 splenocytes and in the transformed cell line, RADA1(H-2 ^a). The two populations are distinguishable by the anti-H-2.28 serum, k/r anti-h2, which is directed, in part, against the H-2.28 family of public determinants encoded by the D end of the b haplotype. Sequential precipitates of lentil-lectin-purified glycoprotein extracts metabolically labeled with radioactive amino acids reveal that approximately one-quarter to one-third of the H-2D^d antigens, designated H-2D^d (b28 ⁺), react with this antiserum, whereas two-thirds to three-quarters, designated H-2D^d(b28^–), do not. Paired-label tryptic peptide maps in this and a previous study indicate that H-2D^d(b28⁺) and H-2D^d(b28 ^–) are closely related structurally and are more likely to represent modified forms of the same gene product rather than products of different genes, although the existence of closely related genetic loci is not rigorously excluded. Together, H-2D^d(b28⁺) and H-2D^d(b28^–) have a radioactivity level seven times higher than H-2L^d, which also reacts with the anti-H-2.28 serum but which lacks the H-2.4 determinant. As yet unresolved, however, is the question of whether the observed quantitative differences between these three antigens reflect actual molar differences at the cellular level, or whether the variation is the result of metabolic or compositional factors. In any case, a complex serological and structural relationship is found to exist between antigens encoded by the D/L end of the MHC.     

The regulation of immune responses to multiple non-H-2 antigens on tumor cells: I. Differential responses of BALB/c F1 hybrids to the P815 mastocytoma in vivo

Factors influencing host resistance to the growth of a tumor bearing many mismatched minor histocompatibility antigens (MiHA) were studied. BALB/c (H-2^d) and several of its F₁ hybrids were injected intraperitoneally with DBA/2 (H-2^d) P815 tumor cells. Compared to BALB/c, which was moderately susceptible, F₁ hybrids of BALB/c with CBA, AKR, C3H.OH, and BIO H-2-congenic strains were highly susceptible, whereas hybrids of BALB/ c with A, A.SW, and BALB.B strains were quite resistant. Susceptibility was observed only with the intraperitoneally injected tumor, since both BALB/c and (CBA x BALB/c)F₁ were resistant to the same tumor injected subcutaneously, and survival times of DBA/2 skin grafts did not differ between susceptible and resistant strains. Susceptibility was in part a function of the number of MiHA incompatibilities between tumor and host although the specific loci involved could not be identified. For example, susceptible (CBA x BALB/c)F₁ hybrids probably shared certain MiHA with DBA/2 which BALB/c lacked, and which therefore subtracted from the net antigenic strength of the tumor in the hybrid, compared to its strength in BALB/ c. This interpretation was supported by in vitro studies which confirmed that the susceptible hybrids shared more MiHA with DBA/2, than did the resistant hybrids. Resistance was at least partially regulated by the host H-2 genotype, as shown by the observation that (BALB/ c x BALB.B)F₁ (H-2^d/b) mice were significantly more resistant than BALB/c. Segregation studies of the resistant (BALB/c x A)F₁ hybrids, indicated that in addition to H-2, a nonH-2 gene in the A background was operating to confer resistance. Thus the factors influencing susceptibility to the MiHA-incompatible tumor were: (i) site of injection; (ii) the combined strength of the disparate MiHA; (iii) the host H-2 genotype; and (iv) at least one host nonH-2 gene conferring increased responsiveness.     

Synthesis of a defective H-2 histocompatibility antigen by mutant mouse strain BALB/c-H-2 dm2

Mutant mouse strain BALB/c-H-2 ^dm2 (dm2), which fails to express the H-2L^d histocompatibility antigen associated with the wild type, BALB/c, synthesizes instead a smaller molecule that is structurally related to H-2L^d but does not carry detectable alloantigenic determinants. This new protein, p40, is a membrane glycoprotein found in dm2 cells but not in BALB/c. p40 was detected by electrophoresis of dm2 glycoprotein preparations and by immunoprecipitation with heterologous H-2-specific antibodies. The p40 molecule is found associated with intracellular membranes but was not detected at the cell surface. Peptide mapping studies suggest that dm2 carries an alteration in the H-2L ^d structural gene, which prevents proper maturation of the protein product.     

Genetic control of contact sensitivity in mice: Effect ofH-2 and nonH-2 loci

The genetic control of delayed-type hypersensitivity in mice was investigated by contact sensitization with picryl chloride. Distribution patterns of contact sensitivity in 11 inbred strains of mice showed significant differences among strains. Comparison of levels of response between congenic-resistant lines and their inbred partners, at 9 to 11 weeks of age, revealed a clear association betweenH-2 haplotype and the magnitude of response. Testing ofH-2 recombinants further suggested the influence of two genes mapping at either end of theH-2 complex. While theH-2K ^d andH-2D ^k alleles were associated with a high response, theH-2K ^k ,H-2K ^b ,H-2D ^d , andH-2D ^b alleles were associated with a low response. Analysis of the ontogeny of response suggested that theH-2 haplotype manifests its effect through the maturation of contact sensitivity. On both the C57BL/6By and C57BL/10Sn backgrounds, theH-2 ^d haplotype was associated with early maturation of response, while theH-2 ^b haplotype was associated with late maturation. Analysis of the response of congenic lines with different genetic backgrounds and of CXB recombinant-inbred lines further revealed the marked effects of yet other genes on this trait.     

H-2 antigen expression: Loss in vitro,restoration in vivo,and correlation with cell-mediated cytotoxicity in a mouse lymphoma cell line

The susceptibility to cell-mediated cytolysis of cells of the recently developed C57BL/Ka(H-2 ^b ) lymphoma cell line, BL/VL₃, was investigated in allogeneic assays with thymus-dependent lymphocytes (T cells). Compared to EL4, the widely used C57BL/6(H-2 ^b ) lymphoma cell line, BL/VL₃ cells were found to be insensitive to T-cell-mediated lysis as detected by the use of⁵¹Crrelease methods. When used as immunogens in alloreactive combinations with BALB/c(H-2 ^d ) splenocytes as responder cells, BL/VL₃ cells failed to elicit sensitization. Serological tests showed that this cell line had profoundly reduced levels of H-2^b antigens on its surface. When BL/VL₃ cells were reinjected into C57BL/Ka and BALB/c mice, full recovery of H-2^b antigen expression at the cell surface was observed in both syngeneic and allogeneic hosts after only 11 days of in vivo growth. Concomitantly, they acquired the ability to induce cytotoxic responses in allogeneic T cells and became susceptible to their lytic activity. The expression of H-2 antigens on the surface of BL/VL₃ cells is a reversibly modulated function that depends on in vivo growth conditions and is lost in vitro in the absence of immunoselective pressure.     

Antigen-specific helper T cells recognize determinants encoded in the H-2D region of the H-2 gene complex

Observations have frequently been interpreted as showing that the helper T cells which collaborate with alloantigen-specific cytotoxic T-cell precursors can only recognize antigens encoded in the I region of the H-2 gene complex. An experimental system is described here that allows analysis of the recognition repertoire of these helper cells. CBA helper T-cell precursors can be primed in vitro to antigens encoded in the H-2 ^b gene complex. These helpers can then be tested for the existence of a subset of helper cells which recognize antigens encoded in the D region of H-2 ^b haplotype. CBA thymocytes were used as a source of cytotoxic T-cell precursors that respond poorly in the absence of exogeneous helper activity. The source of alloantigen was varied by using irradiated spleen cells from various (BALB/c × recombinant)F₁ hybrid mice as stimulator cells. When the stimulator cell bears BALB/c determinants recognized by the cytotoxic T-cell precursor and also bears only the D region antigens of the H-2 ^b haplotype, an anti-BALB/c cytotoxic response is generated only if the anti-H-2^b helper population contains cells able to recognize H-2D^b. A positive cytotoxic response was obtained, indicating that helper cells are not limited to recognition of I region antigens and can efficiently recognize antigens encoded in the D region of the H-2 gene complex. This was confirmed by the demonstration of helpers specific for H-2D^d. We were unable to detect any evidence for Ia-restricted recognition of the H-2D alloantigens, suggesting that, as for cytotoxic T lymphocytes (CTL), helper cell recognition of class I alloantigens is an unrestricted event.     

H-2 control of expression of an idiotype shared by normal B cells and a B-cell lymphoma

The spleens of normal B10,H-2 ^a H-44^b p/Wts (2 ^a 4 ^b ) mice; contain cells which, in response to mitogen stimulation, secrete hemolytic antibody specific for a determinant present on both sheep and bromelain-treated mouse erythrocytes. These cells were found to be Ly-1 positive. Approximately 50% of these cells bear surface immunoglobulin (sIg) with the same idiotype as the sIg of a 2^a4^b-derived B-cell lymphoma, CH12. Backcross analysis revealed H-2 control of the frequency of the idiotype-positive B cell. The regulatory gene did not correlate with the Igh-1 allotype, and analysis of 22 inbred mouse strains mapped the gene to the I-E subregion. Surprisingly, only strains homozygous for E ^k expressed the idiotype, and expression was a recessive trait. Possible mechanisms for this control of idiotype expression and its relation to lymphomagenesis are discussed.Abbreviations used in this paper 2 ^a4^b B10.H-2 ^aH-4^bp/Wts - Br-MRBC bromelain-treated mouse erythrocytes - C complement - LPS lipopolysaccharide W - pfc plaque-forming cells - sIg surface immunoglobulin - SRBC sheep erythrocytes - Ts T suppressor.