Ly-m11: the H-3 region of mouse chromosome 2 controls a new surface alloantigen

Complexity of minor histocompatibility loci

Allografts can be rejected as a result of major histocompatibility antigen disparity or as a result of differences at any of a number of minor histocompatibility antigens. In many cases, rejection due to multiple minor histoincompatibility is as difficult to control as that induced by major histoincompatibility. Although an understanding of the molecular, biochemical, and functional parameters of the major histocompatibility loci and their products is increasing at an exponential rate, little is known about these same facets of minor histocompatibility loci and their products. It is generally accepted that minor histocompatibility loci in the murine model have a degree of polymorphism similar to that of H-2K or H-2D. This conclusion was based on typing alleles by the classic F1-skin graft test. Based on these allelic assignments, numerous unexpected findings of CTL specificity were made. Therefore, a systematic analysis was made comparing CTL specificity, F1-complementation, and allograft rejection. Based on these three parameters, the data presented using strains of mice that were bred to, and therefore presumed to, differ only at H-3 indicate that the antigen disparity of these congenic strains and the parental B10 strain as defined by CTL specificity and skin graft rejection is much more complex than originally described. One especially interesting chromosomal region is H-3/beta 2-microglobulin in the fifth linkage group of chromosome 2. Using CTL, ten specificities are defined, three of which appear to be specific for beta 2-microglobulin-A, -B, and -C. These findings raise the question of whether any minor histocompatibility locus is polymorphic or is instead a composite of multiple minor H-loci which are masquerading as a single locus.

Retroviral insertional mutagenesis of a target allele in a heterozygous murine cell line

A clonal murine cell line that is heterozygous at the beta 2-microglobulin locus (B2m) was obtained by Abelson murine leukemia virus (Ab-MuLV) transformation of liver cells from (C57BL/6 X BALB/c) F1 fetuses. To obtain proviral insertional mutants, we superinfected a subclone of these cells, which does not express the env surface protein of the Moloney leukemia virus (Mo-MuLV, the helper virus that was used to transmit the defective Ab-MuLV genome during transformation), with Mo-MuLV. Mutant clones that fail to express the C57BL/6 allele of B2m (B2mb) were then immunoselected by using a monoclonal antibody that specifically recognizes the B2mb gene product and not that of the B2ma allele. Of 22 independent clones obtained, one contains a proviral insertion that is near or in the first exon of the B2mb gene. Surprisingly, the insertion is of the Ab-MuLV genome and not of replication-competent Mo-MuLV. This indicates that superinfection with Mo-MuLV "rescued" the defective Ab-MuLV genome, which then inserted into the B2mb gene. We conclude that when an allele-specific selection procedure exists, proviral insertion is a potential method for obtaining mutations in heterozygous mammalian cells. This approach may thereby provide a method for molecular cloning of such selectable genes, using a retroviral hybridization probe.

Histidine decarboxylase phenotypes of inbred mouse strains: a regulatory locus (Hdc) determines kidney enzyme concentration

Mouse kidney histidine decarboxylase (HDC) provides a model system to study genetic control of a hormone-regulated enzyme (inducible by estrogen and thyroxine; repressible by testosterone). Five major HDC phenotypes scored on the basis of (i) enzyme activity and (ii) the difference in activity between the sexes (females usually higher than males) have been discovered by screening 38 strains of mice. One genetic difference between high-activity strains (DBA/2 and C3H/He) and low-activity strains (C57BL/6 and C57BL/10) has been examined in detail. The phenotypic difference segregates as a single gene in both conventional crosses and between recombinant inbred (RI) strains. Immunoprecipitation has shown that the activity difference is due to an alteration in the number of enzyme molecules. The phenotypic difference between high and low strains can therefore be attributed to different alleles of a single regulatory locus, Hdc; the allele Hdcb determines low HDC concentration, and the allele Hdcd high concentration. Hdc has been mapped to chromosome 2 using data from both comparisons of strain distribution patterns of previously mapped loci within RI strains and a conventional three-point cross. The probable gene order is B2m-pa-Hdc, with map distances of 3.1 +/- 1.7 and 2.0 +/- 1.4 cM, respectively.

Interaction between MHC-encoded products and cloned T cells. II. Analyses of physiological requirements indicate two different pathways of stimulation by class I alloantigens

The interaction between class I major histocompatibility complex (MHC) products and T cells was studied using H-2Kb-specific alloreactive T-cell lines and clones obtained by repeated in vitro stimulation with allogeneic cells. Induction of proliferation of these T cells appeared to involve two signals: the H-2Kb alloantigen and interleukins. Immunopurified liposome-inserted H-2Kb, which stimulates specific secondary in vitro cytotoxic T lymphocyte (CTL) responses, could not replace cell-associated H-2Kb in the stimulation of these T-cell lines, even in the presence of feeder cells and interleukins. When T-cell lines were initiated in vitro and repeatedly stimulated with H-2Kb liposomes and feeder cells, it was possible to obtain T cells that could proliferate in response to H-2Kb liposomes in the presence of feeder cells and interleukin-2-containing supernatants or on H-2Kb-expressing cells. Only stimulation with cells permitted maintenance of these T cells in culture for more than 12 weeks. Analyses of cell surface markers and of patterns of inhibition of proliferation by monoclonal antibodies (mAb) of T-cell lines induced in vitro with cell- or liposome-associated H-2Kb indicated that T-cell stimulation by class I antigen can occur in at least two ways. In the first, the H-2Kb-induced proliferation of Lyt-1- Lyt-2+ T4- T cells is inhibited by H-2Kb- and by Lyt-2-specific mAb, but not by Ia or T4-specific mAb. In the second, both Lyt-2+ and T4+ T cells are involved and the H-2Kb-induced proliferation is inhibited by H-2Kb- and Lyt-2-specific mAb and by Ia- and T4-specific mAb.

Beta-2 microglobulin types in mice of wild origin

To determine the distribution of beta-2 microglobulin (B2m) alleles in wild mice we have typed mice derived from natural populations in Europe, North Africa, South America, and East Asia. Mus musculus domesticus mice from Germany, France, Italy, and Peru were all B2ma as were most from the United Kingdom. M.m. musculus mice from Denmark and Czechoslovakia, several stocks of M.m. molossinus from Japan, and M.m. castaneus from China, Thailand, and the Philippines were of B2mb type. This is consistent with the notion that C57BL/6 may have obtained some of its genes, including B2m, from Eastern mice. A BglI restriction site characteristic of B2mb was also found in mice from Czechoslovakia and Japan, confirming that B2mb is a naturally occurring allele of B2m. A new type of beta 2m (beta 2mwl) was found in four stocks of M. spretus from Portugal, Spain, and Morocco. This molecule differs in apparent size and charge from the a and b types. Beta 2mw2 was found together with beta 2ma in one stock of M.m. domesticus (brevirostris) from Morocco. Beta 2mw3 and beta 2mw4 were found in a few M.m. bactrianus from Pakistan. In all cases tested, these new beta 2m molecules associate with class I histocompatibility antigens.

Selective reversal of H-2 linked genetic unresponsiveness to lysozymes. I. Non-H-2 gene(s) closely linked to the Ir-2 locus on chromosome 2 permit(s) an antilysozyme response in H-2b mice

Genes outside of the mouse major histocompatibility complex (H-2) were found to be capable of specifically reversing the previously described nonresponsiveness to hen egg-white lysozyme (HEL) owing to H-2b immune response (Ir) genes. C3H.SW, BALB.B, and C57L, all of the H-2b haplotype, showed responsiveness to HEL, but not to human lysozyme (HUL). Mapping of the reversing gene(s) was attempted by testing H-2b recombinant inbred (RI) strains of mice carrying C3H, BALB, and C57L non-H-2 genes. Analysis of the strain distribution pattern of responsiveness with both CXB and BXH RI strains was consistent with the location of the responsible site within the H-3 region on chromosome 2. The anti-HEL proliferative responsiveness in two H-3 congenic strains of mice, B10.C(28NX)SN and B10.C-H-3cH-3a, that have BALB/c genes within the H-3 region confirmed the mapping, as well as localized the reversing gene(s) near the Ir-2 gene. The data are discussed with regard to the site of expression of the reversing gene(s) and its mechanism of action.

A new H-2-linked class I gene whose expression depends on a maternally inherited factor

The maternally transmitted antigen (Mta) is expressed on the cells of most strains of mice. It is a medial histocompatibility antigen, that is, it is recognized by unrestricted cytotoxic T lymphocytes as are major H antigens, but unlike these it is a weak transplantation antigen and does not itself restrict the T-cell recognition of minor H antigens. All other medial H antigens are encoded by genes closely linked to the major histocompatibility complex, H-2 in the mouse. By contrast, Mta appeared to follow extrachromosomal, maternal inheritance. Several substrains of NZB, NZO and non-inbred European NMRI mice are Mta-negative. Females of these strains bear only Mta- offspring, while females of the inbred Mta+ strains bear only Mta+ offspring. Repeated backcrossing from Mta+ females to NZB or NMRI males has shown that, given the right cytoplasmic genes, the chromosomal genes of these Mta- strains permit expression of Mta2. As the Mta type of a mouse cannot be influenced by embryo transfer or foster nursing, we concluded that it was determined by a cytoplasmic factor (Mtf), transmitted through the egg. We now show that a gene, Hmt, closely linked to the H-2 complex, is also required for expression of Mta.

A lymphocyte antigen encoded by a locus closely linked to H-3 on the second chromosome of the mouse

A monoclonal antibody has been developed that recognizes a mouse lymphocyte antigen, Ly-23, that is controlled by an H-3 histocompatibility complex-linked gene on the second chromosome. Competitive binding experiments demonstrate that this antigen is distinct from the polymorphic beta 2-microglobulin antigen, which also is encoded by a gene closely linked to H-3. The strain distribution pattern differs from that of the beta 2-microglobulin polymorphism, and recombination apparently has separated the genes for these two antigens during the derivation of one recombinant inbred line. However, the R1E/TL8X line of cells, which lacks beta 2-microglobulin, is negative for the Ly-23 antigen, although the control R1.1 line is positive. The H-2 locus affects the expression of both the Ly-23 and beta 2-microglobulin antigens.

Linkage of beta 2-microglobulin and ly-m11 by molecular cloning and DNA-mediated gene transfer

beta 2-Microglobulin (beta 2m) is expressed on the cell surface after introduction of a beta 2mb (C57BL/6N) genomic clone into thymidine kinase-deficient mouse L cells by cotransformation using the calcium phosphate precipitate method. Stable transformant cell lines were identified that express the beta 2mb allele, as determined by reaction of the cells with appropriate monoclonal antibodies and by two-dimensional gel electrophoresis of endogenously labeled immunoprecipitates of cell extracts. These beta 2mb transformants now express ly-m11.2, as detected by an indirect radioimmunoassay. A plasmid subclone of the beta 2mb gene that contains an 8.4-kilobase insert, after introduction into mouse L cells, similarly directs the synthesis of both the beta 2mb and the ly-m11.2 antigens. Thus, the beta 2mb and ly-m11.2 determinants most likely represent sites on the same protein structure.

Mouse alloantigen system Ly-m22 predominantly expressed on T lymphocytes and controlled by a gene linked to M1s region on chromosome 1

Spleen cells from a DBA/2 mouse immunized with RL male 1 tumor cells, a radiation induced BALB/c T-cell leukemia, were hybridized with the nonsecretor myeloma line NS.1. Four established hybrid cell lines continuously secreted antibodies that recognized a new alloantigenic specificity, tentatively called Ly-m22. This antigen is detectable on nearly 60% of lymph node cells, and 30% of spleen cells by direct cytotoxicity assay, but did not lyse significant number of cells of thymus and bone marrow. By absorption test, these lymphoid organs, i.e., lymph node, spleen, thymus, and bone marrow, were shown to express Ly-m22 determinant. The newly found antigen is expressed predominantly on T-cells. Analysis of BXD and SWXL recombinant inbred strains revealed close linkage between Ly-m22 and Ltw-4 loci on chromosome 1. The estimated recombination frequency is 0.027 +/- 0.081.

Evidence for a major cluster of lymphocyte differentiation antigens on murine chromosome 2

The region of chromosome 2 between H-13 and H-3 has been shown to contain loci coding for a variety of other alloantigens, including Ly-4 and the locus coding for beta 2-microglobulin. Herein we show that Ly-6 and Ly-11 are coded for by genes in a segment of chromosome 2 adjacent to the H-3-H-13 region and that this segment of chromosome also contains the tightly linked loci coding for antigens Ala-1, DAG, H9/25, H-30, Ly-8, and ThB. In addition, at least one locus (and probably more) affecting susceptibility to leukemia induction is found within this gene cluster.

Genetic characterization of a polymorphic murine cell-surface glycoprotein

As described in the preceding paper, monoclonal antibodies have been raised by immunization of rats with mouse hematopoietic cells which detect a major cell-surface glycoprotein (Mr = 95 000) of mouse bone-marrow cells of the granulocytic series. While most of the monoclonal antibodies detect this molecule one bone-marrow and spleen cells of all mouse strains, two antibodies recognize alternative allelic forms of the molecule. One alloantigen is expressed in all the remaining inbred strains examined. The alloantigens are codominantly expressed on the cells of F1 mice. Backcrosses of DBA/2 and C57BL/6 with F1 mice (B6D2F1) confirmed that a single genetic locus is involved in the expression of the two antigenic forms and demonstrated linkage to Ly-m11 which has previously been mapped to mouse chromosome 2. These genetic mapping experiments and the biochemical properties of the glycoprotein suggested that it might be identical to a glycoprotein first identified on murine fibroblasts by Hughes and August and designated Pgp-1. This has been firmly established by exchange of monoclonal antibody reagents and sequential immunoprecipitations.

A new murine lymphocyte alloantigen, Ly-21.2, mapping to the seventh chromosome

Using a monoclonal antibody raised by fusing spleen cells from A/J mice, immunized with B10.A splenocytes and lymph-node cells, with a BALB/c myeloma, we have described a new surface alloantigen, Ly-21.2, Ly-21.2 is present in varying amounts in all lymphoid tissues, is not detectable in the brain, kidney, lung or erythrocytes, and is found in only trace amounts in the liver. Strain distribution studies showed that Ly-21.2 is present in all strains examined, including B10, except the A strain and segregation analysis of (A/J x B10) F2 mice showed that Ly-21.2 expression (1) is encoded by one gene and (2) is linked to albinism on chromosome 7. Studies performed on mice developing T-cell leukemia showed that, regardless of the etiologic agent, Ly-21.2 expression increases dramatically in mice with overt leukemia. In addition, preliminary studies suggest that expression of Ly-21.2 is linked to increased susceptibility of mice to Friend-virus-induced erythroleukemia.

Gene for a major cell surface glycoprotein of mouse macrophages and other phagocytic cells is on chromosome 2

A gene controlling the expression of a polymorphic 92,000-dalton glycoprotein of mouse macrophages and granulocytes has been identified. This glycoprotein was previously shown to be the major iodinated, trypsin-sensitive component of the murine phagocyte cell surface. The gene has been provisionally designated Pgp-1 for phagocyte glycoprotein 1. Expression of the glycoprotein was measured by monoclonal antibody binding to a polymorphic antigenic determinant. Antibody binding to cells of positive strains of mice was proportional to cell number, whereas binding to cells of negative strains was insignificant. The concentration of the antigen in cells of heterozygous mice was approximately 50% of that in homozygous mice. Thirteen of 33 recombinant inbred strains of mice were positive, with binding values 100-fold over background, suggesting that a single gene controlled expression of the antigen. Segregation of the antigen correlated with markers on chromosome 2. The segregation of Pgp-1, with nonagouti coat color (a) and hemolytic complement (Hc) activity among progeny of (C3H/HeJ x DBA/2J)F1 x DBA/2J mice confirmed the single gene control and the chromosomal assignment. Another gene on chromosome 2, Ly-m11, was also typed by using (BALB/cJ x C57BL/6J)F1 x C57BL/6J mice. The data from both of these crosses indicated the following gene order: Hc--Pgp-1--Ly-m11--a.

Genetic analysis of the non-H-2-linked Ir genes controlling the cytotoxic T-cell response to H-Y in H-2d mice

The T-cell mediated immune responses to the male specific minor histocompatibility antigen H-Y in mice have been studied extensively as a model for immune responses to other weak antigens like tumor antigens or autoantigens. In a recent analysis of the strain distribution of the cytotoxic T-cell (Tc-cell) responsiveness to H-Y, it has been found that genes both within and outside the H-2 complex exert an interactive control. Whereas the H-2b strains all are high responders, independent of their non-H-2 background, other H-2 haplotypes (d, k, and s) only allow for a response if they are combined with certain non-H-2 genes. The H-2-linked immune response genes (Ir-genes) have been previously mapped to the I and K or D region of the H-2 complex, but the mapping of the non-H-2 genes has not yet been established. In this study evidence is presented, using recombinant inbred strains and immunoglobulin heavy chain (Igh) congenic strains of mice, to show that there is more than one non-H-2 Ir-gene involved, that the main controlling genes are not linked to the Igh complex, and that at least one non-H-2 Ir-gene is linked to the H-3 region on chromosome 2. This region includes genes for beta-2-microglobulin (beta 2m), the Ly-m11 alloantigen a polymorphic cell surface glycoprotein (Pgp-1), a B-cell specific antigen Ly-4, a transplantation antigen H-3, and genes (Ir-2) controlling the immune response to Ea-1 and H-13.

A new mouse cell-surface antigen (Ly-m18) defined by a monoclonal antibody

Spleen cells from C3H/An mice immunized with spleen cells of C57BL/6-H-2k mice were fused with myeloma cell line NS.1. One established hybrid cell line continuously secreted antibody that recognized a new surface antigen provisionally called Ly-m18. The new alloantigen is expressed on 90 percent of thymus cells, 55 percent of spleen cells, and 45 percent of either lymph-node or bone-marrow cells. It is also expressed on cells derived from brain, kidney, and liver. Fifty percent of either peripheral T or B cells express the Ly-m18 antigen, and some tumor cell lines with T, B, pre-B or stem cell characteristics are Ly-m18 (+). The strain distribution pattern distinguishes Ly-m18 antigen from all other murine lymphocyte alloantigens. The typing data of two sets of CXB and AKXL recombinant inbred strains indicate that the Ly-m18 gene is linked to the Ltw-2 locus which has not yet been assigned to a chromosome.

A new mouse cell-surface antigen (Ly-m20) controlled by a gene linked to Mls locus and defined by monoclonal antibodies

Five monoclonal antibodies were established by the fusion of mouse myeloma cells (NS.1) with spleen cells from A and (A x C3H/An)F1 mice hyperimmunized with 70Z/3 tumor cells. These antibodies recognized a new antigenic specificity provisionally called Ly-m20.2. In direct cytotoxicity assays, 60 percent of cells in spleen, 40 percent in lymph node, 50 percent in bone marrow and less than 5 percent in thymus were found to react with three of the five antibodies, whereas the two others yielded somewhat lower cytotoxicity indices. The Ly-m20.2 antigen was also expressed on cells derived from liver and kidney but not on cells derived from brain. As judged from cytotoxicity assays with separated T and B cells, Ly-m20.2 antigen is carried preferentially on B lymphocytes. Direct plaque-forming cells (PFC) were completely eliminated by Ly-m20.2-specific antibody and complement. Linkage tests by analysis in 20 (CBA/J x C3H/An) x C3H/An backcross mice and by segregation analysis of BXH and SWXL recombinant inbred strains indicate close association of the loci controlling Ly-m20.2 and M1s antigens on chromosome 1.

Ly-m19: the Lyb-2 region of mouse chromosome 4 controls a new surface alloantigen

Spleen cells from an SJL mouse immunized with 70Z/3 cells, an established pre-B cell line, were fused with cells of the nonsecretory myeloma line NS.1. One established hybridoma cell line (clone K10.6) continuously secreted antibody that recognized a new antigenic specificity tentatively named Ly-m19. This newly found antigen is detectable on both T and B cells. Cytotoxicity assays reveal that 75 percent of the spleen and lymph-node cells, 35 percent of bone-marrow cells, and 15 percent of thymus cells reacted with antibody of clone K10.6. Strains expressing the specificity Ly-m19.1 are characterized by negative reactions and include the strains AKR, CE/J, RF/J, GR/A, SJL, P/J, BDP/J, and LG/J. All other strains so far tested are Ly-m19.2. This strain distribution pattern distinguishes Ly-m19 from any known murine lymphocyte alloantigen, but it parallels the Lyb-2c haplotype. Linkage test of a set of AKXL recombinant inbred strains revealed close linkage of Ly-m19 and Lyb-2 loci on mouse chromosome 4.

New mouse immunoglobulin A heavy chain allotype specificities detected using the hybridoma-derived IgA of I/St mice

Immunizations of C57BL/6 and A mice with IgA derived from the I/St mouse strain yield alloantisera which detect two allotypic determinants of immunoglobulin A. The two determinants display discrete strain distributions. The first, identified by the alloantiserum C57BL/6 anti-IgA of I/St strain hybridoma ID150, follows the Ighc haplotype, and the second, identified by the alloantiserum A anti-IgA of I/St strain hybridoma ID150, correlates with Ighc and Ighb haplotypes. Absorption with monoclonal IgM, which has the same idiotype as the ID150 IgA clone, removed idiotype-specific antibodies from both alloantisera. The remaining antibodies are directed against determinants associated with the alpha chain constant region, as shown by absorption with monoclonal IgA. By use of recombinant inbred strains of mice and mice congenic at the Igh locus, the loci controlling both C alpha allotypic determinants have been mapped to the Igh region on chromosome 12.