Hemopoietic Histocompatibility (Hh-1) Antigens: Polymorphism and Mapping
“Hybrid resistance” to grafts of parental strain bone marrow cells (BMC) by irradiated H-2 heterozygous Fl hybrid mice suggested that Hh-1 antigens were inherited recessively. H-2 homozygosity is required for optimal immunogenicity of BMC grafts. H-2 b /H-2 d lymphoma cells are Hh-1 null but variants which do not express H-2D d do express Hh-1 b . This suggests that trans-acting genes at or near H-2D down-regulate the expression of Hh-1 antigens. NK cells mediate BMC graft rejection and immune response-like genes control the ability to reject BMC grafts in an Hh-1 determinant-specific manner. We have used a panel of recipient mice which reject certain strain BMC grafts in order to determine the Hh-1 phenotype of new strains of mice to be tested. When non-recombinant H-2 types of independent origin were studied, six patterns of expression of four different Hh-1 determinants were detected. The extremely limited degree of polymorphism compared to H-2 is interesting because NK cells do not rearrange immunoglobulin or T cell receptor genes and are expected to possess a paucity of receptor diversity. The great majority of more than 60 intra-H-2 recombinant strain mice had Hh-1 alleles predicted by H-2D or L. However, of the many H-2S/D recombinants, two strains expressed Hh-1 alleles which did not correlate with L. A unique D d /L b recombinant, B10.RQDB, expresses the Hh-1 phenotype which is characteristic of the d haplotype, indicating that Hh-1 maps to the left of H-2L. Since the Lb is the only b haplotype class I molecule at H-2DL, Hh-1 b cannot be a class I gene. In another strain, H-2S is predictive of Hh-1. Even more interesting are several strains which express Hh-1 phenotypes different from both donor strains which generated the recombinant. We believe that these strains represent intra-Hh-1 recombinants; furthermore, intra- Hh-1 crossover events are not rare. Recombinants involving H-2 f indicate that the structural genes for Hh-1 f are linked to H-2 and appear to map to the left of the regulatory genes (possibly centromeric of E β ). Other intra-Hh-1 recombinants indicate that the structural genes of most haplotypes map just to the left of the regulatory genes in the S/D interval of H-2.
KeywordsDonor Strain Hybrid Resistance Null Phenotype Cell Receptor Gene Regulatory Genotype
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