Studies of Class I Genes in the Major Histocompatibility Complex of the BALB/c Mouse

This thesis contains the results of investigations into the structure and organization of Class I genes in the major histocompatibility complex of the BALB/c mouse. In the body of the thesis, the sequence of the BALB/c H-2Dd transplantation antigen gene is presented. This is the first complete sequence of an H-2Dd gene and is the only genomic sequence to be in full agreement with the available protein sequence. The H-2Dd gene sequence has been used to predict the protein sequence of the H-2Dd molecule, which has been compared to the protein sequences of other Class I molecules. The H-2Dd protein sequence is no more related to that of its closely linked partner, H-2Ld, than it is to the sequence of its presumptive allele, H-2Db, or to the sequence of the H-2Kb molecule, which is from not only another H-2 haplotype but another genetic subregion. The sequence differences between these transplantation antigens are spread throughout the molecules in a mosaic pattern that may have arisen,in part, from small gene conversion events. No obvious evidence of any recent gene conversion event affecting the H-2Dd gene was observed, however. Three Class I genes have been cloned and mapped to the H-2D subregion in BALB/c. These include gene 16.1, whose product has not been identified; the H-2Dd gene; and the H-2Ld gene. There is serological evidence for the existence of additional H-2D-encoded transplantation antigen molecules in BALB/c, but no genes encoding these products have been identified. The sequence of the H-2Dd gene contains potential alternative splice sites in and around the exon encoding the first external domain. use of these splice sites could generate a transplantation antigen molecule with different serological determinants, and might help to resolve the discrepancy between the number of H-2D-subregion Class I genes and the number of serologically defined H-2D-subregion transplantation antigens. The appendices contain the results of a number of studies related to Class I gene organization and function. Appendix A contains the sequence of gene 27.1. This gene, also known as the Q8 gene, was identified as a Qa pseudogene based on the presence of termination codons in inappropriate locations in its sequence. Appendix B contains the sequence of the H-2Ld gene, which was the first transplantation antigen gene to be sequenced. Appendix C contains the results of DNA-mediated gene transfer experiments that Identified genomic clones containing the H-2Kd, H-2Ld, and H-2Dd transplantation antigen genes as well as Class I genes encoding the Qa2,3 molecule and two different TL differentiation antigen genes. Appendix D contains the results of calculations of protein sequence homology between different Class I molecules.