CELLULAR AND BIOCHEMICAL STUDIES OF CLASS II MOLECULES ENCODED BY THE HLA-D REGION OF THE HUMAN MAJOR HISTOCOMPATIBILITY COMPLEX

The underlying theme of this thesis has emphasized the need to define all HLA-class II molecules that are expressed, and to evaluate their function as regards T lymphocyte responses, in order to gain a sound understanding of the MHC immunogenetic system. The particular areas of interest pursued were restricted recognition of foreign antigen by T lymphocytes and the identification of additional class II molecules.;Protein studies involved the identification of an unknown class II molecule (FA) as the DP molecule. The FA molecule was known to be different from DR and DQ, however its relationship to the DP molecule was not known. Experiments were done comparing DP phenotypes, as defined by T lymphocytes, with isoelectric focusing patterns of FA molecules. In almost every case a complete correlation was found. Also, A DR-/DQ-null mutant LCL, which expresses only the DP molecule, was used as a source of the FA molecule in preclearing and 2-dimensional gel studies which compared the FA molecule with the DP molecule was precipitated by an anti-DP mAb.;Additional protein studies resulted in the discovery of a new class II molecule which is different from DR, DQ and DP molecules. This new alpha/beta dimer is precipitated by an anti-DQ mAb from a LCL extract from which the DR and DP molecules had been removed. In addition, a new beta chain is precipitated by an anti-DQ mAb and another mAb, which has broad cross-reactivity with all class II molecules, from a mutant LCL which had lost expression of both DR and DQ molecules due to deletions of their respective genes.;In the area of restricted recognition of foreign antigen by T lymphocytes, two questions were asked: (1) are the restricting determinants (RDs) for T cell recognition of cytomegalovirus (CMV) different from serologically-defined allodeterminants and (2) on which class II molecules are these RDs located. It was found that CMV-specific RDs were not identical to serologically-defined allodeterminants, but were more closely related to T lymphocyte-defined allodeterminants. In addition, both DR and DQ molecules expressed these RDs.