Class-II HLA restriction of antigen-specific human T-lymphocyte clones. Evidence of restriction elements on both DR and MT molecules.

Blast-enriched suspensions of T cells primed for Chlamydia trachomatis antigen were cloned by a limiting dilution technique. The class-II HLA restriction of T-lymphocyte clones (TLC) was studied by using allogeneic antigen-presenting cells (APC) carrying foreign class-II HLA antigens. Most of the TLC were restricted by one or the other of the D/DR determinants of the T-cell donor; that is, they did not respond when antigen was presented by APC expressing foreign D/DR determinants. Furthermore, heterogeneity of the DR4-expressing molecule could be demonstrated by T-cell clones from one person; APC from family members expressing DR4 gave high proliferative responses, whereas no proliferation was observed with most APC from unrelated persons expressing DR4. This heterogeneity of DR4 was confirmed by mixed lymphocyte culture (MLC) experiments, indicating a close relationship between restriction epitopes and those that activate allogeneic T cells. Other clones seemed to be restricted by other class-II HLA determinants, most probably MT determinants of the T-cell donor. The restriction specificities were confirmed by subcloning experiments.