HLA-D: The T Cell Perspective

The introduction of the mixed leukocyte culture test MLC combined with the establishment of a one-way method of stimulation in MLC allowed the correlation of proliferative response in MLC with results of serological studies and the suggestion that reactivity in MLC is controlled by the major histocompatibility complex in man, now known as HLA. That the chromosomal region of HLA which controls the strongest stimulatory determinants for MLC now known as the HLA-D region was different from the class I encoding genes was already suggested in two early studies. Definitive evidence in this regard came from the studies of Yunis and Amos 1971. It is our purpose in this paper to discuss our current knowledge of the HLA-D region from the T cell perspective, an area that has been recently reviewed. The use of techniques that allow definition of determinants recognized by T lymphocytes and associated with HLA class II molecules has, thus, allowed definition of further polymorphisms not recognized with currently availablecharacterized serological reagents. Given the intimate relationship thought to exist between T lymphocyte recognition and major histocompatibility complex encoded molecules, definition of this LD T lymphocyte defined, polymorphism may be of the greatest import.