ABSTRACT
Early studies in histocompatibility focused on the number of genes that evoke graft rejection.Initially, (H ) genes were treated together as a set and the size of this set was the most important question. Not until George Snell isolated H genes in congenic strains1 could an individual H gene’s function be studied-as amply demonstrated with the H 2 complex. Excluding H 2 for now, subsequent studies on histocompatibility genetics still have an impact on our concept of the size of the H gene set even though those studies might have been designed to reveal other properties. In this limited review I want to concentrate on H set size; I find that there are many good reasons for H-set size to be more extensive than early studies indicated. [For more comprehensive reviews of minor H genes see refs. 2,3.] I also want to speculate on how H genes fit into the scheme of things; just what should we expect H gene functions to be? To give perspective as well as a personal touch, I will relate how the results from various H gene studies as they were encountered caused a research project in which I was involved to be modified as that project unfolded during the 1960s and 1970s.
