Phenotypic expressions of the major histocompatibility locus in man (HL-A): leukocyte antigens and mixed leukocyte culture reactivity.

The evidence is reviewed that a single genetic system, the major histocompatibility locus in man, HL-A, determines most of the antigens measured by presently available leukocyte isoantisera, and also controls reactivity in one-way mixed leucocyte culture tests. Studies in 12 families are presented to support this conclusion. Some interesting exceptions to the general typing-MLC tests correlation are presented and discussed.