Mixed leukocyte reaction and hl-a specificity at multiple sclerosis.

Compared with the mixed leukocyte reaction (MLR) between cells from healthy individuals, the MLR between cells from two patients with multiple sclerosis (MS) is, on average, reduced in strength. There is a tendency for the most marked reduction of MLR to occur when both or neither of the members in a tested pair carry HL-A7, and when cells from patients in a relatively early stage of the disease (short duration, relapses but no permanent disablement) are studied; especially when cells from these patients are used as reactor clels in the MLR. Repeated studies of the same cell combinations with varying intervals showed that when both members of the pair carry HL-A7,--and therefore have a large chance also to carry LD-7a--the MLR strength is relatively constant. When only one or neither of the members carry HL-A7, the strength of MLR varies considerably. Probably two different mechanisms exist in MLR impairment: similarity of LD genes, and "immunosuppressive" factors which can vary during the course of the disease.