A Particular Subset of HLA-DR4 Accounts for All or Most of the DR4 Association in Type I Diabetes

Two human T-lymphocyte clones, derived from a mixed leukocyte culture (MLC) with stimulating cells from a type I diabetic patient, define a subset of HLA-DR4, tentatively called “DR4S.” In testing of 69 random type I diabetic subjects and 69 random controls, 79% (37/47) of DR4-positive patients, but only 44% (8/18) of DR4-positive controls, had DR4S (P < 0.01). The relative risk of type I diabetes for DR4S^{+ individuals} was 8.8,while that for DR4⁺ DR4S⁻ individuals was only 1.0. Thus, in the populationtested, DR4S accounts for all or most of the increased frequency of HLA-DR4 in type I diabetes.