Diminished mixed lymphocyte reaction in ankylosing spondylitis, relatives, and normal individuals all with HL-A 27.

The mixed lymphocyte reaction against a pool of blocked lymphocytes was studied in individuals with and without HL-A 27, including controls, spouses, parents, sibs, and offspring, and patients with ankylosing spondylitis. In controls without HL-A 27 the mean increment of counts perminute was 46,630 compared with 29,860 in asymptomatic controls and relatives with HL-A 27 and 26,277 in spondylitic patients with HL-A 27. The mean response was also reduced to 34,902 in sibs and offspring without HL-A 27, and to 20,916 in three patients with spondylitis in the absence of HL-A 27.