Lymphocyte abnormalities in ankylosing spondylitis

SUMMARY Peripheral blood T (SRBC rosette) and B (AgG- and C-receptor) lymphocyte sub-populations and responsiveness to phytohaemagglutinin (PHA) were assayed in 40 patients with ankylosing spondylitis and in 55 normal subjects. There was no significant difference in the lymphocyte concentrations or responsiveness to PHA between the two groups. However, the percentages of T lymphocytes were significantly lower in the patients irrespective of their HLA typing. This was probably due to an increase in the 'null ' population since the percentages of both the AgG- and C-receptor cells were normal. Recent studies have shown that one histocompati-bility antigen of the second segregant series, HLA B27, is highly associated with a whole group of rheumatic diseases, the seronegative spondylo-arthropathies (Brewerton and James, 1975; Goldin and Bluestone, 1976). Ankylosing spondylitis (AS) in particular provides the strongest evidence we have ofdisease susceptibility beingrelated to the possessio