Although humoral immune mechanisms are currently thought to be of pathogenetic significance in juvenile rheumatoid arthritis (JRA), little is known about the role of cellular hypersensitivity in this disease. A possible association between abnormalities of humoral and cellular immunity exists in patients with ataxia-telangiectasia, who may have absent IgA, abnormal delayed hypersensitivity, or both. As IgA deficiency has been noted in 2–3% of patients with JRA, we have studied selected aspects of humoral and cellular hypersensitivity in patients with JRA and IgA deficiency and in patients with JRA and normal IgA levels. All patients had normal serum levels of complement, IgG, IgM, and IgD.
Cellular hypersensitivity was evaluated by cutaneous delayed-type hypersensitivity, in vitro migration inhibitory factor production, and antigen induced 3H-thymidine incorporation by lymphocytes using Candida and Streptokinase–Streptodornase antigens. Two of four IgA deficient patients had positive in vitro but negative in vivo responses to antigens. Seven of fourteen JRA patients with normal immunoglobulin levels exhibited a similar dissociation of in vivo and in vitro manifestations of delayed hypersensitivity. This pattern of cellular immune response was associated with activity and chronicity of disease; it was independent of IgA deficiency.