Measurement of antibody-producing capacity to flagellin in man. IV. Studies in autoimmune disease, allergy and after azathioprine treatment.

Humoral immune responses after primary and secondary immunization with monomeric flagellin from Salmonella adelaide were examined over 10 weeks in three groups of patients with putative autoimmune disease, i.e. systemic lupus erythematosus, rheumatoid arthritis and lupoid hepatitis, in patients with allergy to an extrinsic antigen, and in azathioprine treated patients. Sera were titrated by tanned cell haemagglutination for total antibody and IgG antibody. In patients with autoimmune diseases and allergy the humoral immune response to flagellin was similar to that of matched controls with other illnesses, so that neither autoimmunity nor allergy could be attributed to any general `overactivity' of the antibody producing system. In patients with autoimmune diseases treated with azathioprine there was no statistically significant depression of the primary or secondary humoral immune response to flagellin, as compared with appropriate controls. This could be explained by azathioprine having a predominantly anti-inflammatory action, influencing cellular more than humoral immune mechanisms, in being `tolerogenic' in respect of autoantigens, or by a combination of these effects.