Sulphasalazine inhibits human antigen-specific immune responses in vivo

Objective: To study the effects of the antirheumatic drug sulphasalazine (SASP) on the immune system by analysing systemic and gut-associated immune responses. Methods: A total of 23 healthy volunteers were treated with either SASP or placebo for 5 weeks in a double-blind fashion and immunised 2 weeks after the initiation of treatment. Specific immune responses were triggered by subcutaneous immunisation with tetanus toxoid and by peroral immunisation with inactivated influenza vaccine. The effects of treatment on specific immunity to tetanus and influenza were evaluated by enzyme-linked immunospot assay quantifying the number of circulating specific and total antibody-producing cells (spot-forming cells (SFC)) at 6, 8 and 10 days after immunisation. Results: An immunosuppressive effect of SASP on systemic immune response was observed with a decrease in the total number of IgG-SFC, IgG anti-tetanus SFC and IgG anti-tetanus antibody levels in serum. SASP also exerted an immunosuppressive effect on the mucosa-associated immune system as seen from its down-regulating effect on the total number of circulating IgA SFC. Conclusions: These data show firstly that SASP exerts an immunosuppressive effect on defined immune responses to immunisation in vivo, and secondly that both mucosa-associated and systemic immunity are affected by SASP treatment.