Decrease of B-cells and autoantibodies after low-dose methotrexate

The purpose was to assess the efficacy of low-dose methotrexate (MTX) on immunological parameters in patients with lupus erythematosus (LE) under short- (≤10 weeks) vs. long-term (>10 weeks) conditions. Patients who did not respond to classical LE treatment (antimalarials and/or glucocorticosteroids) were retrospectively analyzed. Twenty-two LE-patients received 10–30 mg MTX per week. Sera and ethylenediaminetetra-acetic blood specimens were analyzed for autoantibodies and lymphocyte subsets (flow cytometry), respectively. Clinical improvement occurred in 21 patients (complete response n = 15, 68.2%). B-cells were the main targets: their absolute number significantly dropped down after long-term treatment (290 ± 49 vs. 221 ± 41 μl–1, P = 0.00254). This was accompanied by down-regulation of autoantibodies. The effect on B-cells was more pronounced in patients with (before vs. long-term 172 ± 34 vs. 99 ± 15 μl–1, P = 0.02853) than without autoantibodies (169 ± 40 vs. 144 ± 51 μl–1, P = 0.55406). MTX did not induce immunosuppression. Low-dose MTX has different short- and long-term effects on immunologic parameters, which could explain the clinical improvement.