Delayed effect of tumour necrosis factor antagonists on lymphocyte proliferation. Infliximab (Ifx), adalimumab (Ada), etanercept (Eta), or an anti-interleukine (IL)-12 monoclonal antibody (mAb) was added either at the initiation of culture or on day 2 or 5 to peripheral blood mononuclear cells stimulated with purified protein derivative. Thymidine incorporation was determined on day 7. Results (mean ± standard error of the mean) are expressed as the proportion of controls (performed in the presence of a control antibody). *p < 0.05 and **p < 0.01. n = 10 for Ifx, Ada, and Eta, and n = 3 for the anti-IL-12 mAb.