ICOS and systemic lupus erythematosus: In MRL/lpr mice, the abnormally high expression of Tfh‐associated molecules, such as ICOS, PD‐1, BCL‐6 and IL‐21, suggests that Tfh cells may play a crucial role in the pathogenesis of SLE, which is closely connected with autoantibody production and/or lupus‐like symptoms.15, 16, 17, 18, 19