Systemic lupus erythematosus (SLE) T cells display a hyperactive calcineurin/NF‐AT pathway. The aim of this study was to determine whether this pathway is responsible for the aberrant SLE T cell function and to test the effectiveness of the recently recognized calcineurin inhibitor dipyridamole in limiting SLE‐related pathology.

T cells and mononuclear cells were isolated from the peripheral blood of SLE patients and healthy individuals. Murine cells were isolated from the spleens and lymph nodes of lupus‐prone MRL/lpr mice and control MRL/MpJ mice. Cells were treated in vitro with tacrolimus, dipyridamole, or control. MRL/lpr mice were injected intraperitoneally with 50 mg/kg of dipyridamole 3 times a week for 3 weeks.

MRL/lpr T cells, especially CD3+CD4–CD8– cells, displayed a robust calcium influx upon activation and increased levels of NF‐ATc1. MRL/lpr T cells (both CD4+ and CD3+CD4–CD8– cells) provided help to B cells to produce immunoglobulin in a calcineurin‐dependent manner. Dipyridamole treatment of SLE T cells significantly inhibited CD154 expression, interferon‐γ, interleukin‐17 (IL‐17), and IL‐6 production, and T cell–dependent B cell immunoglobulin secretion. Treatment of MRL/lpr mice with dipyridamole alleviated lupus nephritis and prevented the appearance of skin ulcers.

NF‐AT activation is a key step in the activation of SLE T cells and the production of immunoglobulin. Dipyridamole inhibits SLE T cell function and improves pathologic changes of the disease in lupus‐prone mice. We propose that dipyridamole can be used in treatment regimens for patients with SLE.