EFHD2, also known as Swiprosin-1 or SWS1, is an EF-hand and coiled-coil-containing adaptor protein that plays a role in lymphocyte physiology. EFHD2 exhibits the highest expression in CD8+ T cells and immature B cells. It provides a membrane scaffold that is required for the Syk-, SLP-65-, and PLCgamma2-dependent B-cell receptor (BCR)-induced calcium flux. EFHD2 may also regulate BCR-induced immature and primary B-cell apoptosis. It controls spontaneous apoptosis through the regulation of BCL2L1 abundance. Also, EFHD2 plays a role as negative regulator of the canonical NF-kappa-B-activating branch.