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CD154, also known as CD40 ligand （CD40L） or gp39, is a type II transmembrane protein belonging to the tumor necrosis factor （TNF） superfamily. It is primarily expressed on activated CD4+ T cells and can also be found on other immune cells such as CD8+ T cells, natural killer cells, platelets, dendritic cells, and endothelial cells. CD154 can form a trimeric structure and is crucial for humoral and cellular immunity. Its interaction with CD40, its classical receptor, is essential for B cell activation, proliferation, isotype switching, and germinal center formation. This interaction also plays a significant role in T cell priming and cell-mediated immune responses. In addition to CD40, CD154 can bind to several integrins, including αIIbβ3, α5β1, and αMβ2, which are involved in various inflammatory and immune processes. Abnormal expression of CD154 has been implicated in several autoimmune diseases, such as systemic lupus erythematosus （SLE）, where it contributes to the overproduction of autoantibodies and inflammation.