The protein encoded by this gene is expressed on the surface of T cells. It regulates B cell function by engaging CD40 on the B cell surface. A defect in this gene results in an inability to undergo immunoglobulin class switch and is associated with hyper-IgM syndrome.,CD154,CD40L,HIGM1,IGM,IMD3,T-BAM,TNFSF5,TRAP,gp39,hCD40L,CD40LG,Cell Biology & Developmental Biology,Apoptosis,Immunology & Inflammation,CD markers,Cytokines,TNF,B Cell Receptor Signaling Pathway,NF-kB Signaling Pathway,Cell Intrinsic Innate Immunity Signaling Pathway,Cardiovascular,CD40LG