Mediates B-cell proliferation in the absence of co- stimulus as well as IgE production in the presence of IL-4. Involved in immunoglobulin class switching. Defects in CD40LG are the cause of X-linked immunodeficiency with hyper-IgM type 1 (HIGM1); also known as X-linked hyper IgM syndrome (XHIM). HIGM1 is an immunoglobulin isotype switch defect characterized by elevated concentrations of serum IgM and decreased amounts of all other isotypes. Affected males present at an early age (usually within the first year of life) recurrent bacterial and opportunistic infections, including Pneumocystis carinii pneumonia and intractable diarrhea due to cryptosporidium infection. Despite substitution treatment with intravenous immunoglobulin, the overall prognosis is rather poor, with a death rate of about 10% before adolescence. Belongs to the tumor necrosis factor family. Note: This description may include information from UniProtKB.
Protein type: Membrane protein, integral; Cell adhesion
Cellular Component: extracellular space; integral to plasma membrane; integral to membrane; plasma membrane; external side of plasma membrane
SS: The number of records in which this modification site was determined using site-specific methods. SS methods include amino acid sequencing, site-directed mutagenesis, modification site-specific antibodies, specific MS strategies, etc.