The B- and T-lymphocyte attenuator (BTLA) protein is a member of the immunoglobulin superfamily containing a single immunoglobulin (Ig) domain. Like other coihibitory receptors such as CTLA-4 and PD-1,BTLA functions as a receptor that relays inhibitory signals to suppress the immune response,and can inhibit LPS-induced endotoxic shock by suppressing TLR4 signaling in innate immune cells. Polymorphisms in this gene have also been associated with an increased risk of rheumatoid arthritis