Negative regulator of T-cell proliferation. Isoform 2 is present in the nuclear, vesicle and plasma membranes, isoform 3 is found in cytoplasmic vesicle structures and is not membrane bound. Expressed in brain, heart, kidney, liver, pancreas, ovary, leukocyte, small intestine, testis and thymus. By pro-inflammatory cytokines such as TNF and IL1B/interleukin-1 beta. Disease susceptibility is associated with variants affecting the gene represented in this entry. A nucleotide transition affecting a splice donor site results in the use of an alternative splice site and the production of isoform 3. Individuals expressing isoform 3 have a higher risk for sarcoidosis. Belongs to the immunoglobulin superfamily. BTN/MOG family.