Signal-regulatory protein gamma (SIRPG/SIRP gamma) also known as CD172 antigen-like family member B, CD172g, and CD172g antigen, is a member of the signal-regulatory protein (SIRP) family, and also belongs to the immunoglobulin superfamily. SIRP family members are receptor-type transmembrane glycoproteins known to be involved in the negative regulation of receptor tyrosine kinase-coupled signaling processes. SIRPG/SIRP gamma/CD172g is a probable immunoglobulin-like cell surface receptor. On binding with CD47, SIRPG can mediate cell-cell adhesion. SIRPG/SIRP gamma is engagement on T-cells by CD47 on antigen-presenting cells results in enhanced antigen-specific T-cell proliferation and costimulates T-cell activation. SIRPG/SIRP gamma/CD172g is detected in liver, and at very low levels in brain, heart, lung, pancreas, kidney, placenta and skeletal muscle. Expressed on CD4+ T-cells, CD8+ T-cells, CD56-bright natural killer (NK) cells, CD20+ cells, and all activated NK cells. This cytokine is mainly present in the paracortical T-cell area of lymph nodes, with only sparse positive cells in the mantle and in the germinal center of B-cell follicles. In the thymus, SIRPG is primarily expressed in the medulla on mature T-lymphocytes that have undergone thymic selection.