Clone REA469 recognizes the human CD199 antigen, a multi-pass membrane protein which is also known as C-C chemokine receptor type 9 (CCR9) or G-protein coupled receptor 28 (GPR28). CD199 is a receptor for the chemokine thymus-expressed chemokine (TECK) and a member of the G protein coupled receptor family (GPCR). The main function of GPCR family members is to send signals into the cell after the activation of G-proteins and they are known for their roles in inflammation, leukocyte trafficking, and immune differentiation. CD199 subsequently transduces a signal by increasing the intracellular calcium ions level. It influences T cell development at several stages within the thymus. In peripheral blood, CD199 is expressed by naive CD8+
T cells, but not by naive CD4+
T cells. It is furthermore selectively expressed on plasmacytoid dendritic cells of immature phenotype in vivo
. Different studies have shown the involvement of the CD199-TECK axis in colorectal, prostate, ovarian, and breast cancers.