CD6

null CD6 is a lymphocyte surface receptor of the scavenger receptor cysteine-rich (SRCR) superfamily containing three extracellular SRCR domains. Its principal ligand is ALCAM (CD166) on activated leukocytes and stromal cells, and the CD6-ALCAM pair stabilizes immunological synapse formation between T cells and antigen-presenting cells. Cytoplasmic motifs in CD6 recruit adaptor proteins that modulate TCR signaling and adhesion. CD6 is expressed on T cells, a B cell subset, and certain neurons. The humanized anti-CD6 antibody itolizumab is approved in some countries for psoriasis and is being evaluated in chronic graft-versus-host disease, illustrating CD6 as a druggable immune regulatory target.