Anti-CD8 In Vivo Antibody - Low Endotoxin (UCHT-4) recognizes Human CD8. Anti-Human CD8 recognizes a T-cell glycoprotein cell surface complex (Mr 32 kDa) which defines the cytotoxic/suppressor population of mature T-lymphocytes. The CD8 complex interacts with class I MHC molecules resulting in increased adhesion between CD8+ T-lymphocytes and their target cells. Binding of the CD8 antigen to Class I MHC molecules enhances T-cell activation. The cytoplasmic portion of the CD8 antigen is associated with a protein tyrosine kinase (p56lck).