Anti-CD3 In Vivo Antibody - Low Endotoxin (UCHT-1) recognizes Human CD3. anti-Human CD3 recognizes a (Mr 22-28 kDa) T-cell surface glycoprotein. The epitope recognized by the CD3 antibody is expressed on a constant region of the epsilon chain of the CD3 antigen/T-cell receptor complex (TCR)