Anti-C33 antibodies are protein reagents that detect specific antigens. The C33 antigen is another term for the human protein CD82 molecule, encoded by the CD82 gene. The protein is reported to associate with CD4 or CD8 and delivers costimulatory signals for the TCR/CD3 pathway. Canonically, it has an amino acid length of 267 residues and a mass of 29.6 kilodaltons. Its subcellular localization is in the cell membrane and it is reported to have lymphoid specific expression. The C33 protein is a member of the Tetraspanin (TM4SF) protein family.