Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a CD28 homologue wh
ich down-modulate T cell responses rather than augment them. To investigate
its biological role in feline immune system, we cloned and sequenced full-
length feline CTLA-4 (fCTLA-4) cDNA by RT-PCR from pokeweed mitogen stimula
ted peripheral blood lymphocytes. The fCTLA-4 contains an open reading fram
e of 669 nucleotides, coding for a polypeptide of 223 amino acids. The pred
icted fCTLA-4 amino acids sequence shows the homology of 86.6%, 87.0%, and
76.2% with human, bovine, and murine molecules respectively. The hexapeptid
e motif (MYPPPY) within the extra-cellular domain of CTLA-4 molecule, which
is believed to be responsible for interaction with the B7 family members,
is completely conserved in all the species.