The predicted amino acid translation of the feline CD9 R.A.C.E. product was compared with the bovine, murine and human sequences (Fig. 2). The fCD9 R.A.C.E. product displayed 95.1% similarity to human CD9, 93.8% similarity to murine CD9 and 90.7% similarity to bovine CD9 at the amino acid level. Alignment of the four sequences demonstrated a high degree of homology with the majority of sequence variation clustering in the two predicted extracellular domains. The first, small extra¬cellular domain of feline CD9 (amino acids 36-53) lacks the two additional amino acids found in human CD9