Novel transcripts encoding secreted forms of feline CD80 and CD86 costimulatory molecules

Engagement of costimulatory molecules such as CD28 or CD152 (CTLA4) on T cells by CD80 (B7-1) or CD86 (B7-2) dictates the nature of T cell-mediated immune responses. We previously reported the discovery of naturally occurring forms of canine CD80 and CD86 mRNAs which encode secreted CD80 and CD86 molecules. We report here that mRNAs for secreted forms of CD80 and CD86 are also expressed in cats. The mRNA for secreted feline CD86 is generated by deleting a transmembrane domain exon, which is the same mechanism we described for secreted canine CD86. We also identified a feline CD80 transcript that only retains the immunoglobulin variable-like domain. The detection of naturally occurring mRNAs encoding secreted CD80 and CD86 adds further complexity to the regulation of the B7-CD28/CD152 costimulatory pathway.