The CMRF-35H gene structure predicts for an independently expressed memberof an ITIM/ITAM pair of molecules localized to human chromosome 17

The CMRF-35 monoclonal antibody recognizes an epitope found on at least two cell surface molecules, differentially expressed by many leukocytes, These molecules, the CMRF-35H (9) and CMRF-35A (CMRF-35) antigens are both membe rs of the immunoglobulin (Ig) superfamily with a single V-like Ig domain. T he function of these molecules is unknown, however the presence of putative immunoreceptor tyrosine-based inhibitory motifs (ITIM) in the cytoplasmic domain of the CMRF-35H molecule suggests that this molecule may play a regu latory role in leukocyte function. The CMRF-35H and CMRF-35A molecules show several similarities to the family of molecules containing ITIM or immunor eceptor tyrosine-based activatory motifs (ITAM) suggesting that CMRF-35H/CM RF-35A may be new members of this family. This would further indicate that, like other ITIM/ ITAM containing molecules, CMRF-35H/CMRF-35A will also pl ay an important role in the immune response. To further characterize these molecules, we have isolated genomic clones for the CMRF-35H gene and determ ined its intron-exon organization. The gene spans approximately 12 kb and c onsists of seven exons, Furthermore, this gene has been mapped to chromosom e 17 and thus is not linked to the known human ITIM containing genes which map to human chromosome 19 or the recently characterized molecule, NKp44, l ocalized to human chromosome 6.