Sheep CD4(+) alphabeta T cells express novel members of the T19 multigene family.
The sheep T19 multigene family contains at least 50 genes which are thought to be expressed exclusively on gammadelta T cells. The archetypal T19 molecule (represented by a full-length cattle cDNA clone termed WC1) is thought to have a relative molecular mass of about 220 000 and to contain 11 scavenger receptor cysteine rich (SRCR) repeats and a long cytoplasmic tail. In this study, purified CD4(+) and gammadeltaTCR+ sheep lymphocytes were examined by reverse transcriptase-polymerase chain reaction for the expression of T19 molecules. As expected, gammadelta T cells were found to express T19 molecules which closely resembled the archetypal form. However, CD4(+) alphabeta T cells were found to express at least two different types of T19 molecules; one resembled the previously described T19 molecules of gammadelta T cells which possessed the archetypal WC1-like structure, but a novel type of T19 variant which lacked SRCR domains 10 and 11 was also found in CD4(+) T cells but not gammadelta T cells. This novel molecule exhibited an unusual, incomplete SRCR repeat 9 joined directly to a hinge region. The transmembrane and cytoplasmic domains of this unusual T19 variant resembled the cattle T19 clone WC1, except that a complete exon within the cytoplasmic region was missing. These results, in contradistinction to existing serological data, suggest that expression of the T19 gene family is not confined to gammadelta T cells. Selected T19 genes are apparently expressed within CD4(+) T cells and possibly other lymphocytes as well.
O'Keeffe
M A
MA
Department of Veterinary Science, The University of Melbourne, Cnr Park Dve and Flemington Rd, Parkville, VIC 3052, Australia.
Metcalfe
S A
SA
Cunningham
C P
CP
Walker
I D
ID
D000595:Amino Acid Sequence; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism*; D002417:Cattle; D003001:Cloning, Molecular; D005091:Exons / Q000235:genetics; D005260:Female; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D005810:Multigene Family; D011487:Protein Conformation; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000032:analysis*; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000032:analysis; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D012756:Sheep / Q000235:genetics / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000378:metabolism*
D008565:Membrane Proteins; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016692:Receptors, Antigen, T-Cell, gamma-delta; C092286:T19 protein, Ovis aries