IDENTIFICATION OF A CD4 HOMOLOG IN THE CAT

Abstract: : Monoclonal antibody, Fel 7, produced against cat T cells, was found to react with a single‐chain glycoprotein of Mr 65,000 present on a majority of the thymocytes, 40% of lymph node cells, 15% of splenocytes and 25% of blood mononuclear cells. Using a previously reported antibody that recognizes the feline CD8 antigen, approximately 65% of cat thymocytes were shown to express both the Fel 7 and fCD8 antigens, while 14% and 6% expressed either the Fel 7 or the fCD8 determinant respectively. The Fel 7 and fCD8 antigens were expressed by mutually‐exclusive subpopulations of peripheral T cells, and not by B cells, macrophages or other types of blood cells. Expression of the Fel 7 antigen was down‐regulated and the molecule was phosphorylated when T cells were stimulated with phorbol ester, while the expression of the fCD8 antigen was unaffected by this treatment. The addition of soluble Fel 7 antibodies efficiently blocked Con A‐induced proliferation of T cells in a dose‐dependent manner. The data suggest that the mAb Fel 7 identifies a feline CD4 homologue, providing an important reagent for the study of normal and abnormal T cell development in cats. Copyright © 1990, Wiley Blackwell. All rights reserved