Downmodulation of CD3ε expression CD8α+β- T cells of feline immunodeficiency virus-infected cats

Feline immunodeficiency virus (FIV) infection in cats is associated with an increase of feline CID (fCD)8alpha(+) beta(-) and fCD8alpha(+) beta(low) cells in peripheral blood. To investigate these cells in more detail, an anti-fCD3epsilon mAb, termed NZM1, was generated, which recognizes the extracellular epitope of the fCDepsilon molecule. The anti-fCDepsilon mAb proved to be more suitable for identifying feline T cells than the anti-fCD5 one, which has been used as a pan-T-cell reagent in cats, because of the presence of fCD5(+)fCD3epsilon(-) cells among lymphocytes. Although the fCD8alpha(+) beta(-\) and fCD8(alpha+) beta(low) cells in the FIV-infected cats expressed fCD3epsilon, a subset of fCD8alpha(+)beta(-) cells expressed fCD3epsilon. antigen at a lower level than the T cells whose phenotype was fCD4(+), or fCDalpha(+)beta(low). The lower expression of fCD3epsilon. may be associated with the immune status of fCDBalpha(+)beta(-) T cells.