MOLECULAR-CLONING AND EXPRESSION OF FELINE CD3-EPSILON

The cDNA of feline CD3 epsilon, one of the T-cell receptor components, was cloned from a feline T-lymphoblastoid cell line (MYA-1 cells) and peripheral blood, mononuclear cells and thymocytes of cats by polymer ase chain reaction. Sequencing analysis revealed that the open reading frame of feline CD3 epsilon consists of 606 base pairs encoding a pre dicted molecular mass of 25 kDa transmembrane protein which lacks N-gl ycosylation site. Comparison of the predicted amino acid sequence of f eline CD3 epsilon with those of other mammalians' homologues revealed that a relatively low homology was present in the extracellular domain . However, the cytoplasmic domain contained several characteristic mot ifs highly conserved across the species. These motifs were known to be important for signal transduction upon T-cell activation or endoplasm ic reticulum retention. In addition, the feline CD3 epsilon protein wa s expressed in an insect cell line (Sf9) by a baculovirus expression s ystem. The expression was confirmed by indirect immunofluorescence ass ay and immunoblotting analysis using an anti-human CD3 epsilon polyclo nal antibody. These results will provide additional information for un derstanding the feline immune system. (C) 1998 Published by Elsevier S cience B.V. All rights reserved.