BOTH HUMAN ALPHA BETA AND GAMMA INTERFERONS UP-REGULATE THE EXPRESSION OF CD48 CELL-SURFACE MOLECULES/

We have established a cDNA library from interferon (IFN)-treated human lymphoblastoid Daudi cells and made use of differential screening to search for yet unidentified IFN-regulated genes. In the course of thes e studies, we have isolated a human cDNA coding for the glycosyl-phosp hatidylinositol-linked (GPI) membrane glycoprotein CD48 (TCT-1, Blast- 1). Various studies demonstrated that the murine CD48 is the predomina nt counterreceptor for the mouse CD2 and is involved in the regulation of T cell activation, Since the murine CD48 is functionally homologou s to the human CD2 ligand LFA-3 (CD58), the function of the human CD48 remains unknown, In this report, we show that both Hu-IFN-alpha/beta and Hu-IFN-gamma increase the level of CD48 mRNA and upregulate the ex pression of CD48 proteins at the surface of various cultured human cel l lines. However, the IFN have no effect on the expression of LFA-3, I n addition, we show that IFN increase CD48 expression on peripheral bl ood mononuclear CD3(+), CD14(+), and CD19(+) subpopulations, These dat a suggest that in addition to modulation of the conventional MHC class I and class II-restricted interactions, the IFN might promote MHC-unr estricted interactions of target cells with the immune cells by induci ng the expression of the cell surface CD48 molecule.