Cell surface expression of human FcγRI, II, and III; HLA class I and II; CD4; CD14; and IL-2R molecules in U937 cells expressing HIV-1 Nef or HIV-1 fen. U937 cells were transduced with retroviral vector containing nef or fenand selected after treatment with G418. Selected cells expressing Nef and Fen were cultured and analyzed for cell surface molecules as described in Fig 6. Downregulation of FcγRI and II and CD4 and upregulation of HLA class I molecules and no change in HLA class II, CD14, and IL-2R were observed in the Nef-expressing population of U937 cells.