Involvement of Lymphocyte Function-Associated Antigen-1 and Intercellular Adhesion Molecule-1 in Monocyte and T-Cell Antigen-Specific Interactions

Abstract

The cell surface molecules directly involved in the specific interaction between T cells and monocytes have been well described—MHC class II molecules and processed antigen on the monocyte side and the antigen specific receptor on the T cell side. These minimal requirements for antigen presentation have been simulated by using T cells and as accessory cell, “null” cells such as the murine L cell, transfected with human MHC class II products (1). Most of these studies have been successful only with cloned T cell lines and not with resting T cell populations such as would be found in peripheral blood. This has led to the suggestion that other molecular interactions are required to activate such cells (2,3). T cells, particularly CTL, use the adhesion molecule lymphocyte function-associated antigen-1 (LFA-1) to interact with target cells (4). The molecule to which LFA-1 binds in many but not all, of these interactions is intercellular adhesion molecule-1 (ICAM-1) (5,6). We have examined the role of the leukocyte integrin family, namely LFA-1, CR3/Mac-1 and p150,95 in the early interaction between resting T cells and monocytes which is required for the generation of antigen specific T cell proliferation. These molecules are all well expressed by monocytes, whereas T cells express LFA-1 with CR3 and p150,95 found only on a subset of CD8+T cells (7,8).