New Hamster Monoclonal Antibodies

the TCR-CD3 complex and peptide-presenting MHC products, which contribute to the interaction of APC and Tlymphocytes. Most notable are mAbs against CD4 and CD8 (1, 2), andlymphocyte function-associated antigen 1 (CDlla, LFA-1)t (3) and its ligand, intercellular adhesion molecule 1 (CD54, ICAM-1) (4). Each mAb inhibits antigen-driven T cell proliferation when antigen is presented by a variety of APC, including one of the most potent, dendritic cells (5). An early step in a primary immune response is the association ofTcells andAPC in discrete, long-lived (days), aggregates (6, 7) . However, none of the known molecules on either T cells or dendritic cells appears essential for the early stages of cluster formation in mice, primarily because rat mAbs directed against these molecules do not block the formation ofsizeable aggregates in the murine MLR (5). For example, mAbs to LFA-1 inhibit the binding between T cells and activated B cells but fail to inhibit initial dendriticT cell clustering (8). Recently, when the rat has proved to be a difficult host for preparing mAb to structurally conserved murine molecules, several investigators have used Armenian hamsters as a host (9-11) . We adopted a similar approach to search for mAbs that would inhibit dendriticT cell clustering or would bind to dendritic cells in a novel assay using the FACS. We report here the isolation of two newanti-mouse leukocyte integrin mAbs: 2E6, which recognizes a determinant common to all members of the 02 integrin family and N418, which identifies a distinct p150,90 member ofthe family, possibly CDllc. Using these new reagents, we describe the distinct expression and function of leukocyte integrins on spleen dendritic cells .