CELLULAR IMMUNOLOGY 122,4 16-423 ( 1989) A Novel Monoclonal Antibody, 1 B3.1, Binds to a New Epitope of the VLA-1 Molecule ILAN BANK,* MARTIN HEMLER,~ MICHAEL B. BRENNER,~ DINA COHEN,* VERED LEVY,* JONATHAN BELKO,$ CAROL CROUSE,? AND LEONARD CHESS+ *Department of Internal Medicine and Oncology, Chaim Sheba Medical Center Tel Hashomer and Sackler School ofMedicine, Tel Aviv University, Israel; tDana Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115; and *Division of Rheumatology, Columbia University College of Physicians and Surgeons, New York, New York 10032 Received November 18, 1988; accepted May 7, I989 A monoclonal antibody, 1 B3.1, was raised against a cloned IL-2-dependent T cell line that expressesthe TrdT cell receptor. MoAb lB3.1 reacted with long-term cultured T cell lines of both T-@ and T&I lineage, and with in viva-stimulated T cells, derived from synovial fluid, but not with resting or short-term activated T cells, B cells, or macrophages. Immunoprecipitation of the 1 B3.1 target antigens showed that 1 B3. I recognizes a 200/I 10 kDa molecule that is identi- cal to the VLA- 1 heterodimer precipitated by MoAb TS2/7. 1 B3.1, however, binds to an epitope of VLA- 1 that is distinct from the TS2/7 binding site. This new MoAb could be useful in further studies of the functions of VLA- 1, and of the cells that express this molecule. o 1989 Academic Press,Inc. INTRODUCTION Recently, it has been shown that members of a complex of proteins termed VLA or “very late antigens” are expressed on the surface of T cells after relatively pro- longed periods of activation (l-4). The VLA proteins constitute a family of six dis- tinct heterodimers (VLA-l-6), that all share a common 110 kDa (nonreduced, NR) VLA subunit, but differ in their (Y subunits, which range in their molecular weights (Mr) from 200 to 130 kDa and are termed (~1through (~6 (5, 25). The common /3 subunit of the VLA proteins is involved in cell adhesion to fibronectin and laminin and the VLA-5 heterodimer has been found to be identical to the human fibronectin receptor (6). The N-terminal sequences of the VLA (Y subunits are homologous to the (Y subunits of the LFA-1, Mac-l (CR-3), and P 150/95 molecular family, as well as to the vitronectin receptor-platelet GP IIb/IIIa family, and a position-specific (PS) antigen important in Drosophila embryogenesis (7). Many of these molecules recog- nize ligands containing Arg-Gly-Asp sequences and are members of the supergene integrin family of adhesive protein receptors which have been highly conserved dur- ing evolution (8,9). In long-term cultured T cells, the major VLA proteins expressedare VLA- 1 (200/ 110 kDa) and VLA-2 ( 165/ 110 kDa) (1,2). To a lesserextent, VLA-3 ( 150/l 10 kDa) is also expressed (5). The identification of these specific members of the VLA family was facilitated by the development of monoclonal antibodies (MoAbs) that specifi- cally recognize each heterodimer (4, 5, 10). In this paper we describe a new MoAb, 416 0008~8749189 $3.00 Copyright 0 1989 by Academic Press,Inc. All rights of reproduction in any form reserved.