Three distinct antigens associated with human T-lymphocyte-mediated cytolysis: LFA-1, LFA-2, and LFA-3.

Abstract

Monoclonal antibodies were prepared to anti-HLA-DR cytolytic T lymphocytes (CTLs) and screened for inhibition of CTL-mediated killing. Binding of monoclonal antibodies to four types of molecules, LFA-1, LFA-2, LFA-3, and HLA-DR, inhibited killing, suggesting that these molecules participate in the CTL-target cell interaction. The antigens were characterized by immunoprecipitation, crosslinking, NaDodSO4/polyacrylamide gel electrophoresis, and immunofluorescence flow cytometry. The LFA-1 antigen contains a and ,B polypeptide chains of Mr 177,000 and 95,000 that are noncovalently associated in an alp, structure. It is present on both B and T lymphocytes and marks subpopulations that differ in quantitative expression. Human LFA-1 appears to be the homologue of mouse LFA-1. Human LFA-2 is of Mr 49,000 with a minor component of Mr 36,000. It is expressed on CTL lines but not on a B-cell line and in peripheral blood preferentially on T lymphocytes. Human LFA-3 is of Mr 60,000 and is expressed on both B and T lymphocytes.Antigen-specific T-lymphocyte-mediated killing is a multistep process involving antigen recognition and adhesion of the cytolytic T lymphocyte (CTL) to the target cell, delivery of the lethal hit, and target cell lysis (1)(2)(3). Bystander cells and the CTL itself are unharmed in the killing reaction, and the CTL can detach and engage in further killing encounters. The molecular basis ofCTL-mediated killing is ofconsiderable interest, both in itself and for our understanding of T lymphocyte-mediated immunity in general. In previous studies designed to identify the molecules involved in mouse CTL-mediated killing, rat monoclonal antibodies (MAb) were prepared to mouse CTLs and screened for their ability to inhibit killing (4)(5)(6)(7)(8)(9). MAb to the Lyt-2,3 and lymphocyte function-associated 1 (LFA-1) antigens, but not MAb to many other types ofsurface structures, were found to inhibit killing. The LFA-1 antigen appears generally important in mouse T-lymphocyte immune interactions, since MAb to it block not only allogeneic and xenogeneic CTLmediated killing but also T-helper-cell antigen-specific proliferative responses and T-cell-dependent B-cell responses (4). Anti-LFA-1 MAb exert their effect on killing by binding to the CTL rather than to the target cell and block the formation of CTL-target conjugates and the Mg2+-dependent adhesion step but not the Ca2+-dependent lethal hit stage (4, 7). The mouse LFA-1 antigen contains two noncovalently associated polypeptide chains of Mr 180,000 and 95,000 (10, 11). No human homologue of mouse LFA-1 has been defined, but is the human homologue of Lyt-2,3 (12).We have probed the molecular mechanisms of human T-lymphocyte-mediated killing by preparing MAb to human anti- (14,15) are associated with CTL-mediated killing; however, none of these antigens has thus far been shown to be the T-cell antigen receptor. Direct screening for MAb blocking killing should be a more efficient method ofidentifying the antigen receptor and other molecules involved in C...

An isolated, surface-expressed I domain of the integrin αLβ2 is sufficient for strong adhesive function when locked in the open conformation with a disulfide bond

“…** Monoclonal Antibodies. The mouse anti-human ␣L (CD11a) mAbs TS1͞22, TS2͞4, the activating anti-␤2 (CD18) mAb CBR LFA-1͞2, and the nonbinding myeloma IgG X63 have been described previously (20,21).…”

Expression of a structural domain of the β2 subunit essential for αMβ2 ligand recognition

“…The murine monoclonal anti-␣ M antibody 904 [19] was used as culture supernatant. Also used as purified IgG fractions were the anti-␤ 2 murine monoclonals 2D8 [32], 8H1 [31], and TS1/18 [38]. Purified anti-␤ 2 murine monoclonal, mAb R15.7, was kindly provided by R. Rothlein (Boehringer Ingelheim, Ridgefield, CT) [39].…”

Both LFA‐1‐positive and ‐deficient T cell clones require the CD2/LFA‐3 interaction for specific cytolytic activation

“…Numerous studies have demonstrated that LFA-1 is particularly involved in the conjugate binding step that precedes lysis of the target, cells [3,[7][8][9]51]. Several investigations carried out with peripheral blood lymphocytes from LAD patients, whose leukocytes lack LFA-1 at the cell surface, demonstrate that T cell functions are impaired [52,53], However, Mazerolles etal.…”

“…These heterodimeric adhesion molecules are each composed of a unique a chain and share a common p chain, the p2 chain of the integrins [4]. Various studies demonstrate that the interaction of LFA-1 with its counterstructures ICAM-1 [5] and ICAM-2 [6] plays a major role in antigen-presenting cell/responder cell, and cytotoxic effector cell/target cell interactions [7][8][9]. The physiological importance of the LFA-1 receptor family is demonstrated in patients with a serious immunodeficiency This disease is caused by the complete (severe type) or partial (moderate type) absence of cell surface expression of these adhesion receptor molecules [10][11][12][13].…”