title: Selective deletion of antigen-specific, activated T cells by a humanized MAB to CD2 (MEDI-507) is mediated by NK cells.
abstract: CD2 is a 50-kDa transmembrane glycoprotein that plays an important role in T and natural killer (NT) lymphocyte functions. CD2 serves as both an adhesion molecule and as a costimulatory molecule through interactions with its ligand, CD58, on antigen presenting or target cells. Consistent with earlier studies using a rat anti-CD2 mAb, we have shown that treatment of alloantigen stimulated T lymphocytes with a humanized mAb, MEDI-507 (IgG1, kappa), induced hyporesponsiveness to subsequent stimulation with alloantigen but not to mitogen (phytohemagglutinin). Fluorescence-activated cell sorting analysis of cells from mixed lymphocyte reaction (MLR) treated with MEDI-507 revealed pronounced deletion of T and NK cells, consistent with lack of proliferation in the MLR. MEDI-507 F(ab')2 fragments did not have inhibitory activity or induce deletion of lymphocytes in the MLR. Removal of the NK cell subset by magnetic bead depletion using anti-CD16 and anti-CD56 mAbs eliminated both the T cell deletion and the inhibitory effect. Reconstitution of NK depleted responder populations using autologous NK cells restored the MEDI-507-mediated deletion activity to levels measured in the original MLR. Formaldehyde-fixed NK cells failed to mediate the MEDI-507-induced deletion effect. Altogether, our studies indicate that activated T cells with MEDI-507 bound to CD2 are preferential targets for autologous NK cells through a nonapoptotic cytotoxic mechanism.
authors.affiliation: Department of Immunology and Molecular Genetics, MedImmune, Inc., Gaithersburg, Maryland 20878, USA.
authors.forename: L
authors.initials: L
authors.lastname: Branco
authors.forename: P
authors.initials: P
authors.lastname: Barren
authors.forename: S Y
authors.initials: SY
authors.lastname: Mao
authors.forename: D
authors.initials: D
authors.lastname: Pfarr
authors.forename: R
authors.initials: R
authors.lastname: Kaplan
authors.forename: C
authors.initials: C
authors.lastname: Postema
authors.forename: S
authors.initials: S
authors.lastname: Langermann
authors.forename: S
authors.initials: S
authors.lastname: Koenig
authors.forename: S
authors.initials: S
authors.lastname: Johnson
mesh_terms: D000328:Adult; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D015703:Antigens, CD / Q000276:immunology; D018801:CD2 Antigens / Q000276:immunology*; D002478:Cells, Cultured; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D007694:Killer Cells, Natural / Q000276:immunology*; D008213:Lymphocyte Activation; D007959:Lymphocyte Culture Test, Mixed; D008212:Lymphocyte Depletion / Q000379:methods; D051381:Rats; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018801:CD2 Antigens; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G