title: The anti-CD2 monoclonal antibody BTI-322 generates unresponsiveness by activation-associated T cell depletion.
abstract: The antihuman CD2 MoAb BTI-322 (Lo-CD2a) effectively inhibits T cell responses in vitro to allogeneic cells, which is followed by unresponsiveness to the original stimulator in secondary stimulation. We studied the xenogeneic human antiporcine mixed lymphocyte reaction (MLR), and utilized anti-T cell receptor (TCR) Vbeta family antibody-induced cell proliferation to determine the specificity and mechanism. BTI-322 and its humanized version, MEDI-507, effectively inhibited the primary xenogeneic MLR. After suboptimal primary stimulation using lower numbers of xenogeneic stimulator cells, the unresponsiveness in secondary culture was apparent only for xenogeneic stimulator cells of the original SLA haplotype, and not for third-party stimulators or allogeneic cells. The inhibition of primary MLR was not observed for nylon-wool-purified T cells, but was seen after reconstitution of purified T cells with monocytes. Similarly, anti-Vbeta family-specific stimulation showed family-specific unresponsiveness in secondary culture. This required the presence of the whole BTI-322 molecule: a F(ab')2 fragment was not effective. T cells of a distinct Vbeta family were depleted after stimulation with an anti-Vbeta family-specific antibody and BTI-322. We conclude that the inhibition by BTI-322 of a primary xenogeneic MLR or the response to an anti-TCR Vbeta antibody is associated with unresponsiveness upon restimulation, due to activation-associated cell depletion. In this process, the interaction between monocytes and the Fc part of the antibody is involved. This unique characteristic of BTI-322 suggests the potential of the antibody for tolerance induction in vivo, besides the potential use as a T cell depleting agent.
authors.affiliation: BioTransplant Incorporated, Charlestown, MA USA. Yuanxin.Xu@genzyme.com
authors.forename: Y
authors.initials: Y
authors.lastname: Xu
authors.forename: D
authors.initials: D
authors.lastname: Kolber-Simonds
authors.forename: J A
authors.initials: JA
authors.lastname: Hope
authors.forename: H
authors.initials: H
authors.lastname: Bazin
authors.forename: D
authors.initials: D
authors.lastname: Latinne
authors.forename: R
authors.initials: R
authors.lastname: Monroy
authors.forename: M E
authors.initials: ME
authors.lastname: White-Scharf
authors.forename: H-J
authors.initials: HJ
authors.lastname: Schuurman
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D061067:Antibodies, Monoclonal, Humanized; D000918:Antibody Specificity / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D002455:Cell Division / Q000276:immunology; D002478:Cells, Cultured; D000939:Epitopes / Q000276:immunology; D006801:Humans; D007108:Immune Tolerance / Q000276:immunology; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology; D007959:Lymphocyte Culture Test, Mixed / Q000379:methods; D008212:Lymphocyte Depletion; D009000:Monocytes / Q000276:immunology; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology; D013552:Swine; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D017252:CD3 Complex; D000939:Epitopes; C105249:LO-CD2a; D016693:Receptors, Antigen, T-Cell, alpha-beta; C544394:siplizumab