title: Anti-CD3 antibodies OKT3 and hOKT3gamma1(Ala-Ala) induce proliferation of T cells but impair expansion of alloreactive T cells; aspecifc T cell proliferation induced by anti-CD3 antibodies correlates with impaired expansion of alloreactive T cells.
abstract: OKT3, a mouse anti-human CD3 monoclonal antibody (mAb), has been used for decades to reverse acute transplant rejection. A humanized OKT3 with two alanine replacements on the CH2 domain, hOKT3gamma1(Ala-Ala), was generated to reduce side effects of OKT3. This study reports the effects of OKT3 and hOKT3gamma1(Ala-Ala) on responder T cells in mixed leukocyte cultures (MLC). T cells were purified from peripheral blood mononuclear cells (PBMC) and labeled with CFSE before culture with irradiated allogeneic PBMC in a MLC. Multiparameter flow cytometric analysis of MLC demonstrated logarithmic expansion of T cells with a memory phenotype. Treatment with either OKT3 or OKT3gamma1(Ala-Ala) prevented the logarithmic expansion of these cells. Instead, both OKT3 and hOKT3gamma1(Ala-Ala) induced nonspecific expansion of T cells with both naive and memory phenotype. The proliferating T cells in OKT3 or hOKT3gamma1(Ala-Ala) treated cultures expressed low levels of CD25, and showed a diminished Granzyme B expression compared to that of the untreated MLC, suggesting that these cells may not be fully functional. An array of cytokines in the MLC supernatant was analyzed, and IL-5 and IL-13 were significantly reduced by OKT3 or hOKT3gamma1(Ala-Ala) treatment. These results demonstrated that OKT3 and hOKT3gamma1(Ala-Ala) have similar effects on T cells in MLC. Both antibodies inhibited the logarithmic expansion of allo-reactive T cells, probably through inducing suboptimal proliferation of specific and non-specific T cells. This in vitro study provided one possible mechanism of the therapeutic effects of OKT3 and hOKT3gamma1(Ala-Ala) antibodies.
authors.affiliation: Centocor, Inc. 200 Great Valley Parkway, Malvern, PA 19355, USA. spopma@cntus.jnj.com
authors.forename: Sicco H
authors.initials: SH
authors.lastname: Popma
authors.forename: Don E
authors.initials: DE
authors.lastname: Griswold
authors.forename: Li
authors.initials: L
authors.lastname: Li
mesh_terms: D061067:Antibodies, Monoclonal, Humanized; D017252:CD3 Complex / Q000276:immunology*; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D004151:Dipeptides / Q000737:chemistry; D005434:Flow Cytometry; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects; D007959:Lymphocyte Culture Test, Mixed; D016853:Muromonab-CD3 / Q000737:chemistry / Q000494:pharmacology*; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects*
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D017252:CD3 Complex; D016207:Cytokines; D004151:Dipeptides; D007166:Immunosuppressive Agents; D016853:Muromonab-CD3; D015375:Receptors, Interleukin-2; C002956:alanylalanine; C502540:teplizumab