title: Intravenous immunoglobulin G-mediated inhibition of T-cell proliferation reflects an endogenous mechanism by which IgG modulates T-cell activation.
abstract: Commercial intravenous immunoglobulin G (IVIG) at high doses has therapeutic benefit in autoimmune and inflammatory diseases. It has been shown to inhibit T-cell function but the mechanisms are unclear. Inhibition could result from IVIG processing, donor pooling or intrinsic downregulatory activity of IgG. To address these points, we compared the effects on T-cell activation of IVIG, Fab(2) fragment and IgG isolated from single-donor plasma. We also investigated the role of accessory cells in the IVIG effects using highly purified T cells stimulated through CD3 and CD28 engagement. T-cell proliferation was evaluated by Oregon Green 488 dye dilution and (3)H-thymidine incorporation. IVIG, Fab(2) fragment of IVIG and autologous, single-donor IgG significantly inhibited T-cell proliferation (35-50%), even in the absence of accessory cells. Depletion of IgG from plasma used for culture significantly increased (by 50%) the T-cell proliferation. The addition of physiological concentrations of single-donor, autologous IgG or IVIG to IgG-depleted plasma reduced T-cell proliferation to levels observed in normal plasma. Therefore, donor pooling in IVIG and accessory cells are not required for inhibition of T-cell proliferation by IVIG and the Fab(2) region is sufficient to mediate this inhibition. Suppression of T-cell activation by IVIG likely reflects a physiologic, endogenous mechanism of IgG-mediated regulation of T-cell activation.
authors.affiliation: Department of Pathology, Dalhousie University, Nova Scotia, Canada.
authors.forename: Heather F
authors.initials: HF
authors.lastname: MacMillan
authors.forename: Tim
authors.initials: T
authors.lastname: Lee
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Issekutz
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D018106:CD28 Antigens / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D005434:Flow Cytometry; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology / Q000494:pharmacology*; D007074:Immunoglobulin G / Q000276:immunology / Q000494:pharmacology; D016756:Immunoglobulins, Intravenous / Q000737:chemistry / Q000276:immunology / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D018106:CD28 Antigens; D017252:CD3 Complex; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D016756:Immunoglobulins, Intravenous; D011948:Receptors, Antigen, T-Cell