title: The induction of T cell unresponsiveness by rapidly modulating CD3.
abstract: The immunomodulatory effects of an IgM anti-CD3 mAb (38.1) were investigated. 38.1 was distinct from other anti-CD3 mAb, in that it was rapidly modulated from the cell surface in the absence of a secondary antibody. Although 38.1 induced an immediate increase in intracellular free calcium [Ca2+]i by highly purified T cells, it did not induce entry of the cells into the cell cycle in the absence of accessory cells (AC) or a protein kinase C-activating phorbol ester. Clearing of 38.1 from the surface of AC-depleted T cells, documented both by immunofluorescence and by functional activity, was rapid, with markedly reduced levels of initially bound mAb observed after a 1 to 2 h incubation at 37 degrees C and complete modulation noted after a 5-h incubation. Despite rapid modulation of 38.1, the T cells continued to express substantial amounts of surface CD3, suggesting there is a rapid rate of turnover of CD3 molecules on resting T cells. After modulation of 38.1 bound CD3, T cells were markedly inhibited in their capacity to respond to PHA. Inhibition could be overcome by culturing the cells with supplemental AC or IL-2. The inhibitory effects of 38.1 could be mimicked by briefly pulsing cells with the calcium ionophore, ionomycin, that had no effect on surface expression of CD3. 38.1- or ionomycin-pulsed cells were inhibited in their subsequent response to PHA even when exposures were carried out in the presence of EGTA to prevent increases in [Ca2+]i from extracellular sources. Inhibition could not be accounted for by an inability of the ionomycin-treated or 38.1-modulated T cells to increase [Ca2+]i in response to PHA. These studies demonstrate that a state of T cell nonresponsiveness can be induced by modulating CD3 with an anti-CD3 mAb in the absence of co-stimulatory signals. A brief increase in [Ca2+]i resulting from mobilization of internal calcium stores appears to be sufficient to induce this state of T cell nonresponsiveness.
authors.affiliation: Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235.
authors.forename: L S
authors.initials: LS
authors.lastname: Davis
authors.forename: M C
authors.initials: MC
authors.lastname: Wacholtz
authors.forename: P E
authors.initials: PE
authors.lastname: Lipsky
mesh_terms: D000328:Adult; D000911:Antibodies, Monoclonal / Q000378:metabolism; D000938:Antigen-Presenting Cells / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis / Q000276:immunology* / Q000378:metabolism; D001667:Binding, Competitive; D017252:CD3 Complex; D002118:Calcium / Q000378:metabolism / Q000502:physiology; D005110:Extracellular Space / Q000502:physiology; D006801:Humans; D007108:Immune Tolerance / Q000187:drug effects; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D008213:Lymphocyte Activation / Q000187:drug effects; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011948:Receptors, Antigen, T-Cell / Q000032:analysis / Q000276:immunology* / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D007476:Ionophores; D011948:Receptors, Antigen, T-Cell; D015240:Phorbol 12,13-Dibutyrate; D002118:Calcium