Desialylation of T lymphocytes overcomes the monocyte dependency of pokeweed mitogen-induced T-cell activation.
Activation of T lymphocytes by pokeweed mitogen (PWM) is strictly monocyte (Mo)-dependent and results in T-cell mitogenesis and interleukin-2 (IL-2) secretion, coupled with an inability to utilize IL-2 due to an impaired expression of functional IL-2 receptor (IL-2R). Such IL-2R impairment could arise in PWM-activated T cells themselves or, alternatively, be the result of Mo-derived influences, as it is known that PWM binds Mo strongly and does not or poorly binds lymphocytes, and Mo becomes rapidly destroyed in PWM-stimulated cultures of blood mononuclear cells or T cells plus Mo. The present study investigated these possibilities. The results show for the first time that desialylation of T lymphocytes strongly increases their PWM-binding capacity and, in addition, overcomes the Mo requirement for PWM to induce T-cell mitogenesis and IL-2 secretion. Such secreted IL-2 levels were even higher that those found in cultures of Mo-dependent PWM-activated T lymphocytes but similarly to the latter, PWM-activated desialylated purified T lymphocytes exhibited negligible high-affinity IL-2 binding capacity and an inability to utilize the IL-2 they produced. These effects were not due to desialylation itself, as indicated by data obtained with peanut agglutinin, a lectin that becomes strongly reactive with desialylated T lymphocytes. The data clearly indicate the existence of PWM-related events capable of impairing the expression of functional IL-2R without affecting IL-2 secretion, and indicate that such events are due to mechanisms arising at the level of PWM-activated T cells themselves.
Gallart
T
T
Serveì d'Immunologia, Hospital Clinic Universitari de Barcelona, Spain.
Angel de la Fuente
M
M
Josep Barceló
J
J
Alberola-Ila
J
J
Lozano
F
F
D000328:Adult; D001402:B-Lymphocytes / Q000378:metabolism; D018929:Cell Culture Techniques; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007376:Interleukin-2 / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology*; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism; D019158:N-Acetylneuraminic Acid / Q000276:immunology*; D009439:Neuraminidase / Q000494:pharmacology; D011043:Pokeweed Mitogens / Q000276:immunology* / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate
D007376:Interleukin-2; D011043:Pokeweed Mitogens; D009439:Neuraminidase; D019158:N-Acetylneuraminic Acid; D013755:Tetradecanoylphorbol Acetate