title: T4 cell activation by immobilized phytohemagglutinin: differential capacity to induce IL-2 responsiveness and IL-2 production.
abstract: Soluble mitogens, such as PHA induce accessory cell (AC)-dependent T cell proliferation. One function of the AC is to create a stimulatory matrix. Therefore, experiments were carried out to determine whether PHA immobilized onto microtiter plates could stimulate T cells in the absence of AC. Peripheral blood T4 cells were cultured under limiting dilution conditions with either soluble or immobilized PHA with or without rIL-1 beta, rIL-2, r-TNF-alpha, an anti-CD28 mAb (9.3), or irradiated EBV-transformed B cells as AC. The frequency of proliferating T4 cells was assessed by examining wells microscopically, and the frequency of T4 cells producing IL-2 was assessed by examining the ability of supernatants to support CTLL-2 proliferation. The percentage of T4 cells growing and producing IL-2 was determined by a maximum likelihood procedure. Immobilized, but not soluble, PHA induced a mean of 20.0 +/- 2.6% of T4 cells to grow in the complete absence of AC in medium supplemented with rIL-2. Whereas rIL-1 beta, rTNF-alpha, and 9.3 were unable to support T4 cell growth in the absence of rIL-2, each enhanced the percentage of T4 cells responding to immobilized PHA in the presence of rIL-2. In contrast, both soluble and immobilized PHA were unable to induce T4 cell IL-2 production in the absence of AC, even when cultures were supplemented with rIL-1 beta or 9.3. In the presence of AC, a small percentage of T4 cells (5.4 to 11.7%) was stimulated to produce detectable amounts of IL-2 by either immobilized or soluble PHA. Moreover, in the presence of AC, a very small population (approximately 1%) of PHA-stimulated T4 cells proliferated without supplemental rIL-2. The data indicate that a matrix of immobilized PHA is sufficient for some T4 cells to be activated to respond to IL-2, whereas others require additional signals provided by rIL-1 beta, rTNF alpha, 9.3, or AC. In contrast, neither soluble nor immobilized PHA is sufficient to induce T cell IL-2 production. This response requires signals provided by intact AC.
authors.affiliation: Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235.
authors.forename: J B
authors.initials: JB
authors.lastname: Vine
authors.forename: T D
authors.initials: TD
authors.lastname: Geppert
authors.forename: P E
authors.initials: PE
authors.lastname: Lipsky
mesh_terms: D000328:Adult; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D000938:Antigen-Presenting Cells / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology; D002472:Cell Transformation, Viral; D004357:Drug Synergism; D004854:Herpesvirus 4, Human; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D007376:Interleukin-2 / Q000096:biosynthesis / Q000494:pharmacology*; D008213:Lymphocyte Activation; D010641:Phenotype; D010835:Phytohemagglutinins / Q000494:pharmacology*; D012995:Solubility; D013601:T-Lymphocytes / Q000145:classification / Q000276:immunology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D007375:Interleukin-1; D007376:Interleukin-2; D010835:Phytohemagglutinins; D014409:Tumor Necrosis Factor-alpha; D013755:Tetradecanoylphorbol Acetate