Hydrolysis of inositol phospholipids induced by stimulation of the T cell antigen receptor complex in antigen-specific, murine helper T cell clones. Requirement for exogenous calcium

• Published in: The Journal of immunology (1950) Vol. 143; no. 2; pp. 587 - 595
• Main Authors: Bonvini, E, DeBell, KE, Kolber, MA, Hoffman, T, Hodes, RJ, Taplits, MS
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 15.07.1989
• Subjects: Animals; Antibodies, Monoclonal - physiology; Antigen-Presenting Cells - immunology; Antigen-Presenting Cells - metabolism; Calcium - pharmacology; Clone Cells - classification; Clone Cells - drug effects; Clone Cells - metabolism; Epitopes - immunology; Hemocyanins - immunology; Hydrolysis; Mice; Mice, Inbred C57BL; Microspheres; Phosphatidylinositols - immunology; Phosphatidylinositols - metabolism; Receptors, Antigen, T-Cell - drug effects; Receptors, Antigen, T-Cell - metabolism; T-Lymphocytes, Helper-Inducer - classification; T-Lymphocytes, Helper-Inducer - drug effects; T-Lymphocytes, Helper-Inducer - metabolism
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.143.2.587

Two murine, keyhole limpet hemocyanin-specific, Th cell clones were studied for their ability to respond to antibody-mediated stimulation of the TCR complex or to Ag-pulsed accessory cells by hydrolyzing inositol phospholipids. Both clones were positive for the determinant expressed on the epsilon chain of CD3 that is recognized by the mAb, 145-2C11 (2C11 mAb); one clone also expressed the V beta 8 epitope of the alpha/beta chains of the TCR recognized by the F23.1 mAb. Treatment of these cells with 2C11 or F23.1 mAb adsorbed onto polystyrene beads induced a time-dependent accumulation of inositol phosphates (IP). Keyhole limpet hemocyanin-pulsed accessory cells which expressed the appropriate MHC phenotype also induced IP accumulation, whereas no response was induced by medium-treated or MHC congenic accessory cells. The hydrolysis of inositol phospholipids induced by TCR perturbation depended upon the presence of exogenous Ca2+; Mg2+ did not substitute for Ca2+. Treatment of cells with ionomycin at concentrations up to 30 microM was unable to induce hydrolysis of inositol phospholipids, indicating that entrance of Ca2+ was itself insufficient to generate IP. Stimulated IP generation was rapidly blocked upon addition of EGTA to the incubation medium. Reducing the level of exogenous Ca2+ decreased the production of inositol mono-, bis-, and trisphosphate isomers similarly, suggesting that extracellular Ca2+ was required for the initiation of the hydrolysis rather than affecting phospholipase C affinity for its substrates. We concluded that activation of inositol phospholipid hydrolysis by perturbation of the TCR complex in the Th cell clones under investigation displays a Ca2+-dependent component which is likely to be proximal to IP generation.