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 ε chain of CD3 that is recognized by the mAb, 145-2C11 (2C11 mAb); one clone also expressed the V(β)8 epitope of the α/β 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 μM 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.
|Original language||English (US)|
|Number of pages||9|
|Journal||Journal of Immunology|
|State||Published - Jan 1 1989|
ASJC Scopus subject areas
- Immunology and Allergy