In contrast to peripheral blood mononuclear cells (PBMC), human thymocytes do not exhibit a proliferative response to the T cell mitogens phytohaemagglutinin (PHA), concanavalin A (Con A), or Staphylococcal protein A (SPA). In thymocytes and PBMC, Con A and PHA induce increases in free cytosolic calcium concentrations ([Ca2+](i)). Since both Con A and PHA induce similar increases in [Ca2+](i) in thymocytes and PBMC, the absence of thymocyte proliferation was not due to an inability to induce an increase in [Ca2+](i). The lack of a proliferative response was secondary to the failure of the mitogens to induce interleukin 2 (IL-2) production. Incubation of mitogen-treated thymocytes with phorbol esters reconstituted IL-2 production and the proliferative response indicating that the cells were indeed activated by the mitogens. Similarly, addition of exogenous recombinant IL-2 also induced mitogen-treated thymocytes to proliferate. This IL-2-dependent proliferation established that SPA, Con A, and PHA triggered the expression of biologically active IL-2 receptors. Since an increase in [Ca2+](i) is a prerequisite, and possibly a trigger, for IL-2 production, the failure of PHA, Con A, or SPA to result in thymocyte proliferation may be due to an inability of thymocytes to respond to increases in [Ca2+ ](i) with subsequent IL-2 production.
|Original language||English (US)|
|Number of pages||11|
|Journal||Clinical and Experimental Immunology|
|State||Published - Jan 1 1986|
ASJC Scopus subject areas
- Immunology and Allergy