Effector pathways regulating T cell activation

Activation of T lymphocytes is a key event for an efficient response of the immune system. It requires the involvement of the T cell receptor antigen as well as costimulatory molecules such as CD28. Engagement of these recept ors through the interaction with a foreign antigen associated with major hi stocompatibility complex molecules and CD28 counter-receptors B7.1/B7.2, re spectively, results in a series of signaling cascades acting in synergy and which culminate in activation of interleukin-2 gene transcription and even tually cell proliferation. Many studies aimed at characterizing these speci fic effector pathways have been published; however, the actual signaling mo lecules that transduce activation signals from the cell membrane to the nuc leus and that directly regulate interleukin-2 gene transcription are not ye t completely defined and remain a matter of debate. In this commentary, we have attempted to analyze the results, which are sometimes diverging if not totally contradictory, characterizing effector pathways that possibly are triggered during T cell activation. (C) 1998 Elsevier Science Inc.