ABSTRACT
The induction of an immune response against a particular agent involves multiple interactions between macrophages (which process and present antigens to lymphocytes), helper and suppressor lymphocytes (which amplify and diminish, respectively, the magnitude of the response), and effector lymphocytes. Several investigators have shown that decreased proliferative responses observed in lymphocytes from aged individuals are associated with defects in intracellular signaling mechanisms. Proust et al. have studied protein kinase C activity and translocation, PI hydrolysis, and cytoplasmic Ca2 plus or minus levels in lymphocytes from aged individuals in order to determine if changes in these intracellular signaling mechanisms are associated with decreased proliferative responses. The ability of lymphocytes to proliferate in response to mitogenic stimulation depends on the ability of these cells to become activated to both secrete and respond to IL-2. It appears that a number of intracellular signaling mechanisms are set in motion following stimulation with mitogen, including PIP2 hydrolysis with generation of IP3 and diacylglycerol.
