Activation of Lymphocytes by Lymphokines

The identification, cloning, and expression of the genes for lymphokines and their receptors have provided insight into their structure. Identification of the regulatory regions within the genome is also allowing the characterization of the processes that control the expression of these genes. The cloning of the receptor genes has so far provided little insight into how the lymphokine signal is transmitted across the cell membrane and eventually to the nucleus. Resting lymphocytes do not express significant numbers of high-affinity receptors for lymphokines. Following the activation of antigen receptors, cells are induced to express high-affinity receptors for an array of lymphokines. The eventual response is determined by the interaction of the lymphokines with their specific receptors on the surface of target cells. The response of the individual cell is determined by its particular pattern of lymphokine receptor expression and by its intracellular machinery. Because several different lymphokines can induce similar responses in a single cell, some lymphokine receptors may signal cells through conserved pathways.