T and B lymphocytes express receptors for antigen on their cell surface. These receptors perform a sensory function, recognizing and binding non-self antigens complexed with proteins encoded within the major histocompatability complex (MHC). When these receptors are stimulated they relay this information to the interior of the lymphocyte through a complex series of events known as signal transduction. Signal transduction can take many forms and these forms, or pathways, are shared by many different cell types. One mechanism that lymphocytes use to relay information from the receptor to the nucleus is through enzymes known as kinases and phosphatases. Another mechanism involves the flux of ions across the cell membrane. The information relayed by these different pathways results in a specific response by the lymphocyte to its environment. These responses include proliferation, the inability to respond (anergy), or even programmed cell death. Defects or inadequacies in the molecular machinery involved in transmission of signals from the lymphocyte membrane to the nucleus are linked to cellular transformation and the inability of the immune system to respond appropriately. The emphasis of our laboratory is to understand the mechanisms by which signals that arise at the cellular membrane are relayed to the interior of the cell. Our research also focuses on the interactions between signaling pathways. To accomplish these objectives we are currently using protein chemistry, molecular biology, and tissue culture. Understanding and identifying the specific events that occur during signal transduction will aid our understanding of how these pathways are integrated, regulated, and function. This will help in the identification or treatment of different pathologies resulting from alterations in these pathways.