Dissociation of phosphoinositide hydrolysis and Ca2+ fluxes from the biological responses of a T-cell hybridoma.
T lymphocytes can be activated in a variety of ways, including occupancy of the T cell antigen receptor (TCR) complex or cross-linking of certain cell-surface molecules with antibody. Two of the earliest events seen after stimulation are the hydrolysis of phosphatidylinositol bisphosphate to inositol trisphosphate (Ins P3) and 1,2-diacylglycerol (DAG), and an increase in the concentration of intracellular Ca2+ ([Ca2+]i). Later, the cell secretes lymphokines and expresses lymphokine receptors. It has been postulated that the products of the hydrolysis of phosphatidylinositols (Ptd Ins) and fluctuations in [Ca2+]i are critical 'second messengers', transmitting the signals for the initiation of the later events. We have examined the relationship between these second messengers and the secretion of IL-2 in a murine T cell variant whose missing TCR complex had been reconstituted by gene transfer. Surprisingly, although the IL-2 responses of the transfectant could not be distinguished from the original line expressing the same TCR, Ptd Ins hydrolysis and the increase in [Ca2+]i were substantially reduced or absent in the reconstituted cell. It is therefore possible to dissociate these early biochemical changes from a late biological response, raising questions about the putative causal relationship of these events.
Sussman
J J
JJ
Division of Cancer Treatment, National Cancer Institute, Bethesda, Maryland.
Merćep
M
M
Saito
T
T
Germain
R N
RN
Bonvini
E
E
Ashwell
J D
JD
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006825:Hybridomas; D006868:Hydrolysis; D007376:Interleukin-2 / Q000378:metabolism; D051379:Mice; D010716:Phosphatidylinositols / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*
D007376:Interleukin-2; D010716:Phosphatidylinositols; D002118:Calcium