Increased cationic fluxes in stimulated lymphocytes of the mouse: response of enriched B- and T-cell subpopulations to B- and T-cell mitogens

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Abstract
Suspensions of mouse (Balb/c) splenic lymphocytes took up the K congener 86Rb at a net rate (calculated as K+) of 4.6 .+-. 0.2 f[femto]mol cell-1 h-1 before stimulation with the mitogen concanavalin (Con A) and of 8.5 .+-. 0.4 fmol cell-1 h-1 after stimulation. These net transport rates were of similar magnitude to those previously reported in the case of resting and stimulated human peripheral blood lymphocytes. One difference between the mouse and human systems was the increased transport noted within minutes of stimulation, in the case of the latter that required 6 h before becoming evident in the former. When similar transport studies were performed using splenic lymphocytes of the homozygous congenitally athymic nude mouse, Con A, a T cell mitogen, caused neither a blastogenic response (operationally defined as increased uptake of labeled thymidine into DNA after 48 h culture in presence of mitogen) nor the increase in cation influx; [Escherichia coli] lipopolysaccharide (LPS), a B cell mitogen, caused increased transport and blastogenesis. As it has been shown that both mitogens bind equally well to B cells and to T cells, it follows that the increased cation pumping characteristic of activated lymphocytes is not caused by the binding of mitogen per se, but is a consequence of the proliferative response. Attempts to demonstrate the same correspondence between B and T cell specificity of mitogen and increased cation fluxes in Balb/c [mouse] splenic lymphocytes purified by the wheat germ agglutinin (WGA) technique yielded equivocal results. The T cell enriched population, although greatly purified as judged by membrane markers (fluorescent goat antimouse Ig staining), showed no purification with respect to enhanced cation influx and little or none with respect to the incorporation of labeled thymidine induced by Con A. This mitogen also induced increased Rb+ transport and thymidine incorporation in a subpopulation enriched for B cells by the WGA technique. 86Rb efflux from Con A treated, unfractionated Balb/c splenocytes rose after stimulation to a rate 40% higher than that from resting cells. This observed imbalance between the magnitude of increase in influx (100%) and efflux probably could account for the increased number of K ions required to be transported into the cell water, in order that concentration of this ion be kept constant during the enormous expansion of cell volume characteristic of blastogenesis.