Volume regulation by human lymphocytes. Identification of differences between the two major lymphocyte subpopulations.

Following exposure to hypotonic media, human peripheral blood lymphocytes swell initially but restore their isotonic volume within minutes. In contrast, tonsillar lymphocytes demonstrate a similar initial phase of swelling but fail to restore their isotonic volume. We have studied the ionic basis for this second or regulatory volume decrease (RVD) phase using lymphocytes from peripheral blood, tonsil, and thymus. RVD was characterized by 86Rb efflux and a decrease in K+ content. The increase in K+ permeability in response to hypotonic challenge was characteristic for T lymphocytes obtained from peripheral blood, tonsil, or thymus. B lymphocytes showed only a modest increase in K+ permeability and consequently little RVD. The data confirm that the response of peripheral blood and tonsillar lymphocytes to a hypotonic environment can be accounted for by differences in the proportions of T and B cells, and the differential behaviour of B and T lymphocytes is based on differences in membrane permeability to K+ upon swelling.