SHEAR-STRESS EFFECTS ON HUMAN T-CELL FUNCTION

A modified Couette viscometer was used to study the effect of shear stresses on human T lymphocyte functions. Cell suspensions containing T cells, B cells, and monocytes were subjected to uniform shear stresses of 100 and 200 dynes/cm**2 for 10 minutes. After stress exposure, the T cell response to the lectin phytohemagglutinin-P (PHA-P) was a strong function of the total cell concentration in culture. Stressed cells cultured with 0. 5 mu g/ml PHAP-P at an initial concentration of 1 multiplied by 10**6 cells/ml did not incorporate significant amounts of tritium-labelled thymidine into their DNA. This inability to incorporate thymidine could be related to insignificant amounts of interleukin-2 (IL2) detected in cell culture supernatants. A size analysis revealed that exposure to stress interfered with the ability of PHAP-P to induce cellular enlargement characteristic of an activation response. Fluorescence flow cytometric studies showed that the membrane depolarization response of cell suspensions to PHAP-P was significantly affected after exposure to shear stresses. In contrast, when shear stressed cells were cultured at lower cell densities of 0. 5 multiplied by 10**6 and 0. 25 multiplied by 10**6 cells/ml, the functional responses to PHAP-P were similar to those of controls. The data obtained suggest that controlled exposure to sublytic shear stresses results in alterations that can affect the proliferative response of the T cell population, and that these alterations are cell-density dependent.