Human T and B lymphocytes differ morphologically and immunologically although little is known concerning their physiological parameters and biochemical constituents. In this study, microviscosity and lipid composition in normal human B and T lymphocytes were investigated. Microviscosity was examined using 1,6-diphenyl-1,3,5-hexatriene as a probe and lipid composition was analyzed by thin-layer chromatography with flame ionization detection. Microviscosity of T lymphocytes was higher than that of B lymphocytes throughout the temperature ranges tested, and microviscosity of whole lymphocytes was similar to that of B lymphocytes rather than that of T lymphocytes. There was no significant difference in lipid composition between B and T lymphocytes. However, it was postulated that the concentration of lipid per area of plasma membrane in B lymphocytes might be less than that in T lymphocytes. It was concluded that B lymphocytes show a less rigid membrane fluidity than T lymphocytes because of the lower concentration of lipid per area of plasma membrane.
