Ultrastructure of normal human blood T lymphocyte subsets isolated by cell sorting using monoclonal antibodies

Summary  In continuation of a previous study, the quantitative fine structural characteristics of the average normal human pan-T lymphocyte and its subsets in the peripheral blood has been established using stereological methods. T cell subpopulations were isolated and identified by means of monoclonal T3, T4 and T8 antibodies and a fluorescence-activated cell sorting machine. Comparative studies on ultrastructural morphology were made between the E-rosetting lymphocyte and the T3-positive cell, both markers of the pan-T cell, and between the functionally different T4- and T8-reactive subsets, defining the helper/inducer and suppressor/cytotoxic T cell subpopulation respectively. No significant differences were recorded between the E-rosetting and the T3+ lymphocyte except for minor deviations regarding the surface of the plasma membrane. In comparison with the T4+ lymphocyte, the T8+ cell showed a larger cell volume and cell surface area and decreased nucleo/cytoplasmic volume and surface ratios. The increase in cell size was the result of greater volumes of residual cytoplasm as well as of intracytoplasmic organelles, such as mitochondria, RER, Golgi apparatus and granules, whereas nuclear parameter estimates were concordant. The structural deviations between the T4+ and the T8+ subsets are discussed in the context of their different functional capacity as helper and suppressor/cytotoxic cells.