Stereological analysis of the ultrastructure in isolated human T and non-T lymphoid cells. I. Description of method and data on normal blood lymphocytes.

Stereological techniques were applied to isolated and purified normal human T and non-T lymphocytes from the peripheral blood, allowing a quantitative characterization of the average cell and its subcellular components in each population at the ultrastructural level. From electron micrographs taken at two levels of magnification and subjected to point counting procedures and measurements on a Kontron Videoplan analyser, absolute and relative data comprising volumes, surfaces and ratios were obtained. The stereological model proved efficient in establishing important differences between the two lymphocyte subsets regarding features generated from the whole cell as well as from the nuclear and cytoplasmic compartments. Thus the average T cell compared to the non-T cell possessed the following qualities: a smaller cell volume and cell surface area due to a smaller cytoplasmic volume and surface area; a lower nuclear euchromatin-heterochromatin volume ratio indicating a greater amount of heterochromatin in the nucleus; a smaller volume and surface area of rough ER, and (to a less extent) a smaller amount of Golgi apparatus, dense bodies and residual cytoplasm. The rare occurrence of parallel tubular arrays were seen in the non-T fraction only, and dense bodies were more often clustered in T cells. The differences are discussed in immunological and functional terms.