Stereologic analysis of the ultrastructure in isolated human T and non-T lymphoid cells

Summary

Leukemic cells from 20 cases of acute lymphoblastic leukemia (ALL), examined for T and B markers and classified according to FAB guidelines, were analyzed by electron microscopy. Using stereologic methods a quantitative morphologic characterization of the average blast, assumed to be of clonal origin and thus representative of the whole population, was obtained within each subset. Comparative studies of the ultrastructure of the T, B and non-T, non-B blast on one hand and of the FAB category LI and L2 on the other were performed. No differences of cell volumes, total cell surface areas, nuclear volumes and surface areas or volumes of nuclear compartments were observed between the immunologically defined subsets. Minor variations were seen in the cellular surface contour, the B blast tending to be more irregular than the T blast. Features most predictive of the immunologic cell type were abundant rough ER in B-derived ALL, increasing with plasmacytoid differentiation, and an increase in dense granules which were often clustered in the vicinity of a well-developed Golgi complex in T ALL. The light microscopic criteria of the FAB classification were nearly all confirmed at the EM-level except that nuclear irregularity was observed to the same degree in both categories. Other differences not related to the FAB scheme were encountered in the volumes of the Golgi complex and of the mitochondrial compartment.

Objective criteria as quantitative estimates of cellular structures may contribute to an improved subclassification in ALL.