Nuclear morphology of follicular center cell-associated T-cells: an immunoultrastructural study of follicular hyperplasia and follicular center cell lymphomas.

Although the immunophenotypic nature and distribution of T-cells in normal follicular centers and in follicular center cell lymphomas have been studied in great detail, the morphology of these cells has been largely ignored. Immunoultrastructural studies using UCHT-1, an antibody to the T-cell receptor-associated CD3 antigen, were therefore performed on four tonsils with reactive follicular hyperplasia and on four follicular center cell lymphomas. T-cells present in normal follicular centers had a mean maximum nuclear diameter of 4.9 +/- 0.93 microns and were not significantly different from those associated with neoplastic follicular center cells which had a maximum nuclear diameter of 4.9 +/- 1.2 microns. In contrast, the T-cells in normal interfollicular T-zones had a mean maximum nuclear diameter of only 4.4 +/- 0.81 microns which was significantly smaller than either of the previous two groups (P = 0.002 and P = 0.004, respectively). Similarly, T-cells in a relatively uninvolved T-zone in a follicular center cell lymphoma had a mean maximum nuclear diameter of 4.5 +/- 0.78 microns. The nuclear configuration of the follicular center cell-associated and interfollicular T-cells ranged from round to clefted with the greatest number of clefted T-cells being associated with the follicular center cell lymphomas. These data demonstrate that T-cells associated with either normal or neoplastic follicular center cells tend to be larger than interfollicular T-cells. Because of the very variable nuclear configurations of these T-cells, not all cells with clefted nuclei in follicular centers or follicular center cell lymphomas can be assumed to be of B-cell origin.