Phenotypic characterization of TdT-positive cells.

Double-staining immunohistochemistry with a TdT-specific antiserum (blue nuclear labeling) and cell surface markers (red staining) shows (A, B, C) coexpression of TdT and CD10 (arrows). C represents the boxed area in B. (D) Double-labeling reveals coexpression of TdT and CD34 in a single cells. Note reactivity of endothelial cells with the CD34 reagent in the top right hand corner. (E, F) Double-staining with TdT- and CD79a-specific antibodies reveals localization of TdT-positive cells outside a germinal center near the dark zone. F represents the boxed area in E at high power. Note that TdT-positive cells are negative for CD79a in this image. (G) This panel illustrates the presence of a few TdT-positive cells coexpressing CD79a. (H) Double-staining with TdT- and CD20-specific antibodies also reveals isolated TdT-positive cells coexpressing CD20.