lmmunoelectron microscopic examination of cord blood CD5+ B cells.

In this study, we have categorized cord blood CD5(+) B cells, which were examined using the horseradish peroxidase-colloidal gold double labeling immunoelectron microscopy, into three subtypes based on their morphology and immunohistochemical characteristics. Type 1a cells and type 1b cells (9% and 17% of the CD5(+) B cells, respectively) had few cytoplasmic organelles, a high nuclear/cytoplasmic (N/C) ratio (0.66 +/- 0.03 and 0.58 +/- 0.04, respectively), and a low nuclear contour index (NCI) value (1.56 +/- 0.30 and 1.50 +/- 0.27, respectively), whereas type 2 cells (74% of the CD5(+) B cells) had a low N/C ratio (0.44 +/- 0.11) and a high NCI value (2.05 +/- 0.68). Type 2 cells, which had many cytoplasmic organelles, frequently had several uropod-like processes that bound to the gold particles. The N/C ratios clearly showed that there were significant differences among the three types of CD5(+) B cells (p < 0.01), and between CD5(+) T cells and the three types of CD5(+) B cells (p < 0.05). For the NCI values, only type 1b and type 2 cells showed a significant difference (p < 0.05). These findings suggest that type 1a cells are transformed into type 1b cells, and then into type 2 cells.