Microscopic notes on the perinucleolar chromatin region in immature and mature human B-leukemia lymphocytes

Abstract

Perinucleolar region was studied in lymphocytes of patients suffering from chronic B lymphocytic leukemia to provide more information on the perinucleolar-condensed chromatin - heterochromatin - during the maturation of these cells. The perinucleolar heterochromatin of lymphocytes in smear preparations was visualized using a simple, but sensitive cytochemical method for the demonstration of DNA. The perinucleolar heterochromatin was also easily visible as unstained perinucleolar regions in specimens stained for RNA. In addition, the perinucleolar heterochromatin of lymphocytes was distinct and apparent in the transmission electron microscope using conventional as well as cytochemical methods for visualization of chromatin structures. Despite the great variability, the maturation of leukemic lymphocytes was accompanied by an increased width of the perinucleolar heterochromatin shell. It seems to be also interesting that the perinucleolar region of both immature as well as mature leukemia lymphocytes contains heterochromatin bodies about 2µm in diameter. They appeared to be a regular component of the perinucleolar heterochromatin shell and were apparently different from other nuclear bodies present at the nucleolus. In contrary to other known nuclear bodies, perinucleolar heterochromatin bodies in leukemia lymphocytes consisted only of conglomerates of DNA containing chromatin fibrils and did not contain other structural components including RNA. The presence of perinucleolar heterochromatin bodies in the perinucleolar region of leukemia lymphocytes is not contradictory with the present knowledge on that nuclear territory. They might be associated with presumed special perinucleolar DNA loci, which according some previous studies were more expressed in malignant cells.