A CONTRIBUTION TO THE INCIDENCE OF NUCLEOLI IN NORMAL HUMAN BLOOD MONOCYTES

Background and Objective. Normal blood monocytes were studied in blood donors to provide more information on the presence of nucleoli and nu cleolar types in these cells. Methods. Nucleoli in monocytes were visu alized using cytochemical procedures that detect RNA and characteristi c nucleolar proteins, i.e. nucleophosmin, nucleolin, fibrillarin and A gNOR proteins, in periphral blood smears. Results. Nucleoli were detec ted in all blood monocytes. The nucleolar coefficient (number of nucle oli per cell) was 2.6 and no differences were found between men and wo men. Concerning the incidence of nucleolar types, monocytes from both male and female blood donors possessed mainly only inactive micronucle oli characteristic of mature or advanced maturation stages of blood ce lls; however, 16-20% of monocytes also contained functionally dominant ring-shaped nucleoli, which reflect a reversible decrease of rRNA tra nscription and in blood cells are intermediate stages between actively transcribing large nucleoli in highly immature cells and inactive mic ronucleoli in terminal nucleolated maturation stages. Monocytes contai ning large nucleoli with a relatively uniform distribution of RNA char acteristic of immature or stimulated blood cells were rare (< 2%). Int erpretation and Conclusions. Nucleoli are present in all normal blood monocytes. The incidence of the main nucleolar types represents a very convenient complementary marker for evaluating the maturation and pos sibly the stimulated state of these cells. (C) 1997, Ferrata Storti Fo undation.