Abstract

AIMS: To investigate the relation between the numbers of interphase silver stained nucleolar organiser regions (AgNORs) and immunolabelling with the monoclonal antibody PC10, which demonstrates proliferating nuclei by reacting with proliferating cell nuclear antigen (PCNA). METHODS: The established sequential technique for the demonstration of interphase AgNORs and of antigens in paraffin wax sections was applied to a small series of non-Hodgkin's lymphomas (NHL) of both low and high grade type, together with specimens of palatine tonsil. The numbers of PCNA positive cells were counted in all specimens; in the tonsils the cells were counted in both follicle centres and in the interfollicular areas. The numbers of AgNORs in both PCNA positive and PCNA negative nuclei were then counted. RESULTS: Lower numbers of PCNA positive cells were found in the low grade than the high grade NHL (18-28.4% and 34.2-51.3%, respectively). This was reflected in the two areas of the palatine tonsils, the counts being higher in the follicle centre nuclei than in those in the interfollicular compartments. In general, the numbers of AgNORs were higher in the PCNA positive nuclei than in those lacking the antigen; however, a consistent finding was that relatively high AgNOR scores were observed in PCNA negative nuclei, especially in the high grade lymphomas. In the tonsils, however, the AgNOR counts were much lower in the nuclei lacking PCNA than in those containing it. CONCLUSIONS: The results obtained in the lymphomas were rather unexpected as, in general, previous studies have shown a close direct or indirect relation between AgNOR scores and proliferating cell counts. An explanation for these findings may be that the argyrophil proteins associated with proliferating cells remain in the nucleus in detectable form longer than the PCNA antigen, at least in neoplastic tissue.