P53, RB AND BCL-2 EXPRESSION DURING THE CELL-CYCLE - A STUDY IN PHYTOHEMAGGLUTININ-STIMULATED LYMPHOCYTES AND MICROWAVE IRRADIATED LYMPHOID-TISSUE SECTIONS

Aims-To determine the expression of p53, Rb, and bcl-2 during the cell cycle in stimulated peripheral blood lymphocytes (PBLs) and microwave heated reactive lymphoid tissue sections. Methods-The expression of p 53, Rb and bcl-2 proteins in paraffin wax embedded tonsil tissue secti ons was detected by immunohistochemistry using an (APAAP) technique fo llowing microwave irradiation. Flow cytometric analysis as performed o n phytohaemagglutinin (PHA) stimulated PBLs, with simultaneous S fract ion determination. Results-Expression of p53 protein was detected in r eactive tonsil germinal centre cells, in some suprabasal cells in the surface and cryptic epithelium, and in some endothelial cells. Analysi s of p53 in PHA stimulated PBLs revealed expression of p53 by non-tumo ral activated lymphocytes. Rb protein expression was increased in PHA stimulated PBLs and was usually detected in most germinal centre B cel ls, in isolated paracortical cells, in a fraction of endothelial cells , and in most epithelial suprabasal cells. Expression of bcl-2 in stim ulated lymphocytes was inversely correlated with proliferation, This c onfirms findings in reactive tonsil tissue samples, where proliferatin g cells located in the germinal centres and paracortical area are most ly bcl-2 negative. Conclusions-Expression of these three oncogenic and tumour suppressor proteins varies during the cell cycle in non-tumora l cells. Consequently, tumoral growth fraction must be taken into acco unt when analysing dysregulation of these three genes in lymphomas and other tumours. The p53 protein may be detected in benign conditions, as its expression is not synonymous with malignancy or mutation of the p53 gene.