DIFFERENTIAL EXPRESSION OF APOPTOSIS, BCL-X AND C-MYC IN NORMAL AND MALIGNANT LYMPHOID-TISSUES

Bcl-x and c-Myc have an important role for the immune response by regu lating the programmed cell death (apoptosis) of lymphocytes. Dysfuncti on of these selection processes can lead to the development of maligna nt lymphoma. The present study aimed at defining the differential expr ession of apoptosis, Bcl-x and c-Myc in normal and in malignant lympho id tissues. Follicular centre lymphoma (FCL-F) and mantle cell lymphom a (MCL) contained the lowest apoptotic indices (AIs). whereas Burkitt' s lymphoma (BL) had the highest AIs. The AIs correlated ;significantly with the growth rates of the tumours and with the extent of Bcl-x exp ression, Bcl-x was expressed in almost: all BL cells, but in few tumou r cells in FCL-F and in MCL. c-Myc, in contrast, was found in the majo rity of the tumour cells in FCL-F and in MCL, but not in BL. Whereas t he extent of Bcl-x expression correlated positively with the growth ra tes, an inverse correlation was observed between the percentages of c- Myc-positive tumour cells and the growth rates of the tumours. We conc lude that normal and malignant lymphoid tissues have a distinct patter n of apoptosis and that expression of Bcl-x and c-Myc in B cell lympho ma is differentially regulated.