NORMAL CD5(-LYMPHOCYTES ARE POOR STIMULATORS IN THE AUTOLOGOUS MIXED LYMPHOCYTE-REACTION (AMLR)() B)

The AMLR is decreased in chronic lymphocytic leukaemia (CLL), which is characterized by a monoclonal expansion of CD5(+) B lymphocytes. Sinc e B cells are used to stimulate the AMLR, we investigated the capacity of normal CD5(+) B cells to function as stimulators in the AMLR. We i solated B cells from the peripheral blood of normal individuals and fr actionated them into subpopulations enriched for CD5(+) and CD5(-) cel ls, which were used as stimulators in the AMLR. We found that the CD5( -) B cells were excellent stimulators, whereas stimulation of AMLR by B cells enriched for CD5(+) cells resulted in significantly reduced pr oliferative responses (P < 0.005). This suggests that the reduced AMLR in CLL is due to the predominance of CD5(+) B lymphocytes in the stim ulating cell population.