Stimulation with HA triggers B-cell differentiation. Splenic B cells or whole spleen cells were cultured in the presence of HA (0.1 mg/mL) for (a) 24 or (b) 120 hours. The cells were harvested and splenic B cells were stained for the expression of CD44 and whole spleen cells were stained for CD45R using flow cytometry. The two histograms were overlayed for comparison. The mean channel number suggestive of the intensity of fluorescence for the histograms was as follows: CD44 (a) = 13.7, CD44 (b) = 85.9; CD45R (a) = 13.9, CD45R (b) = 7.09.