Peripheral blood CD5⁺ B cells are less calcium responsive than CD5⁻ B cells after BCR activation.

Purified blood B cells were loaded with Fura-2/AM, and the Ca²⁺ response of individual cells to anti-IgM (25 μg/mL) stimulation was performed before anti-CD5 staining. (A) Ca²⁺ levels were analyzed by single cell imaging (right), CD5 expression was revealed by immunofluorescence (middle), and the corresponding transmitted light image (left) of 2 B cells is shown. (B) Individual Ca²⁺ response of the 2 B cells indicated by blue and red arrows. The CD5⁻ cell (red) shows an intracellular Ca²⁺ increase, but the CD5⁺ cell (blue) does not. (C) Occurrence of Ca²⁺ response in CD5⁻and CD5⁺ B cells. Data are from 254 CD⁻ cells and 23 CD5⁺ cells from 3 independent experiments.