Figure 3.

LPS induces Ca²⁺ mobilization in a proportion of B lymphocytes in the normal B cell repertoire. (a) Real-time ratiometric imaging of cytosolic Ca²⁺ levels in B cells pre-loaded with Fura, washed and incubated in Ringer’s solution containing Ca²⁺ (2 mM), and then stimulated with LPS, lipid A, anti–δ mAb/dex or thapsigargin (as indicated by arrow) for up to 20 m (when thapsigargin was used for stimulation, Ca²⁺ was not added until after cells were stimulated for 2 m). Depicted is the trace of ratio of fluorescence intensity at 340 nm over that at 380 nm, as a measurement of the free cytosolic Ca²⁺ level, of up to 10 cells (representative of at least 80 cells analyzed). Each colored trace depicted Ca²⁺ mobilization (above the threshold set as greater than 220% that of background) in an individual cells and black traces depicted cells with no Ca²⁺ mobilization. Data are representative of four independent experiments. (b) Quantification of B cells showing Ca²⁺ mobilization upon stimulation by with LPS, lipid A, anti-δ-mAb/dex or thapsigargin (which blocks Ca²⁺ transport back to ER, thereby raising cytosolic Ca²⁺ levels in all cells). Data are mean and s.d. from triplicates.