Fig. 3.

CD4⁺ invariant natural killer T (iNK T) lymphocytes enhance the proliferation of the memory B cell compartment. Purified 5(6)-carboxyfluoresceine diacetate succinimidyl ester (CFSE)-labelled CD19⁺ B cells were preincubated with α-galactosylceramide (α-GC) and co-cultured with CD4⁺ or iNK T-depleted CD4⁺ cells for 8–10 days. Data are means ± s.e.m. from four experiments. (a) Frequency of CD27⁺ cells among CD19⁺ lymphocytes before and after culture. The increase of CD27⁺ cell frequency along culture depends on CD4⁺ iNK T cells. (b, c) Proliferation of memory B cells depends on CD4⁺ iNK T cells. Proliferation of gated CD19⁺ B cells was analysed on day 10 according to CD27 expression and to dilution of CFSE staining. Dot plots show percentages of cells in each quadrant, and absolute number of dividing memory (CD27⁺) cells (CFSE dilution ≥ 1 division) are shown between brackets.