FIG. 4.

Purified B-1a cells from uninfected and schistosome-infected mice mediate apoptosis of purified CD4⁺ T cells. Splenocytes from mice infected for 8 weeks were cultured in media for 24 h and then were enriched for CD4⁺ T cells by magnetic bead depletion of CD19⁺ B cells and CD8⁺ T cells. CD4⁺-T-cell targets were then cultured without added cells (black bar) or mixed at the indicated ratios with B-cell subsets purified from freshly isolated splenocytes of uninfected mice and mice infected for 8 weeks. After 24 h of coculture, the cells were stained with anti-CD4-PE, annexin V-FITC, and PI and were analyzed by three-color flow cytometry. The viable CD4⁺ T cells (CD4⁺/PI⁻) were gated and analyzed for binding of the early apoptosis marker, annexin V. The percentages were normalized by arcsine transformation prior to determination of means and standard deviations. Reverse transformed means ± standard deviations of quadruplicate samples from a representative of three experiments are presented.