Cover legend. Vol. 196, No. 6, September 16, 2002.

The cover picture legend for the September 16 issue cited the incorrect related article. The full legend, with correct attribution, appears below. Please note, the legend appears correctly online.

Absence of the splenic marginal zone in mice lacking the p110d subunit of phosphatidylinositol 3-kinase. Mutant mice lacking p110d reveal that this enzyme is responsible for the bulk of phosphatidylinositol 3,4,5-trisphosphate produced in response to B cell receptor (BCR) ligation. These mice have severely reduced B1 and marginal zone (MZ) B cell populations but apparently normal development of follicular B cells. p110d-deficient mice respond poorly to immunization with carbohydrate and protein antigens and fail to generate a germinal center reaction. P110d function is also required for BCR-mediated activation of Btk, PLCg2, and calcium flux. Immunofluorescent staining was performed on splenic cryosections using MOMA-1(green) and anti-IgM (red) and revealed a marked reduction in MZ B cells in p110d−/− mice (right panel). See related article by Clayton et al., pages 753–763.