B cell ICAMs are required for competitive GC and plasmablast formation in a T cell–dependent immune response. (A) Representative flow cytometric analysis and quantification of IC-1/2^+/+ and IC-1/2^−/− B1-8^hi B cells in GCs of recipient mice 14 d after immunization with NP-OVA. Data are pooled from two independent experiments with a total of 11 mice per group. (B) Analysis of the GC compartment as in A, in MD4 host mice, 7 d after immunization. Data are pooled from two independent experiments with a total of five mice per group. (C) Representative flow cytometric analysis of activated B cells in WT hosts 3 d after adoptive cell transfer and immunization with NP-Ficoll. Data are pooled from two independent experiments with a total of nine mice per group. (D) Flow cytometric analysis of adoptively transferred B cells in the CD138⁺ B220^med plasmablast compartment. Data are pooled from two independent experiments with a total of 10 mice per group. (E) Percentages of B cell subsets within the GC compartment in NP-OVA immunized mice to which either IC-1/2^+/+ or IC-1/2^−/− B1-8^hi B cells were transferred. Data are pooled from two independent experiments with a total of seven to 11 mice per group. Each dot in the graphs represents a single mouse; lines represent the mean. ***, P < 0.0004; ns, not significant; two-tailed Student’s t test.