HOD alloantibody production occurs in the absence of antigen-specific GC B cells. (A) Representative dot plots used to detect MZ B cells, FO B cells, and GC B cells. (B) Quantification of HEL antigen–specific MZ B cells, FO B cells, or GC B cells on day 3 or 10 following PBS injection or transfusion with HOD RBCs or SRBC^HO. (C) Evaluation of IgM and IgG anti-HOD antibody formation following HOD RBC transfusion at the times indicated posttransfusion. Error bars represent standard deviation; results are representative of 2 independent experiments. ****P < .0001; 1-way ANOVA with Tukey’s post-hoc test. D3, day 3; D10, day 10; ns, not significant.