TD antigen-driven GC response in KSHV latency locus transgenic mice. KSHV latency locus transgenic mice and littermate controls were immunized with NP-KLH or PBS (n = 6). After 10 d, splenocytes were subject to fluorescence-activated cell sorter (FACS) analysis. Blood was collected on d 0, 5, 10, and 14. (A) Activated GC (CD19⁺CD71⁺PNAhi) are plotted. (B) Levels of resting non-NP–specific Igs of 9 wild-type (WT; red triangle) and 6 transgenic mice (black circle) were plotted on the first or second column, respectively. * and *** represent significant difference with P < .05 and P < .005 by Student t test, respectively. (C) The frequency of plasma cells was analyzed by FACS. Cells from spleens (SP; n = 5) or BM (n = 6) in WT or latency transgenic mice (TG) were subject to FACS. CD19^- cells were further gated with B220 and CD138. Percentages of CD19^-B220^-CD138⁺ cells among CD19^- lymphocytes are plotted. (D) Representative flow cytometry profiles of plasmablasts (CD19^-B220⁺CD138⁺) and plasma cells (CD19^-B220^-CD138⁺) from FACS analysis in (C) were shown.