Figure 4. IL-21 is necessary for TFH cell development.
IL-21+/+, IL-21+/- and IL-21-/- mice (3 mice per group) were immunized subcutaneously with KLH emulsified in CFA. Seven days after the immunization, experimental mice were sacrificed and TFH cells (A) and the germinal center B cells (B) were analyzed. Numbers in dot plot quadrants represent the percentages. Germinal centers were determined by immunohistochemical analysis (C). Spleen cells from immunized mice were stimulated in 96-well plates as triplicates with the indicated concentration of KLH peptide. Proliferation was assayed after 3 days of treatment by adding [3H]thymidine to the culture for the last 8 h. IFN-γ was measured after 4 days of treatment. The experiments were repeated twice with consistent results.