Figure 2.
CD4+ Tfr cells are important for antigen-specific plasma cell and antibody responses following influenza virus infection. (A) Left: Representative image from ELISPOT of HA-specific IgG ASCs. Right: Quantification of HA+ ASCs and total bone marrow cells of Bcl6f/f or Bcl6f/f Foxp3-Cre mice at day 38 p.i. Scale bar, 3 mm. (B) ELISA analysis of serum influenza-specific antibody titers in Tfr cell–deficient (Bcl6f/f Foxp3-Cre) and wild-type (Bcl6f/f) mice at various time points following infection with PR8. At day 15 p.i. (top) and day 36 p.i. (bottom), HA-specific IgG in sera from two groups of mice were quantified by ELISA. (C) Representative plots of quantification of HA-specific IgG1 (left) and HA-specific IgG2a (right) from Bcl6f/f Foxp3-Cre and control mice. (D) Representative plot of NA-specific IgG. (E) Affinity measurements of Bcl6f/f or Bcl6f/f Foxp3-Cre mice at day 36 p.i. determined by 7 M urea ELISA, expressed as percentage of IgG bound to HA treated by 7 M urea divided by untreated IgG bound. (F) The concentration of total IgG in the sera from Tfr cell–deficient (Bcl6f/f Foxp3-Cre) and wild-type (Bcl6f/f) mice at day 36 p.i. Statistical analyses were performed using the unpaired two-tailed Student’s t test (*, P < 0.05; **, P < 0.01). Data for A are pooled from two experiments representative of four or five experiments with four to six mice per group performed day 38 p.i. with PR8. Data for B–D and F are from one experiment representative of three experiments with five to eight mice per group. Data for E are pooled from two independent experiments with four to six mice per group. AUC, area under the curve; BM, bone marrow; n.s., not significant.