Fig 4. Parasite-specific Ab production is reduced and delayed in Icos^-/- mice after re-challenge.

Splenocytes isolated from WT and Icos^-/- mice isolated before re-challenge (day 92) and post-challenge (days 5, 9, and 35) were used to determine the number of parasite-specific IgM (A, B) and IgG (C, D) ASCs by ELISpot [P. c. chabaudi AMA-1 (A, C) and MSP-1₄₂ (B, D)]. Serum AMA-1 (E) and MSP-1₄₂ (F) specific IgG endpoint titers were determined by ELISA. Normalized absorbance of AMA-1 (G) and MSP-1₄₂–specific (H) IgG at day 35 p.c. as determined by ELISA. The x-axis (log2) displays increasing molar concentrations of NH₄SCN. A nonlinear regression curve fit is shown; the intersection of the dotted line at the normalized absorbance of 0.5 with the curves represents the concentration of NH₄SCN needed to elute 50% of the bound IgG off the Ag. Data are representative of two independent experiments with at least three mice per group (error bars, s.e.m.). An aligned rank transformation was performed on non-parametric data before determining significance by two-way ANOVA with a post hoc Holm-Sidak’s multiple comparisons test. * p < 0.05, ** p < 0.01, **** p ≤ 0.0001, NS not significant.