Figure 4. Therapeutic ligation of OX40 during acute Plasmodium infection enhanced both Th1- and Tfh-like recall responses and per cell protective capacity of memory CD4 T cells.
(A) Experimental design. Mice were infected with 1×106 Py and administered either control rIgG or α-OX40 antibodies on day 7 and 10 p.i. On 75 day p.i., memory CD4 T cells were sorted and transferred (2×105) into groups of Tcrα−/− mice. Recipients were challenged with P. yoelii and parasite growth kinetics were measured. Cells were analyzed on day 14 p.i.
(B,C) Kinetics of parasite growth (B) and summary data (C) showing parasitemia on day 14 p.i. Statistical analyses (*p < 0.05) reflect comparisons between recipients of memory cells from rIgG- and α-OX40-treated donor mice.
(D-F) Proportions of donor-derived CD4 T cells expressing either Ly6C (D), IFN-γ (D,E), or CXCR5+PD1+ Tfh cells expressing Bcl-6 (F).
(G) Total number of CXCR5+PD1+Bcl-6+ Tfh cells recovered from recipients.
(H) MSP119-specific serum antibody titers in mice seeded with memory CD4 T cells derived from rIgG- and α-OX40-treated donors.
Data (Mean +/− SEM) in (B,C,E,G,H) are pooled from 2 independent experiments with 3–4 mice/group per experiment and were analyzed using either one-way ANOVA (B,C) or Student’s t tests (E,G,H). *p<0.05 **p<0.01. N.S. = not significant. See also Figure S4.