Reduced numbers and frequency of vaccine-induced T_FH in <i>L. sigmodontis</i>-infected mice.

<p>Six- to eight-week-old BALB/c mice were naturally infected with <i>L. sigmodontis</i> or left non-infected and vaccinated with 30 µg DNP-KLH/Alum s.c. at day 60 p.i. PopLN cells derived from DNP-KLH-vaccinated non-infected (white bars) and <i>L. sigmodontis</i>-infected (black bars) mice were stained for CD4, CD44, PD1, CXCR5, ICOS and Foxp3 at day 14 post vaccination. <b>(A)</b> Gating strategy of T_FH. <b>(B)</b> Frequency of CD4⁺ T cells (n = 20; pooled data derived from four independent experiments). <b>(C)</b> Frequencies and total cell numbers of PD1⁺CXCR5⁺ T_FH cells within the CD4⁺CD44⁺ activated T helper cells (n = 14; pooled data derived from three independent experiments). <b>(D)</b> ICOS expression of PD1⁺CXCR5⁺ T_FH cells within the CD4⁺CD44⁺ activated T helper cells (n = 10; pooled data derived from two independent experiments). <b>(E)</b> Foxp3 expression of PD1⁺CXCR5⁺ T_FH cells within the CD4⁺CD44⁺ activated T helper cells (n = 5; data from one experiment representative for two independent repeats). Asterisks indicate significant differences between non-infected and infected mice (student's t-test).