ICOS and infection: We have previously reported the presence of hybrid Th1/Tfh cells expressing both Tfh markers (CXCR5, ICOS, BTLA, IL-21, and Bcl6) and Th1 markers (CXCR3, IFN-γ, T-bet), as well as the regulatory cytokine IL-10 within effector T cells (CD4+CD44hiCD127-) in P. chabaudi infection on day 7 post-infection (p.i.)(Carpio et al., 2015).