CD4 and malaria: Again, we observed a decreased proportion of IFN-γ-producing cells for both the total pool of antigen-experienced T cells (CD44+) (Fig 3D) and among all CD4 T cells (Fig 3E). Together, these data suggest that active malaria parasite infection reduces the ability of memory CD4 T cells to produce IFN-γ in response to both stimulation via the T cell receptor (TCR) and to non-specific stimulation of TCR signaling pathways by PMA/iono treatment.