CTLA4 and malaria: The blockade of the co-inhibitory receptors CTLA-4, PD-1, Tim-3 and/or LAG-3 leads to an enhancement of the pro-inflammatory T cell responses and a more severe course of disease in murine malaria models, but can also improve parasite clearance, indicating the double-edged role of CD4+ T cells in malaria13,14,16,17.