Lastly, while our findings with the Bhlhe40fl/fl-Cd4-cre mice indicate that Bhlhe40 expression in T cells is critical to controlling infection with P. yoelii 17X, this result does not rule out the contribution of Bhlhe40 expression in another cell type to the observed phenotype in the germline knockout mice. The gene discussed is BHLHE40; the disease is infection.