CD4 and infection: Further, splenocytes of vaccinated/bi mice, in response to challenge infection, exhibited a strong increase in T. cruzi-specific IFNγ+ or TNFα+ (2.0–3.1-fold) and IFNγ+TNFα+ (4.3–7.8-fold) CD4+ and CD8+ T cells, that were also Ki67+ with effector (CD44+CD62L-) phenotype (compare Fig 5C–5F with Fig 4C–4F, p<0.05–0.01).