Adaptive Immunity, Autophagy Figure 6. Autophagy-deficient mice are susceptible to cerebral and ocular toxoplasmosis. Becn1+/2 and littermate control mice (B6) were infected with ME49 T. gondii. A, Survival was monitored daily. Data shown are from groups containing 8 mice. B, Mice (5 mice per group) were euthanized at 4 weeks post-infection. DNA was isolated from eyes and the levels of the T. gondii B1 gene were examined using real time quantitative PCR. Tissue cysts were counted in brain homogenates. C, Eyes from infected control mice revealed mild histopathology. D, E, Eyes from infected Becn1+/2 mice revealed disruption of retinal architecture, more prominent inflammation and invasion of the retina by retinal pigmented epithelial cells (E). PASH; X200. F, Brains from infected control mice showed slight inflammation. G, Brains from infected Becn1+/2 mice show prominent areas of inflammation (arrow) and frequent tissue cysts (arrow head). PASH X100. H, Levels of IFN-c, TNF-a and NOS2 mRNA in eyes and brains were examined using real time quantitative PCR and normalized against the levels of 18s rRNA. Each group contained 5 mice. I, Beclin 1 and actin protein expression in primary microglia from control and Becn1+/2 mice. Primary brain microglia from control and Becn1+/2 mice and were incubated with anti-CD40 or control mAb, or with IFN-c/TNF-a followed by infection with tachyzoites of RH T. gondii. Primary bone marrow derived macrophages were obtained from control and Becn1+/2 mice and were incubated with or without rapamycin (1 mM) 2 h after infection with tachyzoites of RH T. gondii. Results are shown as the mean 6 SEM and are representative of 3 independent experiments. **p#0.01. doi:10.1371/journal.pone.0014472.g006 work contrasts to studies in IFN-c-activated cells. In marked distinction to IFN-c, CD40 induces toxoplasmacidal activity independently of Irga6 as well as Irgm1 and Irgm3 [33]. Importantly, deficiency of Beclin 1 or Atg7 blocked CD40-induced killing of T. gondii while leaving unaffected killing induced by IFN-c. The different mechanisms used by CD40 and IFN-c to kill T. gondii likely explain the cooperation observed between CD40 and IFN-c to promote control of the parasite both in vitro [34,35] as well as in vivo (this study). Indeed, while IFN-c, TNF-a and NOS2 are key for resistance against chronic toxoplasmosis, we report that the PLoS ONE | www.plosone.org 9 December 2010 | Volume 5 | Issue 12 | e14472