The genetic basis of natural susceptibility to progressiveCryptococcus neoformansinfection is not well understood. Using C57BL/6 and CBA/J inbred mice, we previously identified three chromosomal regions associated withC. neoformanssusceptibility (Cnes1,Cnes2, andCnes3). To validate and characterize the role ofCnes2during the host response, we constructed a congenic strain on the C57BL/6 background (B6.CBA-Cnes2). Phenotypic analysis of B6.CBA-Cnes2mice 35 days afterC. neoformansinfection showed a significant reduction of fungal burden in the lungs and spleen with higher pulmonary expression of gamma interferon (IFN-γ) and interleukin-12 (IL-12), lower expression of IL-4, IL-5, and IL-13, and an absence of airway epithelial mucus production compared to that in C57BL/6 mice. Multiparameter flow cytometry of infected lungs also showed a significantly higher number of neutrophils, exudate macrophages, CD11b+dendritic cells, and CD4+cells in B6.CBA-Cnes2than in C57BL/6 mice. The activation state of recruited macrophages and dendritic cells was also significantly increased in B6.CBA-Cnes2mice. Taken together, these findings demonstrate that theCnes2interval is a potent regulator of host defense, immune responsiveness, and differential Th1/Th2 polarization followingC. neoformansinfection.