IL4R and Mycobacterium infection: Previously, it was not known whether the absence of IL-4Rα during mycobacterial infection influences Arg1 and NO expression, and may therefore alter susceptibility to Mtb. Therefore, we investigated the role of IL-4Rα-activated alternative macrophages during Mtb infection using LysMcreIL-4Rα-/lox mice, where the IL-4Rα allele is flanked by loxP sites and the Cre recombinase is under the control of the lysozyme M gene (LysMcre), thus restricting Cre-mediated excision of IL-4Rα in macrophages and neutrophils.