TB bug inhibits any which way

Each new study of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), seems to come up with a new resistance mechanism, and fails to see evidence for the mechanisms claimed by others. Now Stewart Chang, Jennifer Linderman, and Denise Kirschner (University of Michigan, Ann Arbor, MI) use a mathematical model to conclude that multiple mechanisms operate. Different mechanisms are best suited to protection under different conditions, and some are masked by experimental protocols used in previous studies.Mtb prevents macrophages from doing their job primarily by inhibiting antigen presentation by MHC class II. The Michigan group included four parts of this process (identified by others) that could be inhibited: MHC transcription; MHC protein maturation; antigen processing; and peptide loading onto MHC. IFN-γ and antigen got things going, and surface expression of peptide-loaded...