Fighting Tb Might Be a Matter of ‘flipping a Switch’ in Immune Response

In the lung, alternatively activated macrophages (AAM) form the first line of defense against microbial infection. Due to the noninflammatory nature of AAM, the lung can be considered as an immunosuppressive organ for respiratory pathogens. However, as infection progresses in the lung, another population of macrophages, known as classically activated macrophages (CAM) enters. CAM are far more effective than AAM in clearing the microbial load, producing pro-inflammatory cytokines and anti-microbial defense mechanisms necessary to mount an adequate immune response. Because AAM have been classified as non-inflammatory macrophages, they could be one important cause for the delay in the lung’s protective immune response as reported in the literature. Their research was concerned with determining the first time when the population of CAM becomes more dominant than the population of AAM. This proposed “switching time” may have important implication in vaccine and therapy development.