Host-pathogen specificity in tuberculosis.

The host response to mycobacterial infection including tuberculosis depends on genetically controlled host and bacterial factors and their interaction. A largely unknown aspect of this interaction is whether disease results from an additive and independent effect of host and pathogen or from specific host-pathogen combinations. The preferential association of specific mycobacterial strains with specific ethnic groups provided tentative evidence in favor of host-pathogen specificity in tuberculosis and is consistent with the hypothesis of host-mycobacterial co-adaptation. Substantial evidence for specificity has now been provided by animal models and human case-control association studies. These studies indicate that differences in the host response to infection are at least in part due to specific combinations of host genetic factors and genetic and phenotypic characteristics of the infecting mycobacterial strain.