Interaction of Mycobacterium tuberculosis with human respiratory mucosa

Endobronchial infection is associated with pulmonary tuberculosis in the majority of cases. We have investigated the adherence of Mycobacterium tuberculosis to the human respiratory mucosa.

Organ cultures constructed with human tissue were infected with M. tuberculosis in the presence or absence of mycobacterial fibronectin attachment cell surface proteins and examined by scanning electron microscopy.

M. tuberculosis adhered mainly to extracellular matrix (ECM) in areas of mucosal damage, but not to ciliated mucosa, intact extruded cells, basement membrane or collagen fibres. Bacteria also adhered to fibrous but not globular mucus and occasionally to healthy unciliated mucosa, open tight junctions and to extruded cells that had degenerated, exposing their contents. There was a significant reduction (p<0.05) in the number of bacteria adhering to ECM after pre-incubation of bacteria with fibronectin and after pre-incubation of the tissue with M. avium fibronectin attachment protein (FAP) and M. bovis antigen 85B protein, in a concentration dependent manner. The combined effect of FAP and antigen 85B protein was significantly greater than either protein alone. Bacterial adherence to fibrous mucus was not influenced by fibronectin.

We conclude that M. tuberculosis adheres to ECM in areas of mucosal damage at least in part via FAP and antigen 85B protein.