Amyloid deposition in granuloma of tuberculosis patients: A pilot study

Abstract

AbstractThe formation of granuloma is one of the characteristic features of tuberculosis. Besides, rise in the concentration of serum amyloid A (SAA) protein is the indicator for chronic inflammation associated with tuberculosis. The predisposition of SAA driven secondary amyloidosis in tuberculosis is well documented. However, SAA derived amyloid onset and deposition start sites are not well chracterised in tuberculosis and other chronic inflammatory conditions. We hypothesized that granuloma could be a potential site for amyloid deposition because of the presence of SAA protein and proteases that cleave SAA into aggregation prone fragments. 150 tuberculosis patients were screened and biopsies were collected from the affected organs of these patients. 20 patients showed eosinophilic hyaline rich deposits within and surrounding granuloma respectively. They were further screened for the presence of amyloid deposits. The hyaline material, upon Congo red staining exhibited characteristic apple green birefringence under polarized light, confirming deposition of amyloid. Further upon immuno histochemical staining with anti-SAA antibody, the amyloid enriched areas showed positive immunoreactivity. In this pilot study, wexx have shown granuloma as a potential site for serum amyloid A derived amyloid deposition in tuberculosis patients. This study would set a stage to expxand the clinical and fundamental research for understanding the mechanism of amyloid formation in granuloma underlying tuberculosis and other chronic inflammatory conditions.