Immunohistochemical studies on mycobacteria in tuberculous necrotizing granulomas

Abstract

For the purpose to know the pathogenesis of caseous necrosis in tuberculous lesion, authors compared the presence and the number of mycobacteria in the pulmonary tubercles of various histological types. Forty pulmonary tubercles obtained from 16 patients (9 males, 7 females; mean age 51) were examined. By Ziehl-Neelsen (ZN) method, acid-fast bacilli were detected in 40% of 5 proliferative, in 12.5% of 24 productive and none of 11 sclerotic granulomas. By immunohistological staining with anti-BCG antiserum, positive staining was observed in 60%, 87.5% and 91% of each type of granuloma, respectively. Types of necrosis were classified by silver-staining as necrosis after exudative reactions (EN), necrosis after productive reactions (PN) and filled materials after softening and liquification of necrotic lesions (LN). EN was observed in 24 tubercles, and mycobacteria were stained in 8% of EN by ZN method and in 75% by immunohistological method. PN was observed in 21 tubercles, and mycobacteria were detected in none and 5% of such type of necrosis by respective method. LN was observed in 28 tubercles, and mycobacteria were detected in 11% and 71% of these lesions by respective method. So, positive ratio by immunochemical method was significantly higher in EN and LN than in PN. Further, mycobacteria were stained with anti-BCG antiserum as granules and the number of such granules were much more numerous in EN and LN than in PN (p < 0.01). From these results, it was suggested that necrosis might occur by different mechanisms in exudative reactions and in productive reactions.