Significance of Fas and Fas ligand in tuberculous lymphadenitis.

The Fas/Fas-ligand (FasL) system plays an important role in regulation of apoptosis and the immune response, and is exploited by mycobacteria to evade the immune response. This study was performed to investigate the distribution and levels of FasL and Fas in lymph node granulomas and sera of tuberculous lymphadenitis patients by immunohistochemistry and enzyme-linked immunosorbent assay. The validity of soluble Fas (sFas) or soluble FasL (sFasL) as a diagnostic tool was also examined. Levels of sFasL in serum were elevated among patients. The numbers of FasL stained cells in lymph node granulomas were higher than Fas. Children had significantly higher levels of sFasL as compared to adults. The human immunodeficiency virus (HIV)-tuberculosis (TB)-coinfected patients displayed no differences in the levels of sFasL or sFas compared with HIV-negative patients. The healthy controls from a high endemic tuberculosis country (having latent TB) had significantly higher levels of sFasL than from a country with no TB transmission. The sensitivity and specificity of the FasL and Fas test were low when compared with the culture results as the gold standard. However, by using histology as the gold standard, the sensitivity and specificity of the FasL test were increased to 66.7% and 100%, respectively, but for the Fas test remained low. In conclusion, sFasL and sFas cannot be used as diagnostic tests for tuberculous lymphadenitis. However, its utility in detecting latent TB and childhood tuberculous lymphadenitis remains to be evaluated. FasL seems to play a role in immune modulation and pathogenesis of TB. Modulators of Fas/FasL-mediated apoptosis may therefore be clinically useful.