Significance of cerebrospinal fluid adenosine deaminase isoenzymes in tuberculous (TB) meningitis

Adenosine deaminase (ADA) exists as two isoenzymes, ADA(1) and ADA(2). It a ppears that the ADA(2) isoenzyme originates mainly from monocytes and macro phages. In tuberculous pleural effusions most of the ADA activity consists of ADA(2). The aim of this prospective study was to analyse ADA isoenzymes in the CSF of patients with meningitis to investigate whether the expected rise of the ADA(2) isoenzyme would occur in tuberculous meningitis. ADA iso enzyme analysis was performed on the CSF of 15 patients with tuberculous an d 11 patients with bacterial meningitis by an automated kinetic enzyme coup led assay in the presence and absence of a specific ADA inhibitor. The rati o of ADA(2)/ADA(Total) was >0.8 in 14/15 patients with tuberculous meningit is. In bacterial meningitis the ratio was less than or equal to0.8 in 10/11 patients. The ADA(2) isoenzyme is the major contributor to increased ADA a ctivity in the CSF of patients with tuberculous meningitis, probably reflec ting the monocyte-macrophage origin of the ADA. (C) 2001 Wiley-Liss, Inc.