PLASMA-LEVELS AND IN-VITRO PRODUCTION OF TUMOR-NECROSIS-FACTOR-ALPHA AND INTERLEUKIN-6 IN PATIENTS WITH AMEBIC LIVER-ABSCESS

We studied the plasma levels of tumor necrosis factor-alpha (TNF-alpha ) interleukin-6 (IL-6) as well as the in vitro production of these cyt okines by peripheral blood mononuclear cells, in 10 patients with ameb ic liver abscess (ALA) and seven healthy controls. TNF-alpha was measu red using a bioassay with L929 fibroblasts; IL-6 was quantitated by th e B9 cell line assay. in both assays, the number of viable cells was e stimated by the conversion of MTT to formazan. TNF-alpha plasma levels were nondetectable (<20 pg/mL) in ALA patients, as well as in the maj ority of healthy controls. The in vitro production of TNF induced by l ipopolysaccharide was significantly decreased in ALA patients. Most AL A patients (8/10) had increased plasma levels of IL-6. Furthermore, th e spontaneous production of IL-6 in vitro was significantly increased in ALA patients compared to controls. In the acute stage of the ALA, a negative relationship was found between the raised plasma levels of I L-6 and the in vitro diminished production of TNF-alpha. After recover y, ALA patients showed both normal plasma levels and in vitro producti on of TNF and IL-6. Our data corroborate previous reports regarding pl asma levels of TNF in ALA, and suggest that E. histolytica induces the in vivo production of IL-6 through a TNF-independent pathway. The rai sed levels of IL-6 might in turn down-regulate the production of TNF i n ALA patients.