RELEASE OF SOLUBLE TUMOR-NECROSIS-FACTOR RECEPTORS IN MEDITERRANEAN SPOTTED-FEVER RICKETTSIOSIS

Tumor necrosis factor alpha (TNF) is a key cytokine in the defense aga inst many intracellular pathogens, including Rickettsia conorii, the c ausative agent of Mediterranean spotted fever (MSF). The levels of two soluble TNF receptors (sTNFR-p55 and sTNFR-p75), the extracellular do mains of the two cell surface receptors for TNF, were elevated in the acute-stage plasma samples from 20 patients with serologically confirm ed MSF. The median values were 3.1 and 7.8 ng/ml for sTNFR-p55 and sTN FR-p75, respectively. sTNFR values correlated significantly with plasm a TNF concentrations. Patients with severe MSF had higher values for b oth receptor fragments than patients with nonsevere disease. The diffe rences were statistically significant for sTNFR-p55 (median, 5.8 versu s 2.0 ng/ml; P = 0.008), Given the proportionately higher values for b oth TNF and sTNFR-p55 in patients with severe MSF, the sTNFR-p55/TNF r atios for the two patient subgroups did not differ (P = 0.5), while th e sTNFR-p75/TNF ratios were significantly different (P = 0.01), with d isproportionately lower values in patients with severe disease.