TNF-alpha Production by Peripheral Blood Monocytes in Multiple Sclerosis Patients and Healthy Controls

Background: Aberrant immune responses are evident in the pathogenesis of multiple sclerosis (MS) and it has been proposed that the spectrum of cytokines influence disease outcomes. Leptin and lipopolysaccharide (LPS) of Gram-negative bacteria are both potent cellular stimulators for production of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha). The aim of this study was to compare the TNF-alpha production by peripheral blood monocytes from MS patients with healthy controls. Methods: Peripheral blood samples were stimulated with LPS or leptin. After blocking the Golgi apparatus, intracellular cytokine production was assessed using a monoclonal antibody against human TNF-alpha by the flow cytometry technique. Moreover, plasma level measurement of cytokines was performed using enzyme-linked immunosorbent assay (ELISA). Results: Intracellular levels of TNF-alpha were 16.80 +/- 8.21 and 16.52 +/- 8.23 in MS patients and healthy controls which showed no statistically significant difference between them (p = 0.850). Leptin-stimulated and LPS-stimulated TNF-alpha production showed no significant difference between MS patients and the control group (p = 0.263 and p = 0.191, respectively). However, after treatment with leptin, a weak significant difference was shown between cases and control group (p = 0.049). There were significant differences between cases and controls regarding serum levels of IL-6 and Toll-like receptor-4 (TLR-4) before and after stimulation with leptin and LPS, separately (p<0.05). Conclusion: Taken together, we cannot definitely conclude that TNF-alpha does not play an important role in pathogenesis of MS. However, other characteristics of monocyte activation such as IL-6 or TLRs can elucidate implication of peripheral blood monocytes in MS pathogenesis.