To investigate the relationship between cigarette smoking and release of TNF-alpha and its soluble receptors (sTNFRI and sTNFRII) by peripheral blood mononuclear cells (PBMCs) from RA patients.
We studied 71 RA patients with established disease (mean duration 10.6 yr). Smoking history was established by questionnaire. T lymphocytes and monocytes were isolated from peripheral blood and incubated with or without stimulation (phytohaemagglutinin and lipopolysaccharide, respectively). Release of TNF-alpha and sTNFR into culture medium was measured by enzyme-linked immunosorbent assay.
TNF-alpha release by stimulated T lymphocytes was significantly higher in patients with a history of smoking than in those who had never smoked (1416.0 vs 767.4 pg/ml, P = 0.04), and showed a relationship with smoking duration and intensity (P for trend < or =0.009). Monocyte TNF-alpha release was not associated with smoking status. Release of sTNFR showed no clear relationships with extent of smoking, although release by stimulated T lymphocytes was higher in past smokers than in those who had never smoked (P < or = 0.03). The ratio of TNF-alpha/sTNFR released from T lymphocytes was higher in past and current smokers, and was associated with extent of smoking. No relationship was found between smoking and plasma TNF-alpha levels, but levels of both receptors were higher in past smokers.
In RA patients who smoke there is an alteration in the ratio of TNF-alpha/sTNFR released by stimulated T cells that might favour increased TNF-alpha activity. The increased TNF-alpha/sTNFR ratio is associated with extent of smoking, and remains elevated after smoking cessation.