Partial biochemical characterization of spiroplasma membrane component inducing tumor necrosis factor alpha

We have recently found that membranes of Spiroplasma spp. strain MQ-1 (hereafter referred to as MQ-1) induce both tumor necrosis factor alpha (TNF alpha) secretion by bone marrow macrophages and blast transformation of lymphocytes via a mechanism different from that operated by bacterial lipopolysaccharide (LPS). This report presents evidence indicating that the MQ-1-derived membrane component(s) which activates bone marrow macrophages to secrete TNF alpha is, at least in part, protein. This conclusion is supported by our findings that TNF alpha secretion was reduced following exposure of MQ-1 membranes to elevated temperatures, extreme acidic pH treatment and incubation with protease K or pronase. Furthermore, following lipid extraction of MQ-1 membranes, most of both induction of TNF alpha secretion and blast transformation activities appeared in the 'protein' fraction. When membranes were chromatographed on a phenyl-Sepharose column, two major peaks were obtained, one containing most of the TNF alpha induction activity and the other the mitogenic activity. Neither peak coeluted with the peak of bulk membrane lipids. The possibility that the spiroplasma membrane component inducing TNF alpha secretion is acylated protein is discussed.