Mitogenic activity of the outer membrane of Treponema denticola

The outer membrane (OM) was isolated by detergent extraction from Treponema denticola ATCC 35405, ATCC 33521 and ATCC 35404, representing serovars a, b and c, respectively, as well as from two fresh isolates of T. denticola. Strict precautions were undertaken against the introduction of contaminant lipopolysaccharide when the OM was isolated. The OM was active in mitogenic stimulation of C3H/HeOuJ mouse spleen cultures, but to a somewhat lesser extent than purified lipopolysaccharide (LPS) from Escherichia coli 055:B5. Polymyxin B only partially inhibited the response. Unheated OM abrogated mitogenic activity of E. coli LPS, but heated preparations enhanced the mitogenic activity of E. coli LPS, suggesting the presence of a heat-labile cytolytic factor associated with T: denticola OM in addition to a putative lipopolysaccharide and/or heat-stable lipoprotein.