Glycosylated proteins (GP), isolated from the gliding bacterium Cytophaga johnsonae, possess several biological and immunological properties usually attributed to the lipopolysaccharides (LPS) or endotoxins of gram-negative bacteria. They are able to (a) activate 70Z/3 pre-B cells to synthesize IgM, (b) induce B cells from both LPS-responsive and LPS-defective strains of C3H mice to synthesize non-antigen-specific polyclonal immunoglobulin, (c) induce macrophages to produce tumor necrosis factor (TNF), and (d) modulate the magnitude of the antibody response in the absence of regulatory T cells. This occurs, despite the fact that GP are free of lipid A as well as 2-keto-3-deoxyoctonate, two components that are common to all preparations of bacterial LPS. The ability of lipid A derived from the nontoxic LPS of Rhodopseudomonas sphaeroides to block the ability of toxic LPS - but not GP - to induce TNF by macrophages, suggest that GP and LPS may be acting through different mechanisms and/or cell surface receptors to elicit the effects observed.
