Lipopolysaccharide as a tool to reveal autoreactive B cells.

It has been found in several different test systems that LPS is competent to induce autoantibodies of different specificities. As a rule only IgM autoantibodies have been found. The presence of autoreactive B cells in healthy individuals indicate that autoreactive B cells have not been not eliminated by the induction of immunological tolerance. This result is to expected according to the concept of the one non-specific signal hypothesis for B cell activation, which only ascribes a passive focussing role to the immunoglobulin receptors, whereas activation and tolerogenic signals are delivered via non-clonally distributed receptors for polyclonal B cell activators and T cell interleukins. The induction of autoantibodies by LPS in mice does not result in detectable disease or symptoms. Therefore, the ability of LPS to induce IgM autoantibodies does not constitute a model for induction of autoimmune diseases. The main importance of these findings is that the self-non-self distinction is not carried out by B cells. Presumably T cells alone are responsible for the self-non-self distinction.