Human--human hybridomas secreting lipid A reactive monoclonal antibodies

Five human-human hybridoma cell lines secreting monoclonal antibodies (mAbs) against lipid A (LA) were produced by cell fusion of Epstein-Barr virus (EBV) transformed human peripheral blood lymphocytes and a human lymphoblastoid cell line KR-4. All these mAbs were isotyped as IgM(kappa) and reacted with lipopolysaccharides (LPS) and LA of various gram-negative bacteria. Whereas the binding of only four of the five mAbs to solid-phase LA was blocked by polymyxin-B sulphate, the mitogenic effect of LPS and LA on murine B lymphocytes was inhibited by all five mAbs. These results demonstrate that the human immune system recognizes at least two common epitopes in lipid A of various gram-negative bacteria.