lipid-a and Lymphoma--B-Cell

Incubation of the mouse B-lymphoma cell line 70Z/3 with bacterial lipopolysaccharide (LPS) results in the secretion of immunoglobulin M (IgM) to the cell surface. We now demonstrate that LPS rapidly induces the tyrosine phosphorylation of a 41 kDa protein in 70Z/3 cells transfected with CD14, a glycosyl phosphatidylinositol-anchored membrane receptor for complexes of LPS and LPS binding protein. There was no indication of LPS-mediated tyrosine phosphorylation in untransfected 70Z/3 cells, which do not express CD14. The 41 kDa tyrosine phosphoprotein was specifically induced by LPS, since it was not observed after incubation with another activator of IgM expression, interferon-gamma. Induction of this 41 kDa phosphoprotein was not observed when the transfected cells were treated with LPS in the absence of serum. Phosphorylation was also blocked by preincubation of the cells with an antibody to CD14. Furthermore, lipid A from Rhodobacter sphaeroides inhibited LPS-mediated tyrosine phosphorylation and surface IgM expression. Expression of CD14 in the LPS-unresponsive mutant 70Z/3 cell line 1.3E2 did not result in the secretion of IgM, although tyrosine phosphorylation was increased after incubation with LPS, suggesting that the mutation in these cells is downstream of the membrane LPS receptor.

Topics: Animals; Antigens, CD; Antigens, Differentiation, Myelomonocytic; Immunoglobulin M; Lipid A; Lipopolysaccharide Receptors; Lipopolysaccharides; Lymphoma, B-Cell; Mice; Phosphorylation; Phosphotyrosine; Protein-Tyrosine Kinases; Receptors, Immunologic; Transfection; Tumor Cells, Cultured; Tyrosine

LPS is the most important antigen of Brucella bacteria which are gram-negative facultative intracellular pathogens infecting a large proportion of animals and humans in the world. In order to get insights into the immune response mechanisms monitored by Brucella, its LPS was used as a model antigen. S-LPS, R-LPS, lipid A and O-chain purified from Brucella abortus were tested in their capacity of inducing SDS-resistant MHC class II molecules after incubation with murine B lymphoma cells. S-LPS and O-chain gave a significant response suggesting that O-chain might induce an association with class II itself or might act as a carrier for antigens to bind MHC class II molecules.

Topics: Animals; Brucella abortus; CD4-Positive T-Lymphocytes; Chickens; Drug Resistance; Female; Histocompatibility Antigens Class II; Hot Temperature; Immunosorbent Techniques; Lipid A; Lipopolysaccharides; Lymphoma, B-Cell; Mice; Mice, Inbred CBA; Muramidase; Sodium Dodecyl Sulfate; T-Lymphocytes, Helper-Inducer; Tumor Cells, Cultured