Based on our earlier data on the enhancing effect of histamine on the action of interleukin-6 (IL-6), we have studied the molecular mechanisms of these interactions. The effect of histamine was investigated on the binding of 125I-IL-6 by B lymphoma cell line CESS, monocytoid cell line U937 and hepatoma cell line HepG2. Histamine increases the IL-6 binding by CESS cells and inhibits that by U937 and HepG2 cells. Using H1 receptor (cetirizin and loderix) and H2 receptor (cimetidine and ranitidine) specific antagonists, an H1-dependent stimulation of IL-6 binding by CESS cells was found. In contrast, down-regulation of IL-6 binding by histamine was clearly mediated through H2 receptors. On U937 cells, using a monoclonal antibody reacting with the 80 kd chain of the human IL-6 receptor, and H2-receptor mediated inhibition of IL-6 receptor expression was found by FACS analysis.
The occurrence and composition of complexed beta2-microglobulin (beta2m) in sera and synovial fluids of rheumatoid arthritis and systemic lupus erythematosus patients and control persons was investigated. Beta2m-containing complexes were detected in immune complex (IC)-enriched fractions isolated by precipitation with 3% polyethylene glycol 6000, in the macromolecular peaks after Sephadex G-200 gel filtration, and in IC desorbed from solid-phase Clq. Beta2m complexes were demonstrated also after precipitation of redissolved PEG-insoluble material by anti-human beta2m serum or isolation of the complexes by use of Sephadex-anti-beta2m. IgG was co-isolated with beta2m on Sephadex-anti-beta2m and free beta2m inhibited the binding of IgG to Sephadex anti-beta2m, indicating that IgG was present in the complexed beta2m. Analysis by SDS-polyacrylamide gradient electrophoresis under reducing conditions indicated that the purified beta2m complexes contained IgG and beta2m.
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