Endocytosis of aggregated immunoglobulin G by rat basophilic leukemia cells; rate, extent, and effects on the endocytosis of immunoglobulin E

Rat basophilic leukemia (RBL) cells have distinct receptors for IgE and IgG. We assessed the endocytosis of chemically and immunochemically cross-linked mouse-IgG and its influence on the simultaneous endocytosis of IgE. We found that at 37 degrees C, aggregates of IgG and IgE were endocytosed at about the same rate with one-half of the maximal endocytosis occurring in 5 to 13 min, and the efficiency of endocytosis for both ligands ranging from 40 to 70%. We also found that endocytosis of cross-linked IgE and IgG occurred simultaneously and neither ligand significantly affected the rate or extent of endocytosis of the other. The cells accumulated the cross-linked IgG, and then released it to the extracellular environment, at a rate (less than 3%/hr) slower than the released endocytosed IgE (greater than 10%/hr). Using an assay that discriminates between unbound and receptor-bound oligomeric IgG, we found that oligomeric IgG is endocytosed with its receptor, and that the bulk of the ligand remains bound to its receptor for greater than 120 min after endocytosis. The differences in the rate of release of endocytosed IgG vs IgE suggests that the intracellular fate or pathway of these two oligomeric ligands may differ.     

Characterization of histaminergic receptors in the urinary bladder of sheep

The effect of histamine was studied simultaneously on isolated smooth muscle preparations obtained from the body and base of the bladder of sheep. The histamine had a contractile effect mediated specifically through H1 receptors. It appears that the effect of histamine is not mediated through either a cholinergic or an adrenergic mechanism.     

Porins and lipopolysaccharide of Escherichia coli ATCC 25922 and isogenic rough mutants

Abstract The lipopolysaccharide and porin profile of Escherichia coli ATCC 25922, a smooth strain commonly used in antibiotic susceptibility testing, and five isogenic rough mutants was examined. The lipopolysaccharide of the parent strain had the characteristic ladder pattern on polyacrylamide gels, while that of the mutants appeared similar to chemotypes Ra and Rc of Salmonella typhimurium with some changes in chemical composition. Of the porins, OmpC appeared markedly reduced in the parent strain while OmpF appeared markedly reduced in the mutants. In addition, a new outer-membrane protein of size intermediate to that of OmpC and OmpF was detected in all mutants. Neither parent nor mutants were susceptible to the LPS core-specific P1 phage or the porin-specific PA2 and K20 phages.