The immediate-type skin reaction and the emetic response in unsensitized monkeys on challenge with staphylococcal enterotoxin B (SEB) were studied to define the role of cysteinyl leukotrienes (LTs) in the action of the toxin. LY 171883, a selective LTD₄/LTE₄ receptor inhibitor, antagonized SEB-induced skin reactions and emetic responses completely. Inhibition of prostanoid formation by indomethacin, however, and pretreatment with BW755C, a dual lipoxygenase and cyclooxygenase inhibitor, did not influence these reactions. The generation of endogenous cysteinyl LTs upon intragastric SEB administration was established in vivo. There was a tenfold increase in LTE₄, the major biliary cysteinyl LT, and a novel cysteinyl LT metabolite in urine occurred, indicating strongly enhanced LT generation on SEB challenge. These results provide the first evidence that cysteinyl LTs may be important mediators in the pathophysiology of SEB-induced effects, as a model for pseudo-allergic reactions.

The primary phase of nephrotoxic serum nephritis produced by rabbit nephrotoxic serum appears to be dependent to a great extent, but not completely, upon the participation of serum complement. On the other hand, duck nephrotoxic serum produces its primary renal injury without detectable utilization of or dependence upon serum complement. The secondary phase of nephrotoxic serum nephritis appears to be largely or entirely dependent upon the host's antibody response to the heterologous gamma globulin fixed in the glomeruli. No evidence could be obtained for the existence of an autoimmune antikidney response by the host in this experimental model.

The staphylococcal enterotoxin serotype B (SEB)-induced enteric intoxication and the immediate-type reaction in the skin of unsensitized monkeys was used to define whether agents competing with SEB for target cell receptors may inhibit pathophysiological effects. For this purpose a duodenal provocation test was developed by use of a pediatric gastroscope, allowing the evaluation of the influence of antagonists on the intestinal disorder upon SEB challenge at the same duodenal site. First, carboxymethylation of histidine residues of SEB caused a complete loss of emetic and skinsensitizing activity without changing the immunological specificity. However, carboxymethylated SEB is a strong inhibitor of enteric intoxications and immediate-type skin reactions upon SEB challenge. Second, after immunization of BALB/c mice with monoclonal anti-SEB antibodies, monoclonal antiidiotypic antibodies (anti-Id) were obtained by the "hybridoma technique" and purification by idiotype-affinity chromatography. Anti-Id specifically inhibited the binding of horseradish peroxidase-labeled anti-SEB to the ligand, and SEB blocked as well the interaction of these two antibody species, indicating a high degree of binding-site selectivity. Anti-Id completely protected against emetic response and diarrhea upon duodenal provocation with SEB and inhibited immediate-type skin reactions as well. Further, anti-Id acted as an antagonist without triggering biologic functions themselves. This shows that anti-Id constitute a useful tool to protect against a bacterial toxininduced intestinal disorder.Staphylococcal enterotoxins (SE) are responsible for one of the most common types of food poisoning in humans (1). All SE produce emesis and diarrhea in humans and other primates as a result of oral administration, whereas the toxin appears to have little, if any, clinical effect in other laboratory animals (1). Although considerable efforts have been expended on attempts to define the pathogenesis, so far very little information has been available on the mode and cellular site of SE action in the gastrointestinal tract.Recently, however, evidence was provided that unsensitized monkeys develop an immediate-type reaction in the skin upon intradermal challenge with SE serotype B (SEB; ref.2). As shown by a series of experiments, SEB administered intradermally causes skin reactions by affecting mast cells (2). This type of nonimmunological mast cell stimulation by SEB offered a new approach, providing a model for investigating the mechanisms of SEB action. In addition, evidence was provided that carboxymethylation of SEB resulted in a loss of toxicity associated with the complete abrogation of skin-sensitizing activity without changing the immunological specificity of the toxin. It has been established that carboxymethylated SEB (CM-SEB) could compete with SEB for binding sites on the target-cell surface (2). To define whether SEB exerts its effect on mast cells by binding to specific celt-surface receptors or whether a less specific type of ligand-...

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