Hyperosmolarity selectively enhances IgE-receptor-mediated histamine release from human basophils

Abstract

Increased osmotic pressure has been reported to cause non-cytotoxic histamine release (HR) from human basophils, as well as a potentiation of HR induced by anti-IgE. In this study, the effects of hyperosmolar Na-K-acetate (300-600 mOsm/kg H2O) on HR was studied in washed human blood cells from newborns, adult volunteers and patients with severe atopic dermatitis. These three patient groups represented 3 very distinct populations with respect to total plasma IgE content, medians were less than 0.2 IU/ml, 20.5 IU/ml and 2508 IU/ml; respectively. Increasing osmolarity to 500 mOsm/kg H2O caused little HR in the absence of other stimuli, whereas at 600 mOsm/kg H2O a significant increase in spontaneous HR was seen. The HR induced by anti-IgE and Concanavalin A, acting through the IgE-receptor, was increased approximately twofold at 500 mOsm/kg H2O. Responses were highly correlated to results at 300 mOsm/kg H2O. The use of 600 mOsm/kg H2O buffers caused a further increase in most, but not all blood samples. The potentiation of IgE-receptor-mediated HR when using hyperosmolar media was clearly independent of plasma IgE contents, and did not change the concentration-response to anti-IgE. In contrast, HR induced by the IgE-receptor-independent stimuli, Formyl-met-leu-phe and calcium ionophore A 23187, were not enhanced at all by increased osmotic pressure. We conclude, that hyperosomolar media selectively enhance IgE-receptor-mediated HR. The use of hyperosmolar media may therefore be beneficial in a diagnostic application of washed blood HR assays used in allergy diagnosis.

Elementary immunology: Na+ as a regulator of immunity

“…Increases in Na + concentration by 40 mM, comparable to levels found in infected or dietary Na + -laden skin, did not interfere with ROS production of N -formyl-methionyl-leucyl-phenylalanine (fMLP)-activated granulocytes and even enhanced the elastase release of fMLP-activated granulocytes [99, 100]. Similarly, enhancing osmolarity with Na + /K + acetate augmented the release of histamine from basophil granulocytes [101]. Whether increased salt concentrations, as found in infected and inflamed skin tissue, affect the subcellular charge balance of phagosomes is as yet unknown (reviewed in [102]).…”

Histamine releasing cells of the newborn

“…Washed blood cell preparations were made as described in detail previously, as were the normo-and hyper-osmolar Na-K-acetate buffers (300 mOsmAg H2O and 500 mOsm/kg H.O. respectively) (11). A microfibre-based fluorometric histamine release assay was employed, as described previously (10).…”

“…Concomitantly, the effects of hyperosmolarity were studied. Hyperosmolarity was found to increase IgE-mediated release of histamine (11). and due to mechanistic similarities between the actions of phorbol ester and hyperosmolarity, a common mechanism of action has been suggested (26).…”

Immune responses to nematode exoantigens: sensitizing antibodies and basophil histamine release

“…HR was determined by a microfiber-based method in washed blood cells, as previously described (21,26,28). Briefly, blood samples were washed four times in a Na-K-acetate buffer before resuspension in the original volume.…”

“…Previous experiments have shown that the use of a hypertonic Na-K-acetate bufler in HR experiments increased the sensitivity of the HR assay without distorting the concentration responses to IgEmediated stimuli (21). Eor study of the effects of the hypertonic buffer on antigen-induced HR, blood samples from the first 61 consecutive patients were prepared in 500 mOsm/kg H2O buffer (232 mM Naacetate), and 58 blood samples were prepared in a buffer containing 140 mM of Na-acetate(300 mOsm/ kg H3O).…”