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Notes: The histamine-releasing capability of lipopolysaccharides (LPS) was examined in human leukocyte suspensions. LPS alone did not release histamine, but was found to enhance the histamine release caused by anti-IgE. Also the IgE-mediated histamine release caused by specific antigens (allergens or bacteria) in sensitized individuals was enhanced by LPS. The potentiating effect of LPS was observed in grass pollen and dog dander allergic patients as well as in patients sensitized to E. coli or Staph, aureus bacteria. No potentiation was obtained by exposure to unspecific allergens or bacteria to which the persons were not sensitized. Bacteria can release histamine by immunological or nonimmunological mechanisms, and only the immunological histamine release was found to be potentiated by LPS. It is speculated that endotoxins reinforce release of histamine caused by allergens in allergic patients or by bacteria in persons sensitized to these microorganisms.

Notes: To study the human intestinal mast cell of children and adults, we combined a sensitive glassfibre-based histamine assay with the enzymatic and mechanical dispersion of surgical specimens or mucosal biopsies. The method yields between 1.2 × 103 to 4.6 × 103 mast cells/mg tissue constituting 1.2% to 5.3% of total cell count. The mast cell yield, however, depends on the intestinal tissue specimen used for dispersion. Aliquots containing 1500 mast cells per sample are sufficient for measuring significant amounts of histamine (± 0.15 ng histamine per sample), thus making it possible, to carry out approximately 75 tests for four mucosal biopsies of 10 mg each. The intestinal mast cell releases histamine in a dose-dependent manner on challenge with anti-IgE (6–600 U/ml), ionophore A23187 (0.25–1.0 μM), and Concanavalin A (0.7–25.0 μg/ml). The histamine release shows interindividual variation with a net histamine release between 0 to 2.5 ng/samples dependent on the secretatogue. In general, it is not necessary to passively sensitize the mast cells to obtain a sufficient histamine release response to anti-IgE challenge, indicating the presence of intact and functional cell-bound IgE. However, it is shown that four of 10 non-atopic intestinal mast cell samples could be passively sensitized with human plasma containing either mite- or grass-specific IgE without stripping off the IgE first. This indicates the presence of free and preserved Fc-receptors on the dispersed mast cells in some subjects. In addition, it is found that the phorbolester TPA increases the histamine release response to A23187 and turns anti-IgE non-responding mast cells into responding mast cells, but TPA alone at 2 to 16 ng/ml has no histamine releasing effect. In patients with anti-IgE responding mast cells no additional effect of TPA is seen. Finally, no substantial differences between mast cells of children and adults are demonstrated.

Notes: Type I allergy against some common microorganisms was investigated in 14 patients with AIDS and 11 human immunodeficiency virus (HIV) antibody-positive homosexual men, and in a control group consisting of 13 heterosexual men without HIV antibodies. Basophil histamine release technique was used as a sensitive method to detect type I allergy against Candida albicans (CA), Herpes simplex virus type I (HSV-I) and cytomegalovirus (CMV). Of the 14 AIDS patients 11 (78%) showed significant histamine release when stimulated with CA, and HSV-I caused release in 10 (71 %), whereas no response was obtained by CMV. In the group of HIV antibody-positive men only one released histamine when stimulated with CA and HSV-I and this patient also had lymphadenopathia. In contrast to these results, no release of histamine was obtained in the control group consisting of 13 heterosexual men. The histamine release caused by CA and HSV-I is mediated by an immunological reaction, since the release was abolished and regained by removal from and refixation to the cell surface of the cell-bound immunoglobulins. These results suggest an involvement of type I allergy as a pathogenetic co-factor in some infections in AIDS, and allergic type I reactions to CA and HSV-I might be an indicator for the presence of manifest AIDS.

Notes: Basophil histamine release was examined in 26 children suspected of having cow milk allergy (CMA). Following oral challenge with cow milk, the initial adverse reaction reappeared in 20 children, the majority developing urticaria. The urticaria patients showed a high degree of correlation between the results of histamine test, RAST and skin test. Children with gastrointestinal symptoms reacted to milk challenge, but only a few showed a positive histamine test, RAST and skin test. Among the patients with atopic dermatitis, the tests gave mostly negative results, which was in accordance with the lack of response to a milk challenge. The results obtained by removal from and fixation to the cell surface of IgE indicate an IgE-mediated reaction in CMA, which, in connection with the correlation between histamine test and RAST or skin lest, suggests basophil histamine release as a suitable method for testing Type I allergy in children suspected of CMA.

Notes: A new microfibre method for allergy testing measuring histamine release from human basophil leukocytes is described. Samples of 50 μl washed blood are challenged with the suspected allergens. Released histamine is bound to microfibres and measured by a spectrofluorometrical method after removal of interfering substances by washing. The microfibre method (HR-MM) was compared to the conventional histamine release assay using the Ficoll-Hypaque gradient method (HR-FH) in 19 allergic children tested with one of three allergens. In addition, a comparison was made between the microfibre method and in vivo provocation tests, i.e. skin prick test (SPT), bronchial provocation test (BPT) and allergen specific serum IgE (RAST). It was found that the same individuals responded with histamine release to the same allergens in both histamine release assays, and the dose-response curves were almost identical. A positive correlation was found between the in vivo and in vitro tests. Thus it is concluded that the new method can provide reproducible, analytically precise (at the nanogram level) histamine release results in pediatric cases where: 1) a positive SPT does not correlate with case history; 2) BPT may be considered too hazardous or inconvenient; 3) confirmation of negative or inconclusive SPT or RAST is needed. In contrast to other histamine release assays it is a convenient diagnostic tool in children since only small amounts of blood are needed and at least 96 tests can be carried out in 21/2 h

Notes: Since N-acetylneuraminic acid (NANA) in cell membrane glucocalyx mediates or modulates a variety of actions, such as mediator release, we examined a possible modulating role of this amino sugar in histamine release from human basophil leukocytes. Removal of NANA from the cell membrane by the enzyme neuraminidase caused a dose-dependent histamine release. Removal of smaller amounts of NANA enhanced histamine release induced by anti-IgE, Concanavalin A and the calcium ionophore A231B7, and reduced the interval between addition of antigen and initiation of histamine release. Pretreatment with free NANA had the opposite effects, i.e. a diminished and delayed maximal histamine release. The hypothesis that NANA in the cell membrane modulates the cellular response to stimulation was further substantiated by demonstrating that the altered response was reflected by a change in the sensitivity by the cell to extracellular calcium, NANA in the cell membrane glucocalyx thus seems to modulate the basophil response to stimulation by modulating transmembrancous calcium transport.

Notes: The in vitro histamine release response of human intestinal mast cells and basophils challenged with anti-IgE, Concanavalin A, ionophore A23187 and food extracts was compared with skin prick test, RAST analysis and open food challenge. It was not possible to perform food challenge in all patients; however, seven children underwent open food challenge and in five the clinical diagnosis of “true” food allergy was confirmed. The intestinal mast cells were pooled from enzymatically dispersed duodenal biopsies obtained by duodenoscopy from 15 selected children suspected of food allergy, and five age-matched controls. In nine of 10 patients classified as “food allergic” intestinal mast cells released histamine to various food extracts in a dose-dependent fashion. From the mast cells of the nine food-allergic patients compared with non-allergics, the anti-IgE mediated mast cell histamine release was increased. Additionally, at 1000 U/ml anti-IgE the mast cell histamine release was increased compared with their corresponding basophils. However, in non-allergic subjects the histamine release of basophils was increased compared with their corresponding mast cells. Histamine release from basophils was positively correlated to the test scores of the RAST analysis, skin prick test, and food challenge. No apparent correlation between tests scores obtained from histamine release of intestinal mast cell and the other tests was demonstrated, except in children with diarrhoea as only symptom. However, the study gives evidence that duodenal mast cells actually are sensitized with specific IgE and thus may play a pathophysiological role in food hypersensitivity. In addition, the study shows that the ability of different stimuli, including food extracts, to trigger basophil histamine release does not correlate with their potency to induce histamine release from mast cells.

Notes: AIDS patients in contrast to healthy individuals show basophil histamine release by stimulation in vitro of their blood leukocytes with Candida albicans (CA) and Herpes simplex virus Type I (HSV-I). Passive sensitization of cells from healthy individuals with the patient serum or surface immunoglobulins (Ig) derived from leukocytes of AIDS patients caused histamine release by the following stimulation of the cells with CA or HSV-I. When IgE was removed from the surface Ig no response was obtained, whereas a removal of IgG did not diminish the response. In contrast, no passive sensitization was obtained by serum derived from healthy individuals. The results show that IgE is responsible for the histamine release caused by CA and HSV-I in AIDS patients.

Notes: The interrelation of in vitro IgE-mediated parameters, i.e. serum-specific IgE (RAST), basophil cell-bound specific IgE, and histamine release from basophil leucocytes was investigated in a 1-year placebo-controlled, double-blind Cladosporium immunotherapy study involving 22 adult asthmatics. The intense and early burst (within 6 weeks of immunotherapy) of serum-specific IgE did not result in a corresponding increased binding of specific IgE molecules to basophils. Cell-bound IgE increased in the Cladosporium season in both groups at the same time as serum levels of specific IgE declined in the Cladosporium group. In the placebo group histamine release from circulating basophils paralleled changes in basophil-bound IgE. In Cladosporium-treated patients, histamine release cell sensitivity after a lag phase (during immunotherapy dose-increase) declined two log steps, i.e. the cells became less responding in spite of a significant increase in cell-bound IgE. To further evaluate the sensitizing capacity of circulating specific IgE, passive sensitization studies were performed using basophils from a single donor. Although sera taken at the maximal IgE-response showed an enhanced capacity of passive sensitization, the ratio between RAST and passive sensitization capacity increased significantly in Cladosporium-treated patients, implying a less than expected sensitization capacity of immunotherapy-induced specific IgE. The lack of active binding of IgE to basophils might be explained by a reduced Fc-affinity of immunotherapy-induced IgE in contrast to the Cladosporium seasonally induced IgE. Regarding the decrease in histamine release in Cladosporium-treated patients in spite of an increased amount of cell-bound specific IgE, immunotherapy may initiate a decrease in mediator releasibility which is not caused by a reduction in the number of Fc-receptors but rather some yet unknown subcellular mechanisms regulating the histamine release. The described changes in IgE-mediated parameters do not seem to be caused by interference with either specific IgG, or IgG4. Changes in histamine release in the Cladosporium, season were the only IgE-mediated parameter significantly related to the graded clinical efficacy of immunotherapy.