Staphylococcus aureus peptidoglycan induces histamine release from basophil human leukocytes in vitro

Magnolia officinalis L. bark extract and respiratory diseases: From traditional Chinese medicine to western medicine via network target

The understanding of the use of Magnolia officinalis L. (Magnoliaceae) as a possible dietary supplement for supporting the treatment of airway pathologies might be of clinical interest. Two commercially available bark extracts (M. officinalis extract [MOE]) were characterized by quantitation in honokiol and magnolol content by means of high-performance liquid chromatography with UV detection. MOE effects, as well as those of the reference compounds per se, on some targets connected to airway pathologies (antibacterial- and lung and trachea relaxing- activities) were investigated. Results showed that MOE possessed interesting antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pneumoniae. This was accompanied by a spasmolytic and antispasmodic activity, possibly owing to its ability to concurrently modulate different targets such as H₁ -, β₂ - and muscarinic receptors and l-type calcium channels involved in bronchodilation. All these effects were directly related to the MOE content in honokiol and magnolol. In conclusion, the properties of MOE highlighted here strongly encourage its application as dietary supplement in the treatment of airway diseases.

Combined lifestyle factors, incident cancer, and cancer mortality: a systematic review and meta-analysis of prospective cohort studies

Background

Cancer poses a huge disease burden, which could be reduced by adopting healthy lifestyles mainly composed of healthy diet, body weight, physical activity, limited alcohol consumption, and avoidance of smoking. However, no systematic review has summarised the relations of combined lifestyle factors with cancer morbidity and mortality.

Methods

EMBASE and PubMed were searched up to April 2019. Cohort studies investigating the association of combined lifestyle factors with risks of incident cancer and cancer mortality were selected. Summary hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using random-effects models. Heterogeneity and publication bias tests were conducted.

Results

The HRs (95% CIs) comparing individuals with the healthiest versus the least healthy lifestyles were 0.71 (0.66–0.76; 16 studies with 1.9 million participants) for incident cancer and 0.48 (0.42–0.54; 30 studies with 1.8 million participants) for cancer mortality. Adopting the healthiest lifestyles was also associated with 17 to 58% lower risks of bladder, breast, colon, endometrial, oesophageal, kidney, liver, lung, rectal, and gastric cancer. The relations were largely consistent and significant among participants with different characteristics in the subgroup analyses.

Conclusions

Adopting healthy lifestyles is associated with substantial risk reduction in cancer morbidity and mortality, and thus should be given priority for cancer prevention.

Cell biology of the basophil

The cell biology of basophils, based on published studies spanning 1990-1997, is reviewed. These rarest cells of granulocyte lineages are now available in sufficient numbers for such studies to be done, based on new methods for isolating and purifying the cells from peripheral blood and organ sources and for their derivation in growth factor-containing cultures from their precursors de novo. These studies are dependent on electron microscopy for the accurate identification of basophils, studies which have recently established the presence of basophils in two new species--mice and monkeys. Secretory, endocytotic and storage properties of basophils constitute their mechanistic role(s) in human disease; their role(s) in health is, however, obscure. Development of immunoaffinity and enzyme-affinity ultrastructural labeling techniques to image the Charcot-Leyden crystal protein and histamine in human basophils, coupled with ultrastructural analysis of kinetic samples of cells obtained after stimulation with diverse secretogogues, has provided insight into the role of vesicles in secretory transport mechanisms in human basophils as well as the definition of key ultrastructural phenotypes of secreting basophils.

Purified streptococcal cell wall (PG-APS) causes experimental otitis media

Purified peptidoglycan-polysaccharide from Group A Streptococcus pyogenes cell wall (PG-APS) was prepared under sterile, pyrogen-free conditions and injected percutaneously into the middle ear cavities (MEC) of groups of gerbils. Each group was observed otoscopically at 1, 2, 5, 7, 9, 12 and 14 days. Histologic specimens were obtained from each group at 2, 5, 7, 9 and 14 days. Histologically, PG-APS produced mild, acute inflammation during the first 3 days and mild to moderate inflammation with features of both acute and chronic pathology from days 5 through 9. An early response by plasma cells and macrophages was seen. Most animals had recovered with minor sequelae by day 14. Challenge intraperitoneally with 20 micrograms of PG-APS at 14 days following MEC injection of PG-APS did not exacerbate the middle ear inflammation. Five chinchillas, tested for comparison, responded similarly to PG-APS.

Helicobacter pylori potentiates histamine release from rat serosal mast cells induced by bile acids

In the present study we have experimentally addressed the effects of Helicobacter pylori on the bile acid capability of histamine release. Bile acids alone were confirmed to be able to induce in vitro histamine release from rat serosal and mucosal mast cells. On the contrary, no significant histamine release was obtained when incubating any Helicobacter pylori preparations alone with mast cells. However, histamine release induced by bile acids was significantly enhanced, without any significant increase in lactate dehydrogenase activity, when whole washed or formalin-killed bacterial cells or crude cell walls were incubated with mast cells in the presence of cholic (0.3 mM), deoxycholic (0.3 mM), or lithocholic (0.3 mM) acids, chenodeoxycholylglycine (0.3 mM), and deoxycholyltaurine (3 mM). The electron microscopic features of mast cells incubated with Helicobacter pylori were consistent with an exocytotic secretion. The release of histamine induced by 0.3 mM deoxycholic acid in the presence of Helicobacter pylori was inhibited by the preincubation of the cells with dimaprit (an H2 agonist) and potentiated by the H2 antagonist, ranitidine. The current results suggest a link between human Helicobacter pylori infection and histamine release and a possible involvement of gastric mucosal mast cells in the pathogenesis of Helicobacter pylori-associated gastritis.

Bacteria-induced IgE-mediated histamine release: examination of patients with chronic bronchitis (CB) during acute exacerbations

Twelve patients hospitalized with acute exacerbations of chronic bronchitis (CB) and infected in the lower respiratory tract with H. influenzae (HI) or Streptococcus pneumoniae (SP) were examined. Bacteria, isolated from the expectorate caused an IgE-mediated histamine release from the patient's own blood leukocytes, indicating that all were sensitized to their own bacteria. Sensitization was only observed in some of the patients when tested with a standard panel of HI or SP obtained from other patients, indicating the importance of using the patient relevant bacterial antigenic determinants. No sensitization was found in twelve controls. The patients showed cellular hyperreactivity to HI and SP, i.e. the releasability was higher than in the control group. The cellular hyperreactivity was not dependent on sensitization since it was also found against the non-infecting species. Both sensitization and cellular hyperreactivity may contribute to the aggravation of the disease.

Microorganism-induced or enhanced mediator release: a possible mechanism in organic dust related diseases

Bacteria were found to trigger mediator release, including histamine, leukotriene B4, and prostaglandin D2. Furthermore, histamine release caused by allergens as well as by nonimmunological reactions was enhanced by bacteria, endotoxins, and spores from molds. Mediator release and its enhancement play a crucial role for bronchoconstriction and inflammatory events in the airways. These effects of allergens, microorganisms, and other noxious agents in dusts may, therefore, in concert be responsible for the symptoms in organic dust related diseases.

Helicobacter pylori potentiates histamine release from serosal rat mast cells in vitro

Helicobacter pylori seems to be involved in the etiology of peptic ulcer and chronic gastritis. Histamine is fundamental in gastric secretion modulation, and some features of H. pylori-associated gastritis (edema, vasodilatation, inflammatory cell infiltration) are typical of the histamine-mediated response. This in vitro study has been undertaken as a preliminary step, in order to find a possible link between H. pylori and histamine release. H. pylori isolated from gastric biopsies has been tested as whole washed bacterium, whole formalin-killed bacterium, and crude cell wall preparation with serosal mast cells obtained by density gradient centrifugation or elutriation from peritoneal and pleural washings of male Wistar albino rats. Histamine release was assayed fluorimetrically. No significant histamine release was obtained by testing the various bacterial preparations alone with mast cells. On the contrary, whole washed cells, whole formalin-killed cells and crude cell walls from H. pylori have been found to potentiate compound 48/80 or calcium ionophore A23187-induced histamine release. Crude cell walls showed the highest activity, whereas filtered supernatants from broth cultures constantly appeared inactive. The enhancement in histamine release differed between the different strains. The present in vitro study, which shows the potentiating effect of H. pylori on histamine release, may prove interesting; however, at present, clinical implications cannot be inferred and further studies as well as in vivo demonstrations are needed.

Axonal necrosis of enteric autonomic nerves in continent ileal pouches. Possible implications for pathogenesis of Crohn's disease

OBJECTIVE

Axonal necrosis was first described in samples of small intestine from patients with Crohn's disease (A.M. Dvorak et al. Hum Pathol 1980; 11:620-634). Clinically evident inflammation of continent ileal reservoirs (pouches) has clinical features that resemble Crohn's disease. Possible similarities in the pathogenesis of Crohn's disease and pouchitis were sought using ultrastructural and microbiologic tools to identify damaged enteric nerves and tissue bacteria.

METHODS

An encoded ultrastructural and microbiologic study of replicate biopsies from 114 samples of human intestine was done. Biopsies from ileum, colon, conventional ileostomy or continent pouch were obtained from patients with ulcerative colitis, Crohn's disease, or familial polyposis and grouped into three clinical study groups (control, normal pouch, pouchitis), based on clinical and endoscopic criteria. Biopsies were prepared for electron microscopy with standard methods; replicate biopsy samples were washed extensively before preparing cultures designed to identify aerobic as well as facultative and obligate anaerobic bacteria (Onderdonk et al. J Clin Microbiol 1992; 30:312-317). The ultrastructural diagnosis of damaged enteric nerves was based on previously published criteria for axonal necrosis (A.M. Dvorak and W. Silen. Ann Surg 1985; 201:53-63). Intergroup comparisons were tested for significance using Chi-square analysis.

RESULTS

The highest incidence of axonal necrosis was present in Crohn's disease control biopsies (53%), regardless of whether bacteria were present (or not) in cultures of replicate biopsies. Axonal necrosis also occurred in more ulcerative colitis and familial polyposis biopsies (regardless of biopsy site) that had positive bacterial cultures than in those that did not (p < 0.001). In addition, axonal necrosis was documented in 42% of the pouch biopsies from ulcerative colitis and familial polyposis patients, particularly in those pouches that were found to be inflamed by clinical criteria and that also had positive bacterial cultures of the biopsied tissues. Control biopsies from patients with ulcerative colitis and familial polyposis had significantly less nerve damage than pouch biopsies in the presence of positive cultures (p < 0.01). Among the clinically inflamed pouches biopsied in ulcerative colitis or familial polyposis patients, we found that none had damaged enteric nerves when bacterial cultures were negative (p < 0.005). If the presence of axonal necrosis alone was compared with the presence of undamaged enteric nerves in all biopsies from patients with ulcerative colitis, a highly significant number of ulcerative colitis biopsies with axonal necrosis occurred in pouches (72%) compared with controls (p < 0.001).

CONCLUSIONS

The ultrastructural finding of axonal necrosis in Crohn's disease confirms previous studies. The presence of damaged enteric nerves in patients with pouchitis provides ultrastructural support to the clinical impression of similarities between pouchitis and Crohn's disease. The association of damaged nerves and invasive bacteria in pouchitis suggests mechanistic similarities for the pathogenesis of Crohn's disease that requires further investigation.

Staphylococcus aureus modifies the cytokine-induced immunoglobulin synthesis and CD23 expression in patients with atopic dermatitis

The influence of Staphylococcus aureus on peripheral blood lymphocytes (PBL) of patients with atopic dermatitis (AD) was analysed. The parameters studied were spontaneous and interleukin-inducible immunoglobulin (IgA, IgE, IgG) synthesis, as well as CD23 expression. Various heat-killed, clinical isolates of S. aureus were analysed. PBL from non-atopic donors served as controls. The time-course of co-cultured PBL with S. aureus showed a dose-dependent increase in immunoglobulin (Ig) synthesis from PBL of normal donors, whereas the Ig synthesis of atopic cells was significantly depressed. Additional stimulation with interleukin-4 (IL-4) also led to a pronounced suppression of the IgE and IgA synthesis in normal donor cells, while the effect of S. aureus on PBL of atopic donors was not markedly affected by IL-4. Transwell cultures of bacteria separated from PBL by a semi-permeable membrane induced stimulation of IgA and IgE synthesis in patients with AD. The Ig synthesis in the control group was not altered. Co-stimulation of S. aureus and IL-4 in this system led to a suppression of IgA with cells of both atopic and normal donors. IgE synthesis from atopic PBL was significantly stimulated. The CD23 expression of atopic PBL was increased by S. aureus and IL-4. Our data indicate that S. aureus may modulate the cytokine-dependent humoral immunity in patients with AD and that chronic colonization of the skin may be responsible for allergic skin reactions in AD.

Virus, bacteria and lipopolysaccharide increase basophil cell response to histamine releasing stimulators and calcium. Examination of allergic and normal individuals

Histamine release from human basophil leukocytes from allergic patients or controls was induced by specific antigens, anti-IgE or calcium ionophore A23187. Influenza A virus, S. aureus and lipopolysaccharide from S. typhimurium increased the maximum release of histamine and caused a shift to the left of the dose-response curves showing increased cell sensitivity and lowering of the threshold to these stimuli. The mechanism of action was elucidated by examining the mediator release as a function of increasing extracellular concentration of calcium. In these experiments the dose-response curves were changed by the microorganisms and lipopolysaccharide as before. This indicates that the microorganisms and lipopolysaccharide change the basophil cell response to IgE-dependent and non-immunological stimuli by causing a change in the subcellular handling of calcium.

Bacteria-induced histamine release from human bronchoalveolar cells and blood leukocytes

Histamine release induced by Staphylococcus aureus was examined in cells obtained by bronchoalveolar lavage (BAL) in non-atopic individuals. Approximately half of the individuals responded with mediator release to the bacterium, and the release was found to be time- and concentration dependent. No difference was found between the patients who responded and those who did not respond in regard to age, sex, smoker/non-smoker, % recovery of BAL-fluid, total cell count, differential cell counts, histamine content per mast cell, or diagnoses. Also stimulation of the BAL-cells with the calcium-ionophore A23187 resulted in histamine release. S. aureus-induced histamine release from basophils was examined in leukocyte suspensions obtained from the same individuals, and in all experiments release was found. The dose-response curves were similar to those obtained with BAL cells. The bacteria-induced mediator release from superficially lying cells in the airways epithelium might be of importance for the precipitation or exacerbation of bronchial asthma in respiratory tract infections.

Influenza A virus potentiates bacteria-induced histamine release. Examination of normal individuals and patients allergic to bacteria

Influenza A virus was found to enhance basophil histamine release induced by Escherichia coli, Salmonella enteritidis, Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus sanguis, but did not per se release histamine. This potentiating effect of the virus was seen both when the bacteria-induced mediator release was IgE-dependent (i.e. patient allergic to bacterium) and when the bacterium caused histamine release by a non-immunological mechanism independent of IgE (putative sugar-lectin mediated). Also histamine release induced by other immunological and non-immunological stimuli, such as anti-IgE, calcium ionophore or agarose beads was enhanced in the presence of the virus. The potentiating effect of the virus on bacteria-induced mediator release might be of importance for the conversion from latent to manifest asthma in upper respiratory tract infections.

Bacteria and endotoxin enhance basophil histamine release and potentiation is abolished by carbohydrates

Histamine release caused by anti-IgE, specific antigens and calcium ionophore A23187 was examined in leukocyte suspensions from healthy individuals and patients allergic to house dust mite and birch pollen. Staphylococcus aureus and LPS from Salmonella typhimurium were found to cause a synergistic enhancement of the release. The potentiation of mediator release by the bacteria and the endotoxin depends on a binding to the basophilocyte, followed by a non-transient event, since the potentiating effect persists after preincubation of the cells with the LPS followed by washout and leaving the cells for 30 min at 37 degrees C before stimulation with anti-IgE. The potentiation was abolished or reduced by galactose (10(-7) and 10(-6) M) and N-acetylglucosamine (10(-6) and 10(-5) M), acting by a binding to the basophil cell membrane, demonstrated by the persistence of effect after preincubation and washout of unbound sugar.

Vancomycin-induced histamine release and "red man syndrome": comparison of 1- and 2-hour infusions

Vancomycin-induced "red man syndrome" (RMS) is mediated in part by histamine release, and its severity is correlated with the area under the plasma histamine concentration-time curve. Ten adult male volunteers participated in a randomized, double-blind, two-way crossover trial (1-week washout interval between regimens) to determine the effect of 1- and 2-h infusions of vancomycin (1.0 g) on histamine release and on the frequency and severity of RMS. The severity of RMS was classified a priori as mild, moderate, or severe from a combined score of pruritus and extent of erythema. Serial concentrations of histamine in plasma and concentrations of vancomycin in serum were measured at baseline and during and after each infusion. Of 10 subjects, 8 had evidence of RMS during the 1-h infusion (3 mild, 3 moderate, and 2 severe), whereas only 3 of the 10 subjects (all mild) had RMS during the 2-h infusion (P less than 0.05). The 1-h infusion was associated with a significantly greater peak concentration of histamine in plasma (1.8 +/- 0.7 versus 1.0 +/- 0.3 ng/ml, P = 0.004) and a greater total release of histamine (74.3 +/- 54.1 versus 36.4 +/- 22.6 ng.min/ml, P = 0.017) than was the 2-h infusion. These data suggest that administration of vancomycin over 2 h reduces the frequency and severity of RMS and the amount of histamine released compared with those after a 1-h infusion in healthy volunteers.

Virus enhances IgE- and non-IgE-dependent histamine release induced by bacteria and other stimulators

Histamine release from human basophil leukocytes was triggered by Staph. aureus, Salmonella enteritidis, non-haemolytic streptococci, or E. coli. Influenza A virus was found to enhance the mediator release and the effect was caused by synergism, since the virus did not induce release of histamine per se. This potentiating effect of the virus was seen both when the bacteria-induced histamine release was IgE-dependent (i.e. patient sensitized to the bacterium) and when the bacterium caused mediator release by a non-immunological mechanism independent of IgE (putative sugar-lectin mediated). Histamine release induced by anti-IgE and calcium ionophore or agarose-beads was also enhanced in the presence of the virus. These findings indicate that influenza A virus potentiates both IgE- and non-IgE-mediated histamine release induced by bacteria and other stimulators.

Endotoxin from Haemophilus influenzae enhances IgE-mediated and non-immunological histamine release

Haemophilus influenza and its extracellular products (EP) did not release histamine from basophil leukocytes in cell suspensions from normal individuals, patients with chronic bronchitis or patients allergic to either house dust mite, grass pollen, cat dander or to their own bacteria. However, the EP was found to enhance their basophil histamine release. IgE-mediated histamine release was examined by stimulation of the cells with anti-IgE or the specific allergens, and non-immunological histamine release by stimulating the cells with the calcium ionophore A23187 or Staphylococcus aureus. In all the experiments EP caused a significant increase in the histamine release. When H. influenzae endotoxins were removed from the EP, the potentiating effect of EP was completely abolished, whereas heating (80 degrees C, 30 min) or treatment of EP with proteinase did not influence the potentiating effect. These results indicate that H. influenzae endotoxin potentiates histamine release caused by IgE-mediated reactions or by non-immunological mechanisms.

Staphylococcus aureus and influenza A virus stimulate human bronchoalveolar cells to release histamine and leukotrienes

Mediator release was examined from superficially lying cells in the airway epithelium obtained by bronchoalveolar lavage (BAL) in 13 non-atopic individuals. The BAL-cells were incubated (20 min, 37 degrees C) with Staphylococcus (Staph.) aureus or with human influenza A virus Staph. aureus was found to release histamine from cells from 7 of the 13 individuals and influenza A virus in 3 of 5 persons. Furthermore, Staph, aureus stimulated the BAL-cells to release leukotriene B4 in 7 of 11 subjects, whereas no release was found by influenza A virus in 7 examined persons. When cells from 4 persons were stimulated with Staph. aureus no release of leukotriene C4 was found. The mediator release caused by bacteria and virus might be of importance for the exacerbation of bronchial asthma in upper respiratory tract infections, since histamine is assumed to increase the epithelial permeability with entrance of allergens and other insulting particles, and leukotriene B4 facilitates airway inflammation.

Influenza A virus enhances Staphylococcus aureus-induced basophil histamine release in normal individuals and patients with intrinsic asthma

Influenza A virus was found to enhance Staphylococcus aureus-induced histamine release in human leukocyte suspensions, but did not per se release histamine. This potentiating effect was found to be similar in cells from normal individuals and from patients with intrinsic asthma. The enhancement of mediator release could be due to viral neuraminidase on the surface of the virus, since a similar potentiating effect was caused by a purified neuraminidase preparation obtained from Vibrio cholerae, and the effect of virus as well as of the purified neuraminidase was completely abolished by a potent neuraminidase inhibitor. The potentiating effect of virus on bacteria-induced mediator release might be of importance for the conversion from latent to manifest asthma in upper respiratory tract infections.

Virus enhances histamine release from human basophils

Histamine release from human basophil leukocytes was triggered by Staph. aureus or by complement activation caused by endotoxins isolated from E. coli or Salmonella bacteria. Influenza A virus was found to enhance the mediator release and the effect was caused by synergism, since the virus itself did not release histamine. The potentiating effect of the virus was abolished by a potent neuraminidase inhibitor. Furthermore, a purified neuraminidase preparation obtained from Vibrio cholerae caused a similar potentiating effect, which was also abolished by the neuraminidase inhibitor. These findings indicate that the neuraminidase on the surface of influenza A virus is responsible for the potentiating effect of the virus on basophil histamine release.

Histamine release from human adenoidal and mesenteric mast cells induced by bacterial antigens

The histamine-releasing capability of Staphylococcus aureus antigens was examined in human adenoidal and mesenteric mast cells obtained by enzymic dispersion of tissues from non-allergic patients. Both populations of mast cells released histamine after challenge with bacterial protein in concentrations between 5-500 micrograms/ml. The release was dependent on the dose, temperature and metabolic energy. The maximum release was observed at 15 min after challenge. The present results suggest that Staphylococcus aureus antigens release histamine from human adenoidal and mesenteric mast cells via a non-cytotoxic, active secretory process.

Non-IgE-dependent bacteria-induced histamine release from human lung and tonsillar mast cells

A wide spectrum of formalin-killed bacteria have been tested for their ability to release histamine from human dispersed lung and tonsillar mast cells. Escherichia coli, Enterobacter cloacae, Staphylococcus epidermidis, Proteus vulgaris, Klebsiella oxytoca and K. pneumoniae were the most effective histamine releasers. Further studies on tonsillar mast cells showed that E. coli-induced histamine release differed from IgE-dependent release with respect to its kinetics, temperature and pH profiles and its sensitivity to calcium deprivation and metabolic inhibitors. A lectin-mediated mechanism may operate, but other non-immunological mechanisms might also be involved in the release. Escherichia coli and anti-IgE did not synergize in inducing histamine release. The production of PGD2 and the failure to detect lactate dehydrogenase following incubation of mast cells with E. coli suggests that histamine release is not due to cytotoxicity.

Bacteria and their products peptidoglycan and teichoic acid potentiate antigen-induced histamine release in allergic patients

Histamine release was examined in leukocyte suspensions from patients allergic to grass pollen, mite or cat dander or to bacteria (antigen). When the cells were challenged with specific antigen plus bacteria to which the person was not sensitized, these bacteria were found to potentiate the allergic histamine release. The potentiating effect by bacteria might be due to the bacterial cell wall components, peptidoglycan and teichoic acid, which mimic the effect of bacteria.

Histamine release induced by bacteria. A new mechanism in asthma?

Bacteria release histamine from human basophil leukocytes and mast cells. The release can be caused by an immunological (IgE-dependent) mechanism, but mostly we found a non-immunological (lectin-mediated) mechanism which indicates that mediator release triggered by bacteria can occur without the person being sensitized to the micro-organism in question. Both bacteria and bacterial products such as endotoxins potentiate basophil histamine release caused by allergens in allergic patients or by bacteria in persons sensitized to the micro-organisms. It is therefore tempting to speculate that bacteria and their products might be of importance for asthma by their capacity to release histamine and to potentiate mediator release.

Endotoxins release histamine by complement activation and potentiate bacteria-induced histamine release

The histamine-releasing capability of bacterial lipopolysaccharides (LPS) was examined in human leukocyte suspensions. LPS alone did not release histamine, but it was found to enhance the histamine release caused by bacteria in basophils from persons sensitized to these bacteria. In the presence of serum, LPS was able to release histamine through complement activation. It is speculated that endotoxins reinforce release of histamine caused by bacteria in persons sensitized to these microorganisms, and a direct mediator release via complement activation might play a role in septic conditions.

Influence of bacterial endotoxins on basophil histamine release. Potentiation of antigen- and bacteria-induced histamine release

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.