Inhibition of histamine release in vitro by a blocking factor from human serum: comparison with the iron binding proteins transferrin and lactoferrin

Ameliorating Atopy by Compensating Micronutritional Deficiencies in Immune Cells: A Double-Blind Placebo-Controlled Pilot Study

BACKGROUND

Functional iron deficiency facilitates allergy development and amplifies the symptom burden in people experiencing allergies. Previously we selectively delivered micronutrients to immune cells with β-lactoglobulin as carrier (holoBLG), resulting in immune resilience and allergy prevention.

OBJECTIVE

The clinical efficacy of a food for special medical purposes-lozenge containing β-lactoglobulin with iron, polyphenols, retinoic acid, and zinc (holoBLG lozenge) was assessed in allergic women.

METHODS

In a randomized, double-blind, placebo-controlled pilot study, grass- and/or birch pollen-allergic women (n = 51) were given holoBLG or placebo lozenges over 6 months. Before and after dietary supplementation, participants were nasally challenged and the blood was analyzed for immune and iron parameters. Daily symptoms, medications, pollen concentrations, and well-being were recorded by an electronic health application.

RESULTS

Total nasal symptom score after nasal provocations improved by 42% in the holoBLG group versus 13% in the placebo group. The combined symptom medication score during the birch peak and entire season as well as the entire grass pollen season improved in allergic subjects supplemented with the holoBLG lozenge by 45%, 31%, and 40%, respectively, compared with the placebo arm. Participants ingesting the holoBLG lozenge had improved iron status with increased hematocrit values, decreased red cell distribution width, and higher iron levels in circulating CD14⁺ cells compared with the placebo group.

CONCLUSIONS

Targeted micronutrition with the holoBLG lozenge seemed to be effective in elevating the labile iron levels in immune cells and reducing the symptom burden in allergic women in this pilot study. The underlying allergen-independent mechanism provides evidence that dietary nutritional supplementation of the immune system is one of the ways to combat atopy.

Cow's milk protein β-lactoglobulin confers resilience against allergy by targeting complexed iron into immune cells

BACKGROUND

Beta-lactoglobulin (BLG) is a bovine lipocalin in milk with an innate defense function. The circumstances under which BLG is associated with tolerance of or allergy to milk are not understood.

OBJECTIVE

Our aims were to assess the capacity of ligand-free apoBLG versus loaded BLG (holoBLG) to protect mice against allergy by using an iron-quercetin complex as an exemplary ligand and to study the molecular mechanisms of this protection.

METHODS

Binding of iron-quercetin to BLG was modeled and confirmed by spectroscopy and docking calculations. Serum IgE binding to apoBLG and holoBLG in children allergic to milk and children tolerant of milk was assessed. Mice were intranasally treated with apoBLG versus holoBLG and analyzed immunologically after systemic challenge. Aryl hydrocarbon receptor (AhR) activation was evaluated with reporter cells and Cyp1A1 expression. Treated human PBMCs and human mast cells were assessed by fluorescence-activated cell sorting and degranulation, respectively.

RESULTS

Modeling predicted masking of major IgE and T-cell epitopes of BLG by ligand binding. In line with this modeling, IgE binding in children allergic to milk was reduced toward holoBLG, which also impaired degranulation of mast cells. In mice, only treatments with holoBLG prevented allergic sensitization and anaphylaxis, while sustaining regulatory T cells. BLG facilitated quercetin-dependent AhR activation and, downstream of AhR, lung Cyp1A1 expression. HoloBLG shuttled iron into monocytic cells and impaired their antigen presentation.

CONCLUSION

The cargo of holoBLG is decisive in preventing allergy in vivo. BLG without cargo acted as an allergen in vivo and further primed human mast cells for degranulation in an antigen-independent fashion. Our data provide a mechanistic explanation why the same proteins can act either as tolerogens or as allergens.

Iron-binding properties of bovine lactoferrin in iron-rich solution

The iron-binding properties of bovine lactoferrin in iron-rich solution were investigated. Ferrous iron was not stable in solution and was easily changed to the insoluble ferric state, but solubility of ferrous iron was stabilized by the presence of lactoferrin. However, casein hydrolysate or BSA was not effective in stabilizing iron in solution. As indicated by use of cibacron blue affinity gel, iron bound to lactoferrin, and the charge of supersaturated lactoferrin was higher than that of normal iron-saturated lactoferrin according to native PAGE electrophoresis. The evidence suggests that lactoferrin can bind iron at sites other than its chelate-binding sites, thereby stabilizing iron in solution.

Activation of human complement by rat peritoneal mast cells and its inhibition by a rat serum factor

The effects of normal sera from humans, rats, and guinea pigs on unsensitized rat peritoneal mast cells were studied in vitro. Five to 20% fresh human sera induced mast cell death and substantial histamine release. The factor was heat labile. Neither hereditary C3-deficient sera nor experimentally C1q-depleted sera showed cytotoxicity. The CH50 activity of human serum was decreased to about one half after a 15-min incubation with 2 X 10(6) mast cells/ml at 37 degrees C. The cytotoxic activity and CH50 reduction were completely eliminated by an addition of 10 mM Mg-EGTA to the serum. These data demonstrated that unsensitized rat mast cells served as both the initiator and target of complement activity when human serum was used as a complement source. Requirements of both Ca++ and C1q suggested the activation of the classical pathway of complement. Fresh 5-20% sera from rats and guinea pigs, on the other hand, showed neither cytotoxicity nor CH50 reduction. Furthermore, these sera strongly inhibited the human serum-induced reaction. The latter results indicated the presence of a modulating factor in rat and guinea pig sera, which inhibits mast cell associated complement activation.

Inhibition of histamine release from rat peritoneal mast cells by a factor from human serum--identification as transferrin

Recently, we described the presence of a blocking factor (BF) in rat serum which inhibited the histamine release from rat mast cells in vivo and in vitro. The blocking activity was demonstrated in human serum as well. Purification of the human-BF was carried out in a similar way as previously described for the rodent molecule. Both protein fractions produced a marked suppression of histamine release from rat mast cells and human basophils in a dose-dependent fashion. Qualitative analysis of the purified preparations demonstrated a major component with a molecular weight of 70,000 daltons. In human serum the blocking factor was identified as transferrin by serological and biochemical methods. It is suggested that this molecule may play an important role in regulating histamine release during allergic and inflammatory reactions.