Secretory IgA-mediated basophil activation. II. Roles of GTP-binding regulatory proteins and phosphatidylinositol 3-kinase

Antibody-mediated regulation of basophils: emerging views and clinical implications

An increasing number of human diseases, including allergies, infections, inflammation, and cancer, involve roles for basophils. Traditionally viewed as the rarest leukocytes that are present only in the circulation, basophils have recently emerged as important players in systemic as well as tissue-specific immune responses. Their functions are regulated by immunoglobulins (Igs), and this enables basophils to integrate diverse adaptive and innate immunity signals. IgE is well known to regulate basophil responses in the context of type 2 immunity and allergic inflammation; however, growing evidence shows that IgG, IgA, and IgD also shape specific aspects of basophil functions relevant to many human diseases. We discuss recent mechanistic advances underpinning antibody-mediated basophil responses and propose strategies for the treatment of basophil-associated disorders.

Identification of ANXA2 on epithelial cells as a new receptor for secretory IgA using immunoprecipitation and mass spectrometry

Secretory immunoglobulin A plays an important role in the protection against exogenous pathogens and antigens, but it has also been reported to have pathogenic potential. We previously found that secretory immunoglobulin A accumulated in the peripheral lungs during idiopathic pulmonary fibrosis and that transferrin receptor/CD71 was partially involved in secretory immunoglobulin A-induced inflammatory cytokine production in A549 cells. This study aimed to identify the receptor responsible for the induction of cytokine production by secretory immunoglobulin A-stimulated airway epithelial cells. To this end, immunoprecipitation followed by time-of-flight mass spectrometry and peptide mass fingerprinting were performed and Annexin A2 was detected as a novel receptor for secretory immunoglobulin A. Enzyme-linked immunosorbent assay demonstrated binding of secretory immunoglobulin A to Annexin A2, and flow cytometry showed robust expression of Annexin A2 on the surface of BEAS-2B cells, A549 cells, and normal human bronchial/tracheal epithelial cells. Experiments in A549 cells using Annexin A2 small interfering RNA and neutralizing antibodies suggested that Annexin A2 was partially involved in the production of interleukin-8/CXCL8 and C-C motif chemokine ligand 2/monocyte chemoattractant protein-1 induced by secretory immunoglobulin A. Immunohistochemistry using lung sections revealed clear expression of Annexin A2 on airway epithelial cells, although the staining remained equivalent in idiopathic pulmonary fibrosis, asthma, and healthy control lungs. In conclusion, we identified that Annexin A2 expressed in airway epithelial cells is a novel receptor for secretory immunoglobulin A, which is involved in cytokine synthesis.

Effect of nasal antihistamine on secretory IgA in nasal lavage of rats

The humoral IgA is an immunoglobulin which plays a defensive role for organisms on mucosal surfaces. Today, intranasal antihistamines are effectively used in the treatment of allergic rhinitis. In our study, the effect of azelastine hydrochloride-a nasal antihistaminic-on humoral IgA of the nasal mucosa has been reviewed empirically. Twenty-four female Sprague-Dawley rats were included in our study. The rats were divided into three groups randomly. Group 1(azelastine hydrochloride): rats in this group had nasal azelastine hydrochloride (0.05%) applied for 30 days at 10 µl/nostril dosage. Group 2 (saline): saline (0.09%) was applied to the rats in this group for 30 days at 10 µl/nostril dosage. Group 3 (control): no application was made throughout the study. The chemicals applied in Groups 1 and 2 were applied to both nostrils by mounting a flexible micropipette to the end of an insulin injector. At the beginning of the study, nasal lavage was performed to both nostrils of the rats in every group on the 15th and 30th day to aspirate irrigation solution (distilled water). The aspirated liquids were kept at - 80° temperature and reviewed together at the end of study. Within-group comparisons: in Group 1 (azelastine hydrochloride), the humoral IgA value on the 15th day was significantly higher than the basal value (p = 0.037). There is a significant difference between humoral IgA value on the 30th day and humoral IgA value on the 15th day (p = 0.045). In Group 2 (saline), no significant difference is available between basal, 15th day and 30th day humoral IgA values (p = 0.265). In Group 3 (control), no significant difference is available between basal, 15th day and 30th day humoral IgA values (p = 0.374). Between-group comparison: there is no significant difference in between-group humoral IgA basal values (p = 0.714). On days 15 and 30, Humoral IgA value of Group 1 was significantly higher than that of Groups 2 and 3 (p = 0.013, p = 0.024, respectively). According to the results we achieved in our study, nasal antihistaminic (azelastine hydrochloride) significantly increases the level of humoral IgA. Our study is the first one in the literature to reveal a relation between nasal antihistaminic and humoral IgA and there is a further need for clinical, randomized and prospective studies.

The Evolution of Human Basophil Biology from Neglect towards Understanding of Their Immune Functions

Being discovered long ago basophils have been neglected for more than a century. During the past decade evidence emerged that basophils share features of innate and adaptive immunity. Nowadays, basophils are best known for their striking effector role in the allergic reaction. They hence have been used for establishing new diagnostic tests and therapeutic approaches and for characterizing natural and recombinant allergens as well as hypoallergens, which display lower or diminished IgE-binding activity. However, it was a long way from discovery in 1879 until identification of their function in hypersensitivity reactions, including adverse drug reactions. Starting with a historical background, this review highlights the modern view on basophil biology.

Basophil activation test in oral desensitization to cow's milk allergy

The recent paper by Nucera et al., showed that the basophil activation test (BAT) in flow cytometry is able to monitor an acquired tolerance induced by a desensitization treatment in food allergy. The paper by Nucera et al. reported two standpoints in the CD63 response to food allergy and OAT and their large difference in CD63 response before and after suggests for the optimal performance of a CD123/HLADR/CD63 BAT in oral food allergy immunotherapy.

Immunotherapy in allergy and cellular tests: state of art

The basophil activation test (BAT) is an in vitro assay where the activation of basophils upon exposure to various IgE-challenging molecules is measured by flow cytometry. It is a cellular test able to investigate basophil behavior during allergy and allergy immunotherapy. A panoply of critical issues and suggestive advances have rendered this assay a promising yet puzzling tool to endeavor a full comprehension of innate immunity of allergy desensitization and manage allergen or monoclonal anti-IgE therapy. In this review a brief state of art of BAT in immunotherapy is described focusing onto the analytical issue pertaining BAT performance in allergy specific therapy.

IgA receptors in health and disease

The varied interaction of the Fc region of IgA with receptors confers this antibody class with many of its unique properties. The epithelial polymeric Ig receptor on mucosal epithelial cells transports polymeric immunoglobulin A (pIgA) produced by mucosal B cells to the mucosal surface where, in complex with the secretory component (SC), this secretory immunoglobulin A (SIgA) excludes the multitude of dietary, environmental, and microbial antigens that continuously bombard the mucosae. In health, this IgA-mediated exclusion not only forms the initial defence against infection, it also spares the systemic immune system from potentially deleterious responses to innocuous antigens which can otherwise culminate in inflammatory bowel disease or asthma. Beyond antigen exclusion, in closer encounters with antigens, IgA receptors play roles in protective immunity and disease. FcaRI is the principal myeloid IgA receptor and is responsible for differing IgA-mediated effector responses such as respiratory burst, degranulation, and phagocytosis variously by granulyoctes, monocytes, and macrophages. Furthermore an unknown IgA receptor specific for the secretory component (SC) elicits powerful effector responses from eosinophils. On dendritic cells, FcaRI participates in antigen presentation while on microfold cells, key cells in mucosal antigen presentation, another unknown IgA receptor functions in the transport of antigens across the mucosal epithelial barrier. The activity of another uncharacterized IgA1/IgD receptor on T cells may affect autoimmune disorders. The interplay of different IgA receptors affects immune complex deposition in the common renal disease immunoglobulin A nephropathy (IgAN). Finally, the therapeutic application of various IgA receptors has been sought in the areas of infectious disease, vaccines, and cancer.

Secretory IgA, free secretory component and IgD in saliva of newborn infants

AIM

To determine levels of secretory IgA (sIgA), free secretory component (FSC) and IgD in saliva of newborn infants at the age of 1 day and to evaluate the detection patterns, the influence of saliva flow and the relation to serum derived proteins.

METHODS

Seventy-three healthy newborn infants were studied. Saliva was obtained from the bottom of the mouth and buccal sulci using a sterile polyethylene tube connected to a syringe. SIgA, FSC, IgD and albumin were measured by radial immunodiffusion.

RESULTS

SIgA was detected in 74.0% of all saliva samples, whereas detection rates for FSC and IgD were 94.5% and 75.3%, respectively. Investigation of detection patterns and their relation to saliva flow indicated that secretion of sIgA and FSC into the oral cavity is under similar regulation. Levels of IgD were found to be independent from saliva flow, as well as from concentrations of serum-derived proteins suggesting different regulative mechanisms compared to sIgA and FSC. The flow rate of unstimulated whole saliva in newborn infants was found to be 15 times lower compared to adolescents, emphasizing the role of saliva flow as a limiting factor for secretion of sIgA and FSC.

CONCLUSION

SIgA, FSC and IgD can be determined in saliva of newborn infants even in the first day of life. The saliva flow rate has to be considered when evaluating the function and biological relevance of the oral mucosal immune system of newborn infants shortly after birth.