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B cell superantigens, also called immunoglobulin superantigens, bind to the variable regions of either the heavy or light chain of immunoglobulins mirroring the lymphocyte-activating properties of classical T cell superantigens. Protein A of Staphylococcus aureus, protein L of Peptostreptococcus magnus, and gp120 of HIV are typical immunoglobulin superantigens. Mast cells are immune cells expressing the high-affinity receptor for IgE (FcεRI) and are strategically located in the human heart, where they play a role in several cardiometabolic diseases. Here, we investigated whether immunoglobulin superantigens induced the activation of human heart mast cells (HHMCs). Protein A induced the de novo synthesis of cysteinyl leukotriene C4 (LTC4) from HHMCs through the interaction with IgE VH3+ bound to FcεRI. Protein L stimulated the production of prostaglandin D2 (PGD2) from HHMCs through the interaction with κ light chains of IgE. HIV glycoprotein gp120 induced the release of preformed (histamine) and de novo synthesized mediators, such as cysteinyl leukotriene C4 (LTC4), angiogenic (VEGF-A), and lymphangiogenic (VEGF-C) factors by interacting with the VH3 region of IgE. Collectively, our data indicate that bacterial and viral immunoglobulin superantigens can interact with different regions of IgE bound to FcεRI to induce the release of proinflammatory, angiogenic, and lymphangiogenic factors from human cardiac mast cells.

Background: Common variable immunodeficiency (CVID) encompasses a heterogeneous group of primary antibody deficiency disorders characterized by recurrent infections, autoimmunity and malignancies. Gastrointestinal manifestations are frequently associated with CVID. Objective: In this cross-sectional study, we evaluated gastric and duodenal involvement in a cohort of adult patients with CVID. Methods: Upper gastrointestinal endoscopy was performed in 58 patients (26 males, mean age 47.8±15.6 years), diagnosed with CVID according to 2014 ESID criteria. Random biopsies were collected from gastric antrum and descending duodenum for the all enrolled subjects. Intraepithelial lymphocytosis in descending duodenum was defined as the presence of 25 lymphocytes per 100 enterocytes. Results: The major histopathological findings that we found were: a) chronic active gastritis (44.8%), Helicobacter pylori-associated (8.6%), b) chronic duodenitis (39.6%) with intraepithelial lymphocytosis (31%) and absence of plasma cells (18.9%) and c) autoimmune atrophic gastritis (5.2%). Three patients (5.2%) presented Intestinal Metaplasia (IM) of the gastric antrum. This finding was associated with H. pylori infection and persisted after the eradication in one patient. IM was associated with autoimmune atrophic gastritis in two cases. Giardia lamblia infection was observed in the duodenum samples from three patients (5.2%). A diagnosis of Gastric adenocarcinoma was made in a 58-year-old woman diagnosed with gastric dysplasia one year earlier. Conclusion: In our cohort of CVID patients, gastro-duodenal histopathological findings, including malignancies, are frequent and can affect long-term prognosis. A rigorous endoscopic follow-up is needed in CVID patients irrespective of the gastrointestinal symptoms.

Secreted phospholipases A(2) (sPLA(2)s) are molecules released in plasma and biological fluids of patients with systemic inflammatory, autoimmune and allergic diseases. These molecules exert proinflammatory effects by either enzymatic-mechanisms or through binding to surface molecules expressed on inflammatory cells. sPLA(2)s are released at low levels in the normal airways and tend to increase during respiratory allergies (e.g., rhinitis and bronchial asthma) as the result of local secretion. Several sPLA(2) isoforms are expressed in the human lung and some of them (e.g., group IIA and group X) are released in the airways of patients with rhinitis or asthma. Mast cells play a major role in the pathogenesis of respiratory allergies and other chronic inflammatory lung diseases. Recent evidence indicates that mast cells purified from human lung express most of the sPLA(2) isoforms so far described. IgE-mediated activation of these cells induce the release of sPLA(2)s suggesting that mast cells are a main source of extracellular sPLA(2)s during allergic reactions. Once released, sPLA(2)s may contribute to the generation of eicosanoids (e.g., PGD(2) and LTC(4)) and to the release of preformed mediators (e.g., histamine) by an autocrine loop involving the interaction of sPLA(2)s with surface molecules such as heparan sulphate proteoglycans or the M-type receptor. Thus, mast cell-derived sPLA(2)s may play an important role in the initiation and amplification of the inflammatory reactions in patients with allergic rhinitis and bronchial asthma.

Angiogenesis and lymphangiogenesis are distinct and complex processes requiring a finely tuned balance between stimulatory and inhibitory signals. Immune and inflammatory cells can contribute to these processes by multiple mechanisms: directly by producing a broad array of angiogenic growth factors, and indirectly by secreting several cytokines, chemokines and other mediators able to coordinate the cell-cell interactions. Immune cells can stimulate or inhibit angiogenesis/lymphangiogenesis, depending on their activation status and subset specificity. We summarize recent findings reporting the expression and activity of angiogenic and lymphangiogenic factors and their receptors and coreceptors in immune cells. It is evident that modulation of angiogenesis and lymphangiogenesis by the innate and adaptive immune cells (mast cells, macrophages, dendritic cells, basophils, eosinophils, and some subsets of T cells) is a highly complex process not yet completely understood.