Eosinophil in the context of "Neutrophil"

The high-affinity IgE receptor, also known as FcεRI, or Fc epsilon RI, is the high-affinity receptor for the Fc region of immunoglobulin E (IgE), an antibody isotype involved in allergy disorders and parasite immunity. FcεRI is a tetrameric receptor complex that binds Fc portion of the ε heavy chain of IgE. It consists of one alpha (FcεRIα – antibody binding site), one beta (FcεRIβ – which amplifies the downstream signal), and two gamma chains (FcεRIγ – the site where the downstream signal initiates) connected by two disulfide bridges on mast cells and basophils. It lacks the beta subunit on other cells. It is constitutively expressed on mast cells and basophils and is inducible in eosinophils.

A granulocyte transfusion is a medical procedure in which granulocytes are infused into a person's blood. Granulocytes are a category of white blood cell that includes neutrophils, eosinophils, and basophils. Granulocyte transfusions were historically used to prevent and treat infections in people with neutropenia (an abnormally low level of neutrophils), but the practice declined in popularity in the 1980s. Interest in the procedure increased in the 1990s due to the development of more effective methods for harvesting granulocytes and a growing population of people with severe neutropenia from chemotherapy. However, the treatment's efficacy remains poorly understood and its use is controversial.

Granulocytes are most often collected through leukapheresis, a process that separates the donor's white blood cells from their red blood cells and plasma. Donors may be given corticosteroids or granulocyte colony-stimulating factor to increase their granulocyte count prior to the blood collection. Granulocytes have a short shelf life and it is recommended that they are transfused within hours of collection. Adverse effects from granulocyte transfusions include fever, chills, respiratory symptoms, transfusion-transmitted infections, and the development of antibodies against human leukocyte antigens, which can interfere with subsequent transfusions.

Granulocytes are cells in the innate immune system characterized by the presence of specific granules in their cytoplasm. Such granules distinguish them from the various agranulocytes. All myeloblastic granulocytes are polymorphonuclear, that is, they have varying shapes (morphology) of the nucleus (segmented, irregular; often lobed into three segments); and are referred to as polymorphonuclear leukocytes (PMN, PML, or PMNL). In common terms, polymorphonuclear granulocyte refers specifically to "neutrophil granulocytes", the most abundant of the granulocytes; the other types (eosinophils, basophils, and mast cells) have varying morphology. Granulocytes are produced via granulopoiesis in the bone marrow.