CellaQuant(TM) Human IL-4 (Interleukin 4) ELISA Kit

Interleukin-4 (IL-4) is a pleiotropic type I cytokine, predominantly produced by activated Th2 cells, with additional sources including mast cells, basophils, eosinophils, and innate lymphoid cells (ILC2s). It is a helical-bundle protein that signals through two distinct receptor complexes: the type I receptor (IL-4Ralpha/common gamma chain) expressed on hematopoietic cells, and the type II receptor (IL-4Ralpha/IL-13Ralpha1) expressed on non-hematopoietic cells.IL-4 is a central regulator of type 2 immunity, orchestrating Th2 cell differentiation, IgE class switching in B cells, and the alternative (M2) activation of macrophages. It also promotes mast cell and eosinophil proliferation, upregulates adhesion molecules on endothelium, and suppresses pro-inflammatory Th1 and Th17 responses. These actions position it as a key player in allergic diseases such as asthma, atopic dermatitis, and allergic rhinitis, as well as in parasitic infection control and tissue repair. Protein function: Cytokine secreted primarily by mast cells, T-cells, eosinophils, and basophils that plays a role in regulating antibody production, hematopoiesis and inflammation, and the development of effector T-cell responses (PubMed:1993171, PubMed:3016727). Induces the expression of class II MHC molecules on resting B-cells. Enhances both secretion and cell surface expression of IgE and IgG1 (PubMed:1993171). Also regulates the expression of the low affinity Fc receptor for IgE (CD23) on both lymphocytes and monocytes (PubMed:2521231). Positively regulates IL31RA expression in macrophages. Stimulates autophagy in dendritic cells by interfering with mTORC1 signaling and through the induction of RUFY4. In addition, plays a critical role in higher functions of the normal brain, such as memory and learning (By similarity). Upon binding to IL4, IL4R receptor dimerizes either with the common IL2R gamma chain/IL2RG to produce the type 1 signaling complex, located mainly on hematopoietic cells, or with the IL13RA1 to produce the type 2 complex, which is also expressed on nonhematopoietic cells (PubMed:10219247, PubMed:11526337, PubMed:18243101). Engagement of both types of receptors initiates JAK3 and to a lower extend JAK1 phosphorylation leading to activation of the signal transducer and activator of transcription 6/STAT6 (PubMed:7721895) [The UniProt Consortium]