|Cell Proliferation Induced by IL‑5 and Neutralization by Equine IL‑5 Antibody. Recombinant Equine IL‑5 (Catalog # 2470-EL) stimulates proliferation in the TF‑1 human erythroleukemic cell line in a dose-dependent manner (orange line). Proliferation elicited by Recombinant Equine IL‑5 (50 ng/mL) is neutralized (green line) by increasing concentrations of Goat Anti-Equine IL‑5 Antigen Affinity-purified Polyclonal Antibody (Catalog # AF2470). The ND50 is typically 0.5-2.0 µg/mL.|
|IL‑5 in Equine PBMCs. IL‑5 was detected in immersion fixed equine peripheral blood mononuclear cells (PBMCs) treated with calcium ionomycin and PMA using Goat Anti-Equine IL‑5 Antigen Affinity-purified Polyclonal Antibody (Catalog # AF2470) at 15 µg/mL for 3 hours at room temperature. Cells were stained using the NorthernLights™ 557-conjugated Anti-Goat IgG Secondary Antibody (red; Catalog # NL001) and counterstained with DAPI (blue). Specific staining was localized to cytoplasm. View our protocol for Fluorescent ICC Staining of Non-adherent Cells.|
Interleukin-5 (IL-5) is a 40 kDa, secreted, heparin-binding, disulfide-linked homodimeric glycoprotein that belongs to the alpha -helical group of cytokines (1‑3). IL-5 is primarily produced by CD4+ Th2 cells, but other cell types such as eosinophils, endothelial cells, mast cells, visceral (airway) smooth muscle cells, bronchial epithelium, CD16+ NK cells and gamma δ T cells can also produce IL-5. Equine IL-5 is synthesized as a 134 amino acid (aa) precursor that contains a 19 aa signal sequence and a 115 aa mature segment. There are four alpha -helices, two potential N-linked glycosylation sites, and two cysteines that form interchain disulfide bonds with a second, antiparallel IL-5 molecule (3, 4). While human and mouse IL-5 have a potential NLS in their sequence, it is unclear if equine IL-5 has such a sequence. Mature horse IL-5 shares 71%, 89%, 88%, 83%, 66% and 63% aa sequence identity with mature human, bovine, feline, canine, mouse and rat IL-5, respectively.
The receptor for IL-5 consists of a 60 kDa ligand-binding subunit (IL‑5 R alpha ) and a 120 kDa signal-transducing subunit ( beta c). It is suggested that dimeric IL-5 binding to
IL‑5 R alpha recruits beta c, which subsequently covalently links with IL‑5 R alpha. This trimeric complex then associates with another trimeric complex to form the physiologic IL-5 receptor (6). Following binding, IL-5 has targeted effects. It promotes the maturation and migration of eosinophils, partially through the effects of eotaxin. It mobilizes eosinophils and CD34+ progenitors from marrow. It also enhances Ig release from B cells and contributes to IL-4 production. Finally, it primes basophils for histamine and leukotriene release (1, 2, 7).