|Cell Proliferation Induced by IL‑4 and Neutralization by Feline IL‑4 Antibody. Recombinant Feline IL‑4 (Catalog # 984-FL) stimulates proliferation in the TF‑1 human erythroleukemic cell line in a dose-dependent manner (orange line). Proliferation elicited by Recombinant Feline IL‑4 (100 ng/mL) is neutralized (green line) by increasing concentrations of Mouse Anti-Feline IL‑4 Monoclonal Antibody (Catalog # MAB984). The ND50 is typically 1-4 µg/mL.|
Interleukin-4 (IL-4), also known as B cell-stimulatory factor-1, is a monomeric, approximately 13‑18 kDa Th2 cytokine that shows pleiotropic effects during immune responses (1‑3). It is a glycosylated polypeptide that contains three intrachain disulfide bridges and adopts a bundled four alpha -helix structure (4). Feline IL-4 is synthesized with a 24 amino acid (aa) signal sequence. Mature feline IL-4 shares 81%, 64%, 49%, 40%, and 40% aa sequence identity with canine, bovine, human, mouse, and rat IL-4, respectively. Human IL-4 is active on feline dendritic cells (5). IL-4 exerts its effects through two receptor complexes (6, 7). The type I receptor, which is expressed on hematopoietic cells, is a heterodimer of the ligand binding IL-4 R alpha and the common gamma chain (a shared subunit of the receptors for IL-2, -7, -9,-15, and -21). The type II receptor on nonhematopoietic cells consists of IL-4 R alpha and IL-13 R alpha 1. The type II receptor also transduces IL-13 mediated signals. IL-4 is primarily expressed by Th2-biased CD4+ T cells, mast cells, basophils, and eosinophils (1, 2). It promotes cell proliferation, survival, and immunoglobulin class switch to IgE in B cells, acquisition of the Th2 phenotype by naïve CD4+ T cells, priming and chemotaxis of mast cells, eosinophils, and basophils, and the proliferation and activation of epithelial cells (8‑11). IL-4 plays a dominant role in the development of allergic inflammation and asthma (10, 12).