Recombinant Rhesus Macaque IL-5 Protein

Interleukin-5 (IL-5) is a secreted glycoprotein that belongs to the alpha-helical group of cytokines (1-3). Unlike other family members, it is present as a covalently linked antiparallel dimer (4, 5). Rhesus IL‑5 is synthesized as a 134 amino acid (aa) precursor that contains a 19 aa signal sequence and a 115 aa mature segment. Mature rhesus IL‑5 shares 98%, 95%, 70%, 71%, 66%, 70%, 61% and 64% aa sequence identity with mature human, mangabey, mouse, rat, feline, equine, canine and bovine IL-5, respectively. IL-5 is primarily produced by CD4⁺ Th2 cells, but also by activated eosinophils, mast cells, EBV-transformed B cells, Reed-Sternberg cells in Hodgkin’s disease, and IL‑2‑stimulated invariant natural killer T cells (iNKT) (1-3, 6-8). IL-5 increases production and mobilization of eosinophils and CD34⁺ progenitors from the bone marrow and causes maturation of eosinophil precursors outside the bone marrow (1, 6, 9, 10). The receptor for human IL-5, mainly expressed by eosinophils, but also found on basophils and mast cells, consists of a unique ligand-binding subunit (IL-5 R alpha) and a shared signal-transducing subunit, betac (3, 6, 11). IL‑5 R alpha first binds IL-5 at low affinity, then associates with preformed betac dimers, forming a high-affinity receptor (12). IL-5 also binds proteoglycans, potentially enhancing its activity (13). Soluble forms of IL‑5 R alpha  antagonize IL-5 and can be found in vivo (10, 14). In humans, IL-5 primarily affects cells of the eosinophilic lineage, and promotes their differentiation, maturation, activation, migration and survival, while in mice IL‑5 also enhances Ig class switching and release from B1 cells (1-3, 9, 10, 15, 16). IL-5 also promotes differentiation of basophils and primes them for histamine and leukotriene release (17).