Interleukin 13 (IL-13) is located on chromosome 5q31 with a length of 1.4kb. IL-13 and IL-4 exhibit a 30% of sequence similarity and have a similar structure. IL-13 is cytokine secreted by many cell types, but especially T helper type 2 (Th2) cells. IL-13 has effects on immune cells that are similar to those of the closely related cytokine IL-4. Although IL-13 is associated primarily with the induction of airway disease, it also has anti-inflammatory properties. IL-13 is known to induce changes in hematopoietic cells, but these effects are probably less important than that of IL-4. IL-13 induces its effects through a multi-subunit receptor that includes the alpha chain of the IL-4 receptor (IL-4Rα) and at least one of two known IL-13-specific binding chains.
IL-13 specifically induces physiological changes in parasitized organs that are required to expel the offending organisms or their products. IL-13 induces many features of allergic lung disease, including airway hyperresponsiveness, goblet cellmetaplasia and mucus hypersecretion, which all contribute to airway obstruction. Furthermore, IL-13 inhibits HIV-1 replication in primary culture-derived macrophages and represents a candidate cytokine for the suppression of HIV infection within monocytes and macrophages in vivo.