THE ROLE OF INTERLEUKIN-5 (IL-5) IN-VIVO - STUDIES WITH IL-5 DEFICIENT MICE

Eosinophil recruitment is a characteristic feature of a number of path ological conditions and was the topic of the recent International Symp osium on allergic inflammation, asthma, parasitic and infectious disea ses (Rio de Janeiro, June 3-5, 1996). Since interleukin-5 (IL-5) is be lieved to regulate the growth, differentiation and activation of eosin ophils (Coffman et al. 1989, Sanderson 1992), the role of eosinophils and IL-5 are closely linked. Although IL-5 specifically regulates eosi nophilia in vivo and this is its most well established activity, it is becoming clear that IL-5 also has other biological effects. The recen t derivation of an IL-5 deficient mouse (Kopf et al. 1996), provides a model for exploring not only the role of IL-5 and eosinophils but als o other novel activities of IL-5. Of note is that although the IL-5 de ficient mice cannot elicit a pronounced eosinophilia in response to in flammatory stimulation following aeroallergen challenge or parasite in fection they still produce basal levels of eosinophils that appear to be morphologically and functionally normal. However, the basal levels of eosinophils appear insufficient for normal host defence as IL-5 def iciency has now been shown to compromise defence against several helmi nth infections. In addition, IL-5 deficient mice appear to have functi onal deficiencies in B-I B lymphocytes and in IgA production.