IL-5 DRIVES EOSINOPHILS FROM BONE-MARROW TO BLOOD AND TISSUES IN A GUINEA-PIG MODEL OF VISCERAL LARVA MIGRANS SYNDROME

This study was undertaken to evaluate the role of IL-5 in eosinophil m igration and in the maintenance of eosinophilia in a guinea-pig model of visceral larva migrans syndrome. The results show that the infectio n of animals with Toxocara canis induced an early increase in serum IL -5 levels that might be essential for eosinophil differentiation and p roliferation and for the development of eosinophilia When infected gui nea-pigs were treated with mAb anti-IL-5 (TRFK-5) given at the same ti me or 1 or 3 days after infection, there was a high percentage of redu ction of eosinophil counts 18 days after infection However, when the m Ab was administered during the peak of eosinophilia, there was high in hibition in blood, no inhibition in bronchoalveolar lavage fluid (BALF ) or peritoneum and an increase in eosinophil numbers in bone marrow. Thus, a basic level of IL-5 may be essential to drive eosinophils from bone marrow to blood and tissues, and for the maintenance of eosinoph ilia in infected animals. We may also conclude that when eosinophils h ave already migrated to the lungs, TRFK-5 has no power to inhibit eosi nophilia, which is also under control of local lung cells producing IL -5. in this way, only one later TRFK-5 treatment may not be sufficient to modify the lung parenchyma microenvironment, since T. canis antige ns had already stimulated some cell populations to produce IL-5.