The absence of eosinophils is associated with early metastatic lesions in Leishmania amazonensis-infected mice

BACKGROUND Eosinophils are granulocytes that rapidly increase frequency in the bloodstream during helminthic infections and allergic responses. They are found in tissue infected by Leishmania during early disease, but their role during infection is not entirely understood.OBJECTIVES We aim to compare the disease due to Leishmania amazonensis in BALB/c and <^>dbl-GATA1 mice, which lack eosinophils.METHODS BALB/c and <^>dbl-GATA1 mice infected with L. amazonensis were observed for several weeks. The parasite load and dissemination pattern were assessed.FINDINGS The <^>dbl-GATA1 mice developed an anticipated dissemination of L. amazonensis and a worsening disease. No differences were found in the lesion development or the parasite load in the footpad among <^>dbl-GATA1 mice and BALB/c eight weeks after infection. However , nine weeks after infection , massive growth of metastatic lesions appeared in several parts of the skin in <^>dbl-GATA1 mice , weeks earlier than BALB/c. We observed increased parasites in the bloodstream , probably an essential dissemination route. Thirteen weeks after infection, metastatic lesions were found in all <^>dbl-GATA1 mice.MAIN CONCLUSION These results suggest a protective role of eosinophils in delaying the disease caused by L. amazonensis, although several limitations of this mice strain must be considered.