B-1 cells participate an important role in the immune response against microsporidiosis. Macrophages population increased significantly in infected BALB/c mice, but not in infected or non-infected BALB/c XID mice. Increase of T lymphocytes in BALB/c and BALB/c XID mice infected with E. cuniculi. Adoptive transfer of B-1 cells was unable to protect BALB/c XID mice of E. cuniculi infection.