AIF1 and oligodendroglioma: Immunohistochemistry for Iba1, CD3, and CD20 was performed on treatment-naïve canine astrocytomas (n = 9) and oligodendrogliomas (n = 10) to determine the density and distribution of macrophages (Iba1) and infiltrating T (CD3) and B lymphocytes (CD20) within the tumor microenvironment [Figure 2A, C and E].