Because macrophages are known to express membrane-bound Fgl2 as well as sFgl2, the ability of macrophages to secrete sFgl2 (which binds to FcγRIIB) was assessed through isolation of CD11b+ cells from naive spleen, tumor-challenged spleen, or tumor of WT mice (Figure 6, F and G). Here, FGL2 is linked to neoplasm.