Immunohistochemical Study of M1 and M2 Macrophages Population in Chronic Villitis of the Placenta

Abstract Introduction Villitis is characterized by the presence of inflammatory infiltrate (CD8 lymphocyte) in the placental villous and is classified as to the etiology in known and unknown. In most cases, villitis is idiopathic (villitis of unknown etiology [VUE]) because no microorganisms are evident and there are no maternal symptoms or signs. It has recently been proposed that pregnancy is, in fact, an active and highly regulated immune process in which macrophages play an important role. Macrophages may present with M1 phenotype, important effector cells, or M2 phenotype, capable of suppressing the function of M1 macrophages and influencing immunoregulation and tissue repair. CD68 antibody recognizes macrophages M1 and M2, whereas CD11c and CD163 antibodies are specific for the identification only of M1 and M2 macrophages, respectively. The objective of our study is to characterize in human placentas in the subpopulation of M1 and M2 macrophages in VUE. Methods Sixteen cases of chronic villitis (all without an identifiable etiologic agent) and three control placentas were examined using immunohistochemistry with antibodies for CD68, CD11c, CD163, and CD3. Results CD68 and CD163 were present in all cases in the normal areas. CD68, CD163, and CD11c were present in the villous stroma and in the intervillous space in the inflamed areas. The percentage of CD68-positive macrophages was higher than CD163- and CD11c-positive macrophages in all specimens studied. A total increase of CD68, CD163, and CD11c with the predominance of CD11c over CD163 in the inflamed areas was observed. Conclusion The predominance of M1 macrophages (CD11c) in the inflamed areas suggests the influence of these cells in the pathogenesis VUE. The higher amount of M2 (CD163) in the inflamed villous compared to normal areas suggests a possible immunoregulatory mechanism of the inflammatory process in VUE.