Heterogeneity of Mouse Thymic Macrophages: I. Immunohistochemical Analysis.

Abstract

Summary. As the first step toward understanding the identity and functions of thymic macrophages in situ, we examined the phenotypic heterogeneity of mouse thymic macrophages in tissue sections by the immunohistochemical double staining method with four monoclonal antibodies (F4/80, Mac-2, anti-CD32/16 and anti-I-A antibodies) as macrophage markers. Morphologically, three types of macrophages were identified: dendritic, round and flat-shaped. Dendritic macrophages were scattered throughout the thymus, and most of them were stained by all four markers. Among these macrophages, those at the cortico-medullary region (CMR) expressed a high intensity of CD32/16 antigen. Round macrophages were also distributed throughout the thymus; most of them, however, were localized in the cortico-medullary region to the medulla. These cells were F4/80-negative, Mac-2-positive, CD32/ 16-negative and I-A-positive. In contrast, round macrophages located at the cortex expressed F4/80. Flatshaped macrophages were localized at the subcapsular region of the cortex where active lymphopoiesis was observed. This type was positive for F4/80 and CD32/16, but negative for Mac-2. Furthermore, most of the three types of thymic macrophages showed intense reactions of the I-A antigen within the cytoplasm in addition to the expression of I-A antigen on the cell membrane. These results indicate that morphological characteristics of thymic macrophages at different locations reflect phenotypic variations detected in immunohistochemistry, and suggest that these different type macrophages may play distinct roles at various locations in thymocyte development in the thymus.

Neutrophils Accelerate Macrophage-Mediated Digestion of Apoptotic Cells In Vivo as Well as In Vitro

“…Histological analysis of thymi until 10.5 h after whole-body x-irradiation revealed many apoptotic cell clusters in the cortex without F4/80 signals and no free, single apoptotic cells, suggesting that the clusters are not phagocytosed by macrophages. As Soga et al (53) reported, there are three morphologically distinct types of macrophages, namely dendritic, round, and flat types, in the thymus. Dendritic type macrophages are distributed throughout the thymus, and most of them are positive for F4/80 Ag.…”

“…Roundtype macrophages localized in the corticomedullary region and medulla are negative for F4/80, whereas round-type macrophages localized in the cortex express F4/80. Flat-type macrophages are localized in the subcapsular region of the cortex, and they are positive for F4/80 (53). In brief, all types of macrophages in the cortex are positive for F4/80.…”

Age‐dependent changes in thymic macrophages and dendritic cells

“…Most cortical and medullary macrophages can be detected, nevertheless, by expression of CD68, ED1, and F4/80 cell markers Brekelmans and van Ewijk, 1990;Soga et al, 1997;Vicente et al, 1995). Their origin has not been well established yet.…”

Thymic Expression of the Pancreatic Endocrine Hormones

“…The anatomical, morphological and functional characteristics of these cells vary greatly and depend on the environment in which they seed [29,30]. In the thymus, macrophages have two major functional roles: phagocytosis of apoptotic lymphocytes (immature T cells which are unable to develop further) and to a lesser extent antigen presentation to developing lymphocytes [3,[31][32][33]. The majority of thymic macrophages are located in the cortex and corticomedullary region of the thymus.…”