Immunohistochemical characterization of macrophage and dendritic cell subpopulations of the spleen, thymus, tongue and heart in cyclophosphamide-induced immunosuppressed rat

Resident cardiac macrophages: crucial modulators of cardiac (patho)physiology

Resident cardiac macrophages (rcMacs) are integral components of the myocardium where they have key roles for tissue homeostasis and in response to inflammation, tissue injury and remodelling. In this review, we summarize the current knowledge and limitations associated with the rcMacs studies. We describe their specific role and contribution in various processes such as electrical conduction, efferocytosis, inflammation, tissue development, remodelling and regeneration in both the healthy and the disease state. We also outline research challenges and technical complications associated with rcMac research. Recent technological developments and contemporary immunological techniques are now offering new opportunities to investigate the separate contribution of rcMac in respect to recruited monocytes and other cardiac cells. Finally, we discuss new therapeutic strategies, such as drugs or non-coding RNAs, which can influence rcMac phenotype and their response to inflammation. These novel approaches will allow for a deeper understanding of this cardiac endogenous cell type and might lead to the development of more specific and effective therapeutic strategies to boost the heart's intrinsic reparative capacity.

Histochemical and molecular overview of the thymus as site for T-cells development

The thymus represents the primary site for T cell lymphopoiesis, providing a coordinated set for critical factors to induce and support lineage commitment, differentiation and survival of thymus-seeding cells. One irrefutable fact is that the presence of non-lymphoid cells through the thymic parenchyma serves to provide coordinated migration and differentiation of T lymphocytes. Moreover, the link between foetal development and normal anatomy has been stressed in this review. Regarding thymic embryology, its epithelium is derived from the embryonic endodermal layer, with possible contributions from the ectoderm. A series of differentiating steps is essential, each of which must be completed in order to provide the optimum environment for thymic development and function. The second part of this article is focused on thymic T-cell development and differentiation, which is a stepwise process, mediated by a variety of stromal cells in different regions of the organ. It depends strongly on the thymic microenvironment, a cellular network formed by epithelial cells, macrophages, dendritic cells and fibroblasts, that provide the combination of cellular interactions, cytokines and chemokines to induce thymocyte precursors for the generation of functional T cells. The mediators of this process are not well defined but it has been demonstrated that some interactions are under neuroendocrine control. Moreover, some studies pointed out that reciprocal signals from developing T cells also are essential for establishment and maintenance of the thymic microenvironment. Finally, we have also highlighted the heterogeneity of the lymphoid, non-lymphoid components and the multi-phasic steps of thymic differentiation. In conclusion, this review contributes to an understanding of the complex mechanisms in which the foetal and postnatal thymus is involved. This could be a prerequisite for developing new therapies specifically aimed to overcome immunological defects, linked or not-linked to aging.

[Evaluation of splenic function by dynamic gammagraphy, study of pitted erythrocytes and submembranous vacuoles in patients with slight and severe splenic trauma receiving conservative treatment or splenectomy]

BACKGROUND AND OBJECTIVE

The splenic function of patients followed by the Department of General and Digestive Surgery in the Hospital Universitari Germans Trias i Pujol (HUGTiP) from 1985 to 2003 for different degrees of splenic trauma according to the classification of the American Association for the Surgery of Trauma (AAST) 1994 was quantified and related to the treatment received (non surgical, total splenectomy with or without splenosis and splenectomy plus autotransplantation) to detect splenic dysfunction predisposing the development of postsplenectomy sepsis (PSS).

PATIENTS AND METHOD

43 patients underwent an isotopic study with dynamic splenic gammagraphy and pitted erythrocytes (Normarsky optics) and submembranous vacuoles (transmission electron microscopy) were evaluated.

RESULTS

The non surgical group presented normal phagocytic and filtration function with the median speed of splenic enhancement being 3.46 Kcts/s2 (interval: 0.8-6.98). The percentage of pitted erythrocytes was 2% (0-8.8), the number of pits per erythrocyte was 0.03 (0-0.12) and the percentage of erythrocytes with 1, 2, 3 and 4 pits was 1.6%, 0.4%, 0% and 0%, respectively. The percentage of red cells with submembranous vacuoles was 2.55% (0-5.6), the number of vacuoles per red cell was 0.03 (0-0.06) and the percentage of red cells with 1, 2, 3 and 4 vacuoles was 2%, 0.2%, 0% and 0%, respectively. In the operated group, the splenic enhancement speed was 0.08 Kcts/s2 (0-1.75) (p < 0.0001). The percentage of pitted erythrocytes was 38% (0.2-64) (p < 0.0001), the number of pits per erythrocyte was 0.86 (0-1.8) (p < 0.0001) and the percentage of erythrocytes with 1,2,3 and 4 pits was 16.39%, 7.2%, 3.59% and 2.52%, respectively (p < 0.0001). The percentage of red cells with submembranous vacuoles was 11.2% (1.8-31.9) (p = 0.0006); the number of vacuoles per cell was 0.16 (p = 0.0022) and the percentage of red cells with 1, 2, 3 and 4 vacuoles was 6.51%, 1.73%, 0.4% and 0.2%, respectively (p = 0.0246, 0.0010, < 0.0001 and 0.0002, respectively).

CONCLUSIONS

Splenic function of patients with a history of splenic trauma receiving conservative treatment is normal, independently of the degree of the lesion, thereby reinforcing the use of this therapeutic approach to avoid the development of postsplenectomy sepsis. In the patients treated with splenectomy, with or without splenosis, splenic function was absent or very altered being partially conserved in cases treated with splenectomy plus autotransplantation.

AM-3K, an anti-macrophage antibody, recognizes CD163, a molecule associated with an anti-inflammatory macrophage phenotype

CD163 is a member of the scavenger receptor cysteine-rich superfamily restricted to the monocyte/macrophage lineage and is thought to be a useful marker for anti-inflammatory or alternatively activated macrophages. In this study we used mass spectrometric analysis to determine that the antigen recognized by the antibody AM-3K, which we previously generated as a tissue macrophage-specific monoclonal antibody, was CD163. An anti-inflammatory subtype of macrophages stimulated by dexamethasone or interleukin-10 showed strong reactivity for AM-3K and increased expression of CD163 mRNA. Immunohistochemical staining of routinely processed pathological specimens revealed that AM-3K recognized a specialized subpopulation of macrophages. In granulomatous diseases such as tuberculosis, sarcoidosis, or foreign body reactions, tissue macrophages around granulomas, but not component cells of the granulomas such as epithelioid cells and multinucleated giant cells, showed positive staining for AM-3K. In atherosclerotic lesions, scattered macrophages in diffuse intimal lesions were strongly positive for AM-3K, whereas foamy macrophages in atheromatous plaques demonstrated only weak staining. We therefore suggest that, in routine pathological specimens, AM-3K is a useful marker for anti-inflammatory macrophages because these cells can be distinguished from inflammatory or classically activated macrophages. Because AM-3K cross-reacts with macrophage subpopulations in different animal species including rats, guinea pigs, rabbits, cats, dogs, goats, pigs, bovine species, horses, monkeys, and cetaceans, it will have wide application for detection of CD163 in various animals.

Upregulation of receptor activator of nuclear factor-kappaB ligand expression in the thymic subcapsular, paraseptal, perivascular, and medullary epithelial cells during thymus regeneration

The receptor activator of nuclear factor (NF)-kappaB ligand (RANKL; also termed TRANCE/OPGL/ODF/TNFSF11), a new member of the tumor-necrosis factor (TNF) superfamily, was identified as a key cytokine involved in the differentiation of the immune system and the regulation of immunity as well as in bone metabolism. In particular, RANKL-deficient mice showed defects in the early differentiation of T lymphocytes, suggesting that RANKL is a novel regulator of early thymocyte development. Here, we describe the expression of RANKL during regeneration following acute involution induced by cyclophosphamide in the rat thymus. The present study demonstrates the presence and upregulated expression of the RANKL in thymic subcapsular, paraseptal, perivascular, and medullary epithelial cells during thymus regeneration. Our results suggest that the RANKL expressed in these thymic epithelial cells plays a role in the development of T cells during thymic regeneration.

Dendritic Cell Differentiation and Maturation in Embryonic Rat Liver: Immunohistochemistry and Electron Microscopy with Reference to Dendritic Cell Contacts

This study investigated the dendritic cell (DC) differentiation in embryonic rat liver utilizing in situ ultrastructural characterization and immunohistochemistry. The study revealed the existence of DCs early in hepatic ontogeny with positive immune staining to the OX-62 monoclonal antibody. DCs existed in three differentiating stages: immature, mature and transitional forms in between. At 14 and 16 days of gestation, immature and transitional forms of DCs dominated. Mature cells increased significantly in number through late gestational days (18 days onwards). DCs (particularly mature and moderate mature forms) revealed signs of active phagocytosis manifested by the existence of cytoplasmic phagosomes and heterophagosomes. At 18 days of gestation as well as newborn liver mature DCs displayed two distinct morphological phenotypes according to the degree of development of either the smooth endoplasmic reticulum or the lysosomal compartment. Mature DCs delineated close appositions to other DCs, hepatocytes, and clustering with lymphocytes especially through their cellular processes. The features of phagocytosis and DC-T-cell contacts may signify a role of DCs in immune surveillance in the embryonic liver.

Thymus cell-cell interactions

The recent advances in molecular biology and genetics, as well as the progress of in vitro techniques, have provided a more coherent image of the thymic function on the molecular level. But they have shifted the attention away from studies on the cellular level, which are necessary to clarify the biological roles of different cell types of the thymic microenvironment. The structure and function of the normal thymus depend on mutual interactions between thymocytes and nonlymphocyte cells. In this review a detailed description of morphological and phenotypic features of both maturing thymocytes and nonlymphocyte cells is given. The recent genetic and biochemical data are presented in conjunction with cytological results to enlighten the thymus cell-cell interactions during thymopoiesis and organization of thymic microstructure. Special emphasis is put on the experimental approaches, which may be used to study the interactions between thymocytes and nonlymphocyte cells in vivo.