Histiocytic and dendritic reticulum cells shown by a zinc iodide-osmium technique

Evidence for transepithelial dendritic cells in human H. pylori active gastritis

BACKGROUND

Despite extensive experimental investigation stressing the importance of bacterial interaction with dendritic cells (DCs), evidence regarding direct interaction of Helicobacter pylori or its virulence products with DCs in the human gastric mucosa is lacking.

METHODS

Human gastric mucosa biopsies, with or without H. pylori infection and active inflammation, were investigated at light and electron microscopy level with immunocytochemical tests for bacterial products (VacA, urease, outer membrane proteins) and DC markers (DC-SIGN, CD11c, CD83) or with the DC-labeling ZnI(2)-OsO(4 )technique. Parallel tests with cultured DCs were carried out.

RESULTS

Cells reproducing ultrastructural and cytochemical patterns of DCs were detected in the lamina propria and epithelium of heavily infected and inflamed (but not of normal) mucosa, where DC luminal endings directly contact H. pylori and take up their virulence products. Cytotoxic changes (mitochondrial swelling, cytoplasmic vacuolation, autophagy) were observed in intraepithelial DCs and reproduced in cultured DCs incubated with H. pylori broth culture filtrates to obtain intracellular accumulation of VacA and urease. Granulocytes were also seen to contact and heavily phagocytose luminal H. pylori, while macrophages remained confined to basal epithelium, though taking up bacteria and bacterial products.

CONCLUSION

Human DCs can enter H. pylori-infected gastric epithelium, in association with other innate immunity cells, to take up bacteria and their virulence products. This process is likely to be important for bacterial sensing and pertinent immune response; however, it may also generate DC cytotoxic changes potentially hampering their function.

Gross morphology and ultrastructure of dendritic cells in the normal human decidua

Five normal placentae of normal pregnancy and delivery were used to study the gross morphology and ultrastructure of the dendritic cells in the normal human decidua. Zinc iodide osmium (ZIO) mixture was prepared. Small pieces of the placenta were processed for light microscopy and electron microscopy. For light microscopy, the small pieces of placenta were incubated in 20 mM PBS-EDTA solution, ph 7.4 at 37 degrees C to detach the basal plate. The basal plate pieces were incubated in ZIO. A wholemount preparation of the basal plate demonstrated the whole profile and gross morphology of the dendritic cell. For electron microscopy, the placenta pieces were fixed in 3% glutaraldehyde in 0.1 M phosphate buffer, ph 7.4, washed with phosphate buffer, put in ZIO mixture, washed in distilled water, dehydrated in graded ethanol, cleared in propylene oxide, and embedded in resin. Ultra thin sections of the ZIO blocks were cut using a diamond knife and stained with lead citrate. Ultrastructure of the dendritic cell presented multiple cytoplasmic processes, lobulated or round or oval, heterochromatic or euchromatic nucleus, mitochondria, free ribosomes, and pieces of rough endoplasmic reticulum, but no Birbeck granules.

Stromal cell organisation in the mouse lymph node. A light and electron microscopic investigation using the zinc iodide-osmium technique

The organisation of the stromal cell compartment in the mouse lymph node was studied by light and electron microscopy after tissue impregnation by the zinc iodide-osmium (ZIO) method. Fibroblastic reticular cells (FRCs) represented the main stromal cell population. These cells were located both in the cortical region and in the medulla and exhibited various configurations. In the cortex, FRCs were fusiform in shape and came into close proximity with the floor of the subcapsular sinus. In the medulla, the FRCs were shaped like irregular dendritic cells which formed a complex 3-dimensional network. The FRCs surrounded vascular structures such as capillaries and/or high endothelial venules; in these instances they were organised in a discontinuous sheath-like fashion around the vessel wall. By light and electron microscopy, FRCs have been observed to come in close spatial relationship with a number of cells in the lymph node, including sinus endothelial cells, the endothelium of high endothelial venules and capillaries, various types of lymphocytes, follicular dendritic cells and interdigitating cells. These microanatomical features are consistent with the proposal that FRCs may be involved in the communicative networks between the different lymph node compartments. In particular, the FRCs may be involved in the transport of molecules from the sinus compartment to the high endothelial venules or to the distinct cell populations in the lymphoid parenchyma.

New applications for the zinc iodide-osmium tetroxide technique

The zinc iodide-osmium tetroxide (ZIO) fixation/staining method was applied for neurocytological studies and also to examine several other tissue samples including epidermal Langerhans cells, blood and bone marrow cells and lymphoid tissue. Although precise specificity cannot be attributed to the staining reaction, interesting staining patterns for different cell types were observed by using one of the ZIO staining solutions. The significance of ZIO positivity is briefly discussed.

Immunohistochemical demonstration of S-100 protein antigen-containing cells in chronic cutaneous leishmaniasis

The presence and distribution of S-100 protein antigen and lysozyme were investigated by the immunoperoxidase method in paraffin sections of 13 cases of chronic cutaneous leishmaniasis from Saudi Arabia. Varying numbers of S-100+lys- histiocytic reticulum cells were found in the dense inflammatory infiltrate in 11 out of 13 cases. These cells were considerably more numerous in the lesions dominated by cells of the mononuclear phagocytic system and granulomata than in the cases with plasma cellular or lymphocytic predominance. Activated lys+ macrophages, epithelioid cells, and multinucleated giant cells were always S-100-. Around the granulomata several S-100+lys- histiocytic reticulum cells could be found. These findings suggest that antigen-presenting cells are present in the inflammatory infiltrate of cutaneous leishmaniasis.