The role of Toll-like receptors and C-type lectins for vaccination against Candida albicans

Recent progress has provided important novel insights in the processes driving the adaptive immune responses. Central to these developments is the discovery of pattern recognition receptors like TLRs and CLRs that not only induce innate immune responses, but also modulate cellular and humoral adaptive immunity. As vaccination is one of the great achievements in medicine and probably the most powerful tool to protect human and animals against infectious disease, further vaccine development and optimization of current strategies can improve health status of large groups of people. Development of a vaccine against Candida spp. should induce both cellular and humoral immune responses. While the TLRs are strong inducers of inflammatory responses, it seems that the CLRs have the potential to modulate these responses by enhancement or inhibition of cytokine production. Understanding the natural host defense mechanisms against pathogens like C. albicans therefore helps to identify the proper targets for inducing a strong adjuvant effect, in order to stimulate an effective adaptive immune response and protection.     

Exogenous gonadotropin administration affects the glycocalyx of rat endometrial epithelial cells during the period of implantation

Purpose Exogenous gonadotropins which cause superovulation are known to effect endometrial morphology, including the glycocalyx of surface epithelial cells. Certain of the carbohydrates in the glycocalyx of surface epithelial cells may be involved in the attachment and implantation of the blastocyst.Methods The effect of exogenous gonadotropins on specific carbohydrates in the glycocalyx of the rat endometrium around the time of implantation was investigated. Lectin-avidin-biotin-ferritin cytochemistry was used to ascertain which carbohydrates were affected. The lectins soybean agglutinin, fucose binding protein and wheat germ agglutinin were used.Results Statistically significantly less lectin was associated with the apical membrane of surface epithelial cells of animals following hyper stimulation than in noninjected pregnant animals.Conclusions The reduction in the carbohydrates contributes to a reduced receptivity of the endometrium for the blastocyst.     

Analysis of tumour necrosis factora-specific,lactose-specific and mistletoe lectin-specific binding sites in human lung carcinomas by labelled ligands

Summary Receptor sites can be visualized by labelled ligands as an alternative to receptor-specific antibodies, as substantiated for two different receptor classes. Recombinant tumour necrosis factor (TNF) was biotinylated via amino-groups and the resultant probe was applied to formalin-fixed, paraffin-embedded tissue sections of 94 primary bronchial carcinomas and to normal peripheral lung parenchyma. In addition, monoclonal antibodies specific for neuron-specific enolase (NSE) and TNF itself were used. The biotinylated -galacto-side-specific mistletoe lectin, which exhibits dose-dependent immunomodulatory and toxic potency, and two probes that specifically detect certain types of sugar receptors were employed to illustrate further the feasibility of using ligands for receptor localisation. The tumours comprised 62 small cell lung carcinomas, 10 epidermoid carcinomas, 11 adenocarcinomas and 11 large cell anaplastic carcinomas. Expression of TNF-binding sites was found in 39 of the small cell lung carcinomas and in 13 of the non-small cell lung carcinomas. Binding capacity for the TNF-specific antibody was seen in similar proportions of small cell lung carcinomas and of non-small cell lung carcinomas. None of the normal lung parenchymas revealed significant staining. Binding capacities to mistletoe lectin were seen in all normal lung parenchymas and in nearly all cases of adenocarcinoma (10/11). A correlation between the expression of NSE and the binding capacities to TNF was detected. Endogenous lectins, specific for lactose or-GalNAc, were displayed in nearly one half of the small cell lung carcinoma cases (44% or 45% respectively) and in about 25% of the non-small cell lung carcinoma cases.     

Identification of the reactive subunits of Aspergillus umbrosus involved in the antigenic response in farmer's lung

Background Farmer's lung (FL) is the most common form of extrinsic allergic alveolitis and the fungus Aspergillus umbrosus has frequently been associated with FL among Finnish farmers. IgG and IgA class antibodies against Aspergillus umbrosus are found in the serum of FL patients and healthy exposed farmers. So far the immunologically reactive subunits of Aspergillus umbrosus are unknown. Objectives The purpose of the study was to identify and localize the reactive subunits of Aspergillus umbrosus that are involved in the antigenic response in FL. Methods The distribution of the primary antibody on the outer wall layers of 4- and 11 day-old fungi Aspergillus umbrosus was studied by pre-embedding immunolabelling with fluorescein isothiocyanate (FITC)- and gold-conjugated antibodies. The surface carbohydrates of the outer wall layers were studied using FITC-conjugated lectins. Results FITC-conjugated antibodies from FL patient sera reacted with spores (conidia), phialides and hyphae, whereas the fruiting body, cleistothecia, remained unstainable. Immunofluorescence labelling was confirmed by immunolabelling electron microscopy, and gold-conjugated IgG antibodies were found on the outer cell walls of spinulose conidia, and in a less degree on the outer cell walls of hyphae and phialides. Only single gold particles were found scattered on the surfaces of cleistothecia. The surface carbohydrates of Aspergillus umbrosus conidia. vesicles, phialides and hyphae had a high affinity to GlcNAcβl- and Manαl-/Glcαl- specific lectins and only GlcNAcβl-specific lectins also reacted with the outer cell walls of cleistothecia. Blocking of the antigenic sites of Aspergillus umbrosus by preincubating antigen-coated enzyme linked immunosorbent assay (FLISA) plates with lectins caused some inhibition, indicating that sites with the highest affinity for lectins were not always antigenic sites. Conclusion Gold- and FITC-conjugated antibodies were distributed mostly on the outer wall layers of conidia, hyphae and phialides of Aspergillus umbrosus and GlcN Acβl -linked lectins had the strongest affinity to the outer wall layers.     

The target antigens of naturally occurring human anti-beta-galactose IgG are cryptic on porcine aortic endothelial cells

Abstract: The identification of the xeno‐antigens/xeno‐antibodies combinations involved in pig‐to‐human xenograft rejection is an essential step for understanding this process and for the development of procedures to prevent it. Although it is widely accepted that the terminal disaccharide Galα1,3Gal‐R is by far the major epitope recognized by human natural antibodies reactive with pig tissues, there is also evidence that other carbohydrates epitopes might be important in xenograft rejection.
In an attempt to further improve our knowledge of the repertoire of human natural antibodies with anti‐pig specificity we sought to determine whether naturally occurring human anti‐β‐galactose IgG could interact with porcine aortic endothelial cells (PAEC). Histochemical analysis of porcine aorta sections revealed that the carbohydrate structures recognized by the anti‐β‐galalactose IgG are present on endothelial cells but in a cryptic form that can be unmasked by sialidase treatment. These structures were also found to be cryptic in cultured PAEC. In addition we demonstrated that PAEC may adsorb fetal calf serum (FCS) glycoproteins when cultured in FCS‐supplemented medium, a process susceptible to generating artifactual observations in carbohydrate antigens analysis.
In conclusion, despite their abundance, human anti‐β‐galactose IgG do not represent a primary concern in pig‐to‐human xenotransplantation as the carbohydrate structures to which they bind are normally masked by sialic acid residues on porcine endothelial cells. However, whether these cryptic epitopes might be exposed on endothelial cells from genetically engineered animals should be further investigated because, if so, additional approaches will be needed to suppress their interaction with human anti‐β‐galactose IgG.     

SPECIFICITY OF HEMATOPOIETIC STEM CELL HOMING

Homing of hematopoietic stem cells (HSC) may be defined as the cells’ ability to seek marrow stroma selectively, to interact with it and subsequently to lodge within it to initiate hematopoiesis. This complex process is no doubt mediated through multiple recognition/adhesion events. Homing may proceed through one of several alternative mechanisms, however, such as through physical trapping of stem cells by marrow ultrastructural elements or through the providing of a selective survival and/or proliferative advantage by marrow. A third alternative that provides for the central element of stem cell homing—its high degree of specificity—is through the action of a specific homing protein in HSC. There are data to support this latter mechanism of stem cell homing as the correct one, and the nature of this protein may be similar to that of the lymphocyte homing receptors that are lectin-like molecules. Lectin–carbohydrate interactions are known to provide enormous specificity to cell recognition processes and to participate in cellular targeting. Leukemic cells have recently been demonstrated to home to marrow stroma and proliferate in the same way as normal stem cells. Thus, identification of proteins or other adhesion molecules that participate in normal and malignant cell homing could lead to more specific recruitment regimens for tumour-free collections.