Defence of mucous membranes by antibodies, receptor analogues and non-specific host factors

Some Immune Parameters of Term Newborns at Birth Are Associated with the Concentration of Iron, Copper and Magnesium in Maternal Serum

The nutritional status of pregnant women is considered to affect fetal development and the health condition of newborns, including their immune system. We investigated the relationship between the concentrations of magnesium (Mg), calcium (Ca), zinc (Zn), iron (Fe) and copper (Cu) in maternal serum (MS) and the concentrations of IgG antibodies and antineutrophil cytoplasmatic auto-antibodies against lactoferrin (Lf-ANCA) in umbilical cord serum (UCS). IgG was considered as a promoter of immunity, and Lf-ANCA as an inhibitor. The examined group consisted of 98 pregnant women and their healthy term newborn children. The concentrations of mineral elements were measured by FAAS/FAES, while the concentrations of antibodies were determined by ELISA. Excessive MS Fe and insufficient MS Cu were related to insufficient UCS IgG and excessive UCS Lf-ANCA. The correlation analysis showed confirming results. Adequate UCS IgG and Lf-ANCA were related to MS Mg at the strictly lower limit of the reference values. The results obtained seem to suggest that an excess of Fe and a deficiency of Cu in pregnancy may adversely affect some immune parameters of newborns. Reference values for MS Mg are likely to require reconsideration. It would be advisable to monitor the nutritional status of pregnant women with minerals in order to support the immune capacity of newborns.

Mechanisms of infectious diarrhea

Infectious diarrhea is an important public health problem worldwide. Research has provided new insights into the mechanisms of diarrhea caused by various pathogens that are classified as noninflammatory, inflammatory or invasive. These three groups of organisms cause two diarrheal syndromes--noninflammatory diarrhea and inflammatory diarrhea. The noninflammatory diarrheas are caused by enterotoxin-producing organisms such as Vibrio cholerae and enterotoxigenic Escherichia coli, or by viruses that adhere to the mucosa and disrupt the absorptive and/or secretory processes of the enterocyte without causing acute inflammation or mucosal destruction. Inflammatory diarrhea is caused by two groups of organisms--cytotoxin-producing, noninvasive bacteria (e.g. enteroaggregative Escherichia coli, enterohemorrhagic Escherichia coli and Clostridium difficile), or by invasive organisms (e.g. Salmonella spp., Shigella spp., Campylobacter spp., Entamoeba histolytica). The cytotoxin-producing organisms adhere to the mucosa, activate cytokines and stimulate the intestinal mucosa to release inflammatory mediators. Invasive organisms, which can also produce cytotoxins, invade the intestinal mucosa to induce an acute inflammatory reaction, involving the activation of cytokines and inflammatory mediators. Regardless of the underlying mechanism they use, these various types of pathogen have all successfully evolved to evade and modulate the host defense systems. The mechanisms by which the different pathogens invade the host and cause infectious diarrhea are the topic of this Review.

Bacterial adherence to mucosal epithelium in the upper airways has less significance than believed

BACKGROUND

Bacterial adherence to the upper airway epithelium is considered to be an important phenomenon in the pathogenesis of infections. However, the evidence for the hypothesis that bacterial adherence to mucosal epithelial cells has significance for pathogenesis of mucosal infections is based on studies using indirect techniques. We could find no biopsy studies with direct ocular observations of significant numbers of bacteria adhering to upper airway mucosal epithelial cells either in health or during disease.

RESULTS

We studied specimens from healthy and infected tonsillar epithelium and specimens from the soft palate epithelium obtained by surgery. The specimens were examined by TEM. In the vast majority of specimens, we found no bacteria adhering to the epithelial cells in the mucosal line regardless of whether the patient was infected or not. Bacteria adhering to shed epithelial cells were seen in higher numbers. Furthermore, as bacteria are small compared to epithelial cells, we calculated the risk of overlooking every adhered bacteria in a section if bacterial adherence was such a significant phenomenon as earlier suggested. We found this risk to be very small.

CONCLUSION

We conclude that bacterial adherence to mucosal surface epithelial cells is not a significant phenomenon, either in healthy mucosa in the upper airways or during infection. This is also in line with our earlier results, where we have shown that the site for the infectious process in pharyngotonsillitis is in the secretion on the tonsillar mucosal surface.

Expression profiling in knockout mice: lymphotoxin versus tumor necrosis factor in the maintenance of splenic microarchitecture

Expression profiling provides a powerful approach to define the underlying molecular mechanisms in disease. Several techniques referred collectively to as gene profiling may be also helpful in the analysis of the phenotype of mice with targeted mutations, especially if applied to distinct histological compartments, to specific cell types or to evaluate the effect of specific challenges, such as infection. Here we review several of the existing techniques applicable to genetic knockout studies, and share our experience from the study of mice with tumor necrosis factor (TNF) and lymphotoxin (LT) deficiencies, with specific emphasis on the distinction between TNF- and LT-mediated signalling pathways in vivo. Gene expression profiling analysis of TNF/LT-deficient mice supports the notion that TNF and LT, originally discovered as distinct biological activities, manifest both distinct and redundant functions in vivo.

Partial IgA-Deficiency with Increased Th2-Type Cytokines in TGF-β1 Knockout Mice

Though it has been shown that TGF-β1 directs B cells to switch to IgA in vitro, no studies have assessed TGF-β1 effects on mucosal vs systemic immunity in vivo. When the B cell functions of TGF-β1 gene-disrupted (TGF-β1−/−) mice were analyzed, significantly decreased IgA levels and increased IgG and IgM levels in serum and external secretions were observed. Further, analysis of Ab forming cells (AFC) isolated from both mucosal and systemic lymphoid tissue showed elevated IgM, IgG, and IgE, with decreased IgA AFC. A lack of IgA-committed B cells was seen in TGF-β1−/− mice, especially in the gastrointestinal (GI) tract. Splenic T cells triggered via the TCR expressed elevated Th2-type cytokines and, consistent with this observation, a 31-fold increase in serum IgE was seen in TGF-β1−/− mice. Thus, uncontrolled B cell responses, which include elevated IgE levels, a lack of antiinflammatory IgA, and an excess of complement-binding IgG and IgM Abs, will promote inflammation at mucosal surfaces in TGF-β1−/− mice and likely contribute to pulmonary and GI tract lesions, ultimately leading to the early death of these mice.

Imprints from the oropharyngeal mucosa: a novel method for studies of cell-kinetics and spatial relations between leukocytes, epithelial cells and bacteria in the secretion on the surface of the mucosa

Cell-kinetics and spatial relations between the cellular elements in the secretion on the mucosal surfaces of the oral cavity and the pharynx were studied with a new imprint technique whereby pieces of foam-plastic are pressed against the mucosal surfaces and then immediately against a glass slide. For visualisation of leukocytes, epithelial cells and bacteria, imprints were stained according to May Grünewald-Giemsa and with acridine orange. For visualisation and discrimination between T and B-cells, slides were stained with immunohistochemical technique using anti-CD-3 and anti-CD-19, respectively, as antibodies. Imprints were also prepared for scanning electron microscopy (SEM). The results show that there are large numbers of morphologically intact cells in the secretions and that there are statistically significant differences between the different mucosal areas as regards numbers, types and spatial relations between the cellular elements in the surface secretions. Rather great inter- and intra-individual differences in cellular composition were observed, indicating a dynamic system. This was further documented by observation of a dominance of polymorphonuclear leukocytes on the tonsillar surface, in contrast to the dominance of mononuclear leukocytes in secretion from the mesopharynx. We consider that this new imprint method is reliable and gives representative samples from the surface secretion. The results clearly show the need for further studies concerning the physiological role of the cellular elements in the surface secretion of the oral cavity and mesopharynx.

Changes in the structure of the cell surface carbohydrates of the chinchilla tubotympanum following Streptococcus pneumoniae-induced otitis media

Streptococcus pneumoniae (Spn) are among the most frequently isolated pathogens in acute otitis media (AOM) and in otitis media with effusion (OME). Recently, the specific receptor for Spn has been identified as the trisaccharide unit Gal beta 1-4 GlcNAc beta 1-3 Gal beta with GlcNAc beta 1-3 Gal beta as the principal binding site. During the colonization of mucosal surfaces, pneumococci produce a variety of enzymes. This study was conducted to identify any resulting changes in the cell surface carbohydrate structure due to the action of these enzymes during pneumococcal otitis media (OM) in chinchillas. Using a lectin histochemical method with seven different lectins (SNA, LFA, WGA, Succ WGA, BSL II, PNA, ECL), the labeling pattern revealed not only the removal of the terminal sialic acid, but also the exposure of N-acetyl-glucosamine. These results suggested that Spn-produced enzymes uncover part of their own receptor structure and thus may facilitate adherence and subsequent infection.

Relationship of immediate and delayed hypersensitivity to nasopharyngeal and intestinal growth of Candida albicans in allergic subjects

The growth of C. albicans yeast in the nasopharynx and in the anus as well as allergy symptoms were followed up for 8 months in 67 patients with bronchial asthma, allergic rhinitis and/or atopic eczema. 38 of the patients were skin prick test positive and 29 negative to C. albicans allergen extract. 32 of the patients had positive and 19 negative delayed skin reactions. The nasal, bronchial and skin symptoms of the yeast-sensitive allergic patients were not associated with the nasopharyngeal nor anal occurrence of C. albicans or other yeasts. The use of nasal or inhaled steroids had no effect on the occurrence of Candida in the nasopharynx. It was observed that immediate skin sensitivity had a positive correlation and the delayed sensitivity a negative correlation with the occurrence of C. albicans growth in nasopharynx and anus. These findings are in agreement with the concept that impaired cell-mediated immunity to C. albicans may lead to increased IgE response. This may explain the increased liability towards C. albicans nasopharyngeal and gastrointestinal "saprophytic" growth.

Host defense development in gut and related disorders

The gastrointestinal tract serves as an important interface between ingested elements from the external environment and the internal milieu of the person. Maturation of this intestinal barrier appears to occur along with the normal development of other organ systems. Evidence is presented for this maturational process, and the relation of this immature barrier to certain disease states seen in the neonatal period (e.g., infectious diarrhea, necrotizing enterocolitis, and allergic disease) is discussed.