Novel cellular interactions and networks involving the intestinal immune system and its microenvironment

Microbial-Driven Immunological Memory and Its Potential Role in Microbiome Editing for the Prevention of Colorectal Cancer

Over the last several years, many advances have been made in understanding the role of bacteria in the pathogenesis of gastrointestinal cancers. Beginning with Helicobacter pylori being recognized as the first bacterial carcinogen and the causative agent of most gastric cancers, more recent studies have examined the role of enteric microbes in colorectal cancer. In the digestive tract, these communities are numerous and have a complex interrelationship with local immune/inflammatory responses that impact the health of the host. As modifying the microbiome in the stomach has decreased the risk of gastric cancer, modifying the distal microbiome may decrease the risk of colorectal cancers. To date, very few studies have considered the notion that mucosal lymphocyte-dependent immune memory may confound attempts to change the microbial components in these communities. The goal of this review is to consider some of the factors impacting host-microbial interactions that affect colorectal cancer and raise questions about how immune memory responses to the local microbial consortium affect any attempt to modify the composition of the intestinal microbiome.

Quantitation of virus-specific classes of antibodies following immunization of mice with attenuated equine herpesvirus 1 and viral glycoprotein D

The antibody responses of CBA/J mice infected intranasally (i.n.) with either the attenuated KyA strain or the pathogenic RacL11 strain of equine herpesvirus 1 (EHV-1) or immunized with recombinant glycoprotein D (rgD) were investigated using the ELISPOT assay to measure EHV-1-specific antibody-secreting cells (ASC) in the regional lymphoid tissue of the respiratory tract. IgG, IgA, and IgM ASC specific for EHV-1 were detected in the mediastinal lymph nodes (MLN) and lungs 2 weeks after i.n. infection with EHV-1 strain KyA or RacL11, or immunization with heat-killed KyA or rgD. EHV-1-specific ASC were present in the MLN and lungs at 4 and 8 weeks, but declined in frequency by fivefold in the lung at 8 weeks. However, i.n. immunized (2 x 10(6) pfu KyA or 50 microgram rgD/mouse) mice infected at 8 weeks with pathogenic EHV-1 RacL11 resisted challenge and showed eight- and tenfold increases in MLN ASC and lung ASC, respectively, by 3 days after challenge. In contrast to the intranasal route of immunization, intraperitoneal immunization yielded ASC frequencies in the MLN and lungs that were only slightly above those of nonimmunized control mice. These data indicate that immunization with infectious or heat-killed EHV-1 KyA, or rgD, induces significant levels of virus-specific ASC both in the MLN and lungs, a specific memory B-cell response, and long-term protective immunity. The finding that the numbers of ASC induced by the pathogenic strain versus the attenuated strain of EHV-1, which were virtually identical, indicated that the ability to generate a B-cell response is independent of and does not contribute to EHV-1 virulence.

Generation of humoral immune responses against herpes simplex virus type 2 in the murine female genital tract

A murine model of genital infection with a thymidine kinase-deficient (tk-) strain of herpes simplex virus type 2 (HSV-2) was utilized to examine the local urogenital antibody response to HSV-2. Vaginal inoculation with HSV-2 tk- protected against a subsequent genital challenge with a lethal dose of virulent HSV-2. After primary vaginal infection, predominantly HSV-specific IgG antibodies were detected in serum and vaginal secretions. HSV-specific IgG antibody-secreting cells (ASC) were detected first and in greatest numbers in the genital lymph nodes (gLN) after primary HSV-2 tk- inoculation. HSV-specific IgG or IgA ASC were not detected in the urogenital mucosa after primary HSV-2 vaginal infection. Vaginal HSV-2 challenge of HSV-immune mice resulted in increased HSV-specific serum IgG antibody and vaginal IgA antibody titers. HSV-specific IgG ASC were detected by 4 days postchallenge in gLN and by Days 6 and 7 postchallenge in the spleen and genital mucosa. These results suggest that urogenital humoral responses originate in the gLN following HSV genital infection and that gLN may serve as the primary source of the HSV-specific IgG- and IgA-secreting cells present in the urogenital mucosa after vaginal challenge.

The role of the local immune response in the pathogenesis of peptic ulcer formation

Mucosal immune responses are designed to provide local protection against infection, without inducing excessive amounts of inflammation that would alter epithelial integrity or function. It has become clear that the epithelium not only serves as a barrier to exclude pathogens, but also initiates host responses to infection. Gastric epithelial cells infected with Helicobacter pylori can respond within hours to produce inflammatory mediators that recruit and activate neutrophils. The gastric epithelium can also be recognized by local T-cells, resulting in their activation and ability to induce epithelial damage. During infection with H. pylori, there is a remarkable increase in the level of local IgG antibodies, which may also recognize and damage the epithelium. Thus, activated neutrophils, T-cells and auto-antibodies may contribute to a weakened epithelial barrier that allows luminal acid and other factors to contribute to peptic ulceration. The epithelium appears to play a key role in the initiation of the local inflammatory and immune responses that may contribute to the more serious sequelae associated with H. pylori infection.

Interactions of mast cells with the nervous system ?Recent advances

This article reviews recent advances in the understanding of mast cell-nervous system interactions. It is drawn largely from work published within the last ten years, and discusses the anatomical and biochemical evidence of a functional connection between mast cells and the nervous system, and the implications that such a relationship may have for normal and abnormal physiological functioning. Mast cells are found at varying levels of association with the nervous system; in CNS parenchyma (mainly thalamus), in connective tissue coverings (e.g. meninges, endoneurium), and in close apposition to peripheral nerve endings in a variety of tissues. There is, as yet, no clearly defined role for mast cells in nervous system function, or vice-versa, and it seems most likely that their interactions fulfil mutually modulatory roles. By extension, pathological situations where one of the partners in this relationship is overly stimulated may lead to a dysregulation of the other, and contribute to disease symptomatology.

Interactions between Helicobacter pylori and the local mucosal immune system

The recognition that Helicobacter pylori is associated with an array of gastric disorders immediately raises several issues with regard to the role of the local immune system. The belief that the harsh gastric environment limits or prevents infection has perhaps dismissed studies into the immunology of the stomach as a low priority. Now, in combination with our understanding of local immune reactivity in pernicious anaemia, an interest in defining the contribution of the immune response in the pathogenesis of disease associated with H. pylori has fueled a great deal of interest. Furthermore, the evidence of local immunity to this bacteria has kindled interest that gastric immune/inflammatory responses may contribute to the treatment or prevention of a gastric infection.