Influences of long-term antibiotic administration on Peyer's patch lymphocytes and mucosal immunoglobulin A levels in a mouse model

The gene or not the gene--that is the question: understanding the genetically engineered mouse phenotype

Embryonic stem cells have had a significant impact on understanding gene function and gene interactions through the use of genetically engineered mice. However, the genetic context (ie, mouse strain) in which these modifications in alleles are made may have a considerable effect on the phenotypic changes identified in these mice. In addition, tissue- and time-specific gene expression systems may generate unanticipated outcomes. This article discusses the history of embryonic stem cells, reviews how mouse strain can affect phenotype (using specific examples), and examines some of the caveats of conditional gene expression systems.

Shifting the balance: antibiotic effects on host-microbiota mutualism

Antibiotics have been used effectively as a means to treat bacterial infections in humans and animals for over half a century. However, through their use, lasting alterations are being made to a mutualistic relationship that has taken millennia to evolve: the relationship between the host and its microbiota. Host-microbiota interactions are dynamic; therefore, changes in the microbiota as a consequence of antibiotic treatment can result in the dysregulation of host immune homeostasis and an increased susceptibility to disease. A better understanding of both the changes in the microbiota as a result of antibiotic treatment and the consequential changes in host immune homeostasis is imperative, so that these effects can be mitigated.

Triennial Growth Symposium: a review of science leading to host-targeted antibody strategies for preventing growth depression due to microbial colonization

In this review, the science used to develop host-targeted therapies for improving animal growth and feed efficiency is presented. In contrast to targeting the microbiota of the host, endogenous host proteins are targeted to regulate an overactive inflammatory response in the host. Activation of the immune/inflammatory systems of an animal is costly in terms of growth and feed efficiency. For example, reduced rates of BW gain and poorer feed efficiency in vaccinated animals compared with nonvaccinated animals have been well documented. Also, the growth rate and feed efficiency of animals colonized by microorganisms is only 80 to 90% of their germ-free counterparts. Further evidence of a cost associated with immune activation is that strategies that enhance the immune capability of an animal can reduce animal growth and feed efficiency. Research now indicates that the growth-promoting effects of antibiotics are indirect, and more likely the result of reduced immune activation due to decreased microbial exposure. Studies of mechanisms by which immune/inflammatory activation reduces animal growth and feed efficiency have shown that cytokines of the acute inflammatory response (i.e., IL-1 and tumor necrosis factor α) are key triggers for host muscle wasting. Cytokine-induced muscle wasting is linked to PG signaling pathways, and it has been proposed that regulation of the PG signaling pathways provide host targets for preventing an overreactive or unwarranted inflammatory event. Intestinal secretory phospholipase A(2) (sPLA(2)) has been found to be a useful and accessible (i.e., found in the intestinal lumen) host target for the regulation of an overreactive inflammatory response to conventional environments. This review presents the science and strategy for the regulation of intestinal sPLA(2) using orally administered egg yolk antibody against the enzyme. Clinically healthy animals fed egg antibodies to sPLA(2) had improved growth and feed efficiency. Literature presented indicates that use of host-targeted strategies for regulating the overexpression of inflammatory processes in an animal may provide new mechanisms to improve animal growth and feed efficiency.

Intestinal bacteria and the regulation of immune cell homeostasis

The human intestine is colonized by an estimated 100 trillion bacteria. Some of these bacteria are essential for normal physiology, whereas others have been implicated in the pathogenesis of multiple inflammatory diseases including IBD and asthma. This review examines the influence of signals from intestinal bacteria on the homeostasis of the mammalian immune system in the context of health and disease. We review the bacterial composition of the mammalian intestine, known bacterial-derived immunoregulatory molecules, and the mammalian innate immune receptors that recognize them. We discuss the influence of bacterial-derived signals on immune cell function and the mechanisms by which these signals modulate the development and progression of inflammatory disease. We conclude with an examination of successes and future challenges in using bacterial communities or their products in the prevention or treatment of human disease.