Intraepithelial lymphocytes from villus tip and crypt portions of the murine small intestine show distinct characteristics

HOPX+ injury-resistant intestinal stem cells drive epithelial recovery after severe intestinal ischemia

Intestinal ischemia is a life-threatening emergency with mortality rates of 50%-80% due to epithelial cell death and resultant barrier loss. Loss of the epithelial barrier occurs in conditions including intestinal volvulus and neonatal necrotizing enterocolitis. Survival depends on effective epithelial repair; crypt-based intestinal epithelial stem cells (ISCs) are the source of epithelial renewal in homeostasis and after injury. Two ISC populations have been described: 1) active ISC [aISC; highly proliferative; leucine-rich-repeat-containing G protein-coupled receptor 5 (LGR5⁺)-positive or sex-determining region Y-box 9 -antigen Ki67-positive (SOX9⁺Ki67⁺)] and 2) reserve ISC [rISC; less proliferative; homeodomain-only protein X positive (HOPX⁺)]. The contributions of these ISCs have been evaluated both in vivo and in vitro using a porcine model of mesenteric vascular occlusion to understand mechanisms that modulate ISC recovery responses following ischemic injury. In our previously published work, we observed that rISC conversion to an activated state was associated with decreased HOPX expression during in vitro recovery. In the present study, we wanted to evaluate the direct role of HOPX on cellular proliferation during recovery after injury. Our data demonstrated that during early in vivo recovery, injury-resistant HOPX⁺ cells maintain quiescence. Subsequent early regeneration within the intestinal crypt occurs around 2 days after injury, a period in which HOPX expression decreased. When HOPX was silenced in vitro, cellular proliferation of injured cells was promoted during recovery. This suggests that HOPX may serve a functional role in ISC-mediated regeneration after injury and could be a target to control ISC proliferation.NEW & NOTEWORTHY This paper supports that rISCs are resistant to ischemic injury and likely an important source of cellular renewal following near-complete epithelial loss. Furthermore, we have evidence that HOPX controls ISC activity state and may be a critical signaling pathway during ISC-mediated repair. Finally, we use multiple novel methods to evaluate ISCs in a translationally relevant large animal model of severe intestinal injury and provide evidence for the potential role of rISCs as therapeutic targets.

Exposure to fatty acids modulates interferon production by intraepithelial lymphocytes

Intraepithelial lymphocytes (IELs) play important roles in intestinal mucosal immunity. Although fatty acids are known to modulate the functions of immune effector cells, there has been no information about how fat exposure affects immunological function of IELs. In this study, we examined how fatty acids of various chain lengths modulate the production of interferon (IFN)-gamma by IELs stimulated with T-cell receptor (TCR) or interleukin (IL)-12/IL-18. IELs isolated from the small intestine of BALB/c mice were stimulated with plate-coated anti-CD3 monoclonal antibody (mAb) or IL-12/IL-18. They were coincubated in microtiter plates for 3 days with various concentrations of fatty acid micelles. We used arachidonic acid, linoleic acid, and oleic acid as long-chain fatty acids, and used octanoic acid as a medium-chain fatty acid. IFN-gamma in the supernatants were measured by ELISA, and the expression of IFN-gamma mRNA in IELs was determined by RT-PCR. Significant production of IFN-gamma from IELs was observed after anti-CD3 mAb stimulation. The combination of IL-12 and IL-18 induced significant levels of IFN-gamma production without TCR stimulation. Increased IFN-gamma mRNA was also observed after anti-CD3 or IL-12/IL-18 stimulation. Long-chain fatty acids dose-dependently inhibited the stimulated-IFN-gamma production at concentrations greater than 10 micro M, but the medium-chain fatty acid did not cause any significant changes in IFN-gamma production. IFN-gamma production from gammadelta IELs was very low compared with alphabeta IELs, however, both populations showed similar attenuating patterns when treated with long-chain fatty acids. There is a possibility that the exposure of IELs to intraluminal fatty acids significantly modifies the immune function of intestinal mucosa.

Effects of radiation damage on intestinal morphology

The current flow of papers on intestinal structure, radiation science, and intestinal radiation response is reflected in the contents of this review. Multiparameter findings and changes in compartments, cells, or subcellular structure all contribute to the overall profile of the response. The well-recognized changes in proliferation, vessels, and fibrogenesis are accompanied by alterations in other compartments, such as neuroendocrine or immune components of the intestinal wall. The responses at the molecular level, such as in levels of hormones, cytokines, or neurotransmitters, are of fundamental importance. The intestine responds to localized radiation, or to changes in other organs that influence its structure or function: some structural parameters respond differently to different radiation schedules. Apart from radiation conditions, factors affecting the outcome include the pathophysiology of the irradiated subject and accompanying treatment or intervention. More progress in understanding the overall responses is expected in the next few years.

The intestinal mucosa as a target for dietary polyunsaturated fatty acids

Several studies have reported beneficial effects of dietary polyunsaturated fatty acids (PUFA) on various aspects of both human and animal health, and particular reference has been made to their effects on systemic immune responses. Both immune stimulation and immune suppression have been reported, with the outcome dependent on the type of PUFA, the target cell, as well as the immune competence of the cells before exposure. The systemic and the mucosal immune systems are discrete entities, which have evolved specific approaches in the defense of the host. The latter comprises several interconnected tissues, which communicate with one another through the action of soluble mediators and the trafficking of cellular components. After the oral mucosa, the intestinal epithelium and its associated gut-associated lymphoid tissue are the primary targets of dietary components. Absorption of dietary PUFA and its incorporation into intestinal tissues has been well studied, but the consequences of these events in relation to local immune responses have received little attention. This article describes some of the immune mechanisms operating at this barrier and, where possible, pinpoints areas for which a modulatory role for PUFA has already been demonstrated. Although not an exhaustive treatise of the subject, it is hoped that this review will foster research into the specific interaction between dietary PUFA and cell populations comprising the intestinal barrier.

Human nasopharyngeal-associated lymphoreticular tissues. Functional analysis of subepithelial and intraepithelial B and T cells from adenoids and tonsils

Subepithelial and intraepithelial lymphocytes of human adenoids and tonsils were characterized and directly compared to determine the potential contribution of these tissues to mucosal and systemic immune responses. The distribution of T and B cell subsets, cytokine patterns, and antibody (Ab) isotype profiles were similar for adenoids and tonsils. Both tissues contained predominantly B cells ( approximately 65%), approximately 5% macrophages, and 30% CD3(+) T cells. The T cells were primarily of the CD4(+) subset ( approximately 80%). Tonsillar intraepithelial lymphocytes were also enriched in B cells. The analysis of dispersed cells revealed a higher frequency of cells secreting IgG than IgA and the predominant Ig subclass profiles were IgG1 > IgG3 and IgA1 > IgA2, respectively. In situ analysis also revealed higher numbers of IgG- than IgA-positive cells. These IgG-positive cells were present in the epithelium and in the subepithelial zones of both tonsils and adenoids. Mitogen-triggered T cells from tonsils and adenoids produced both Th1- and Th2-type cytokines, clearly exhibiting their pluripotentiality for support of cell-mediated and Ab responses. Interestingly, antigen-specific T cells produced interferon-gamma and lower levels of interleukin-5. These results suggest that adenoids and tonsils of the nasopharyngeal-associated lymphoreticular tissues represent a distinct component of the mucosal-associated lymphoreticular tissues with features of both systemic and mucosal compartments.

T-lymphocyte-epithelial-cell interactions: integrin alpha(E)(CD103)beta(7), LEEP-CAM and chemokines

The epithelia are the avascular layers of cells that cover the environment-exposed surfaces of the body. It appears that T cells localize to selected sites in or adjacent to epithelia via the selective expression of adhesion molecules and chemokine receptors on T cells. These bind to counter-receptors and to chemokines expressed by epithelial cells. Recently, there has been an advance in our understanding of the interaction of the alpha(Ebeta7) integrin with its epithelial cell ligand, E-cadherin. In addition, a new adhesion molecule has been identified on non-intestinal epithelial cells, termed lymphocyte-endothelial-epithelial-cell adhesion molecule (LEEP-CAM). Finally, there have been advances in our understanding of the role of skin- or gut-epithelia-derived chemokines in regulating activated T cell homing to these sites.

Interleukin 12 and innate molecules for enhanced mucosal immunity

Recent strategies for understanding the mechanisms underlying mucosal immune responses and subsequent development of mucosal vaccines for induction of targeted immunity now include cytokines and molecules of innate immunity. These studies have shown that cytokines influencing the development of T helper (Th) cells differentially affect the outcome of mucosal vs. systemic immune responses to mucosal vaccines. Serum antigen-specific antibody (Ab) responses were enhanced when either IL-6 or IL-12 was mucosally administered with a protein antigen, while only IL-12 induced antigen-specific mucosal IgA Ab responses. Mucosal IL-6 and IL-12 also affected the type of Th cell responses induced by CD4+ T cells from mice that received IL-12 secreted larger amounts of IFN-gamma and IL-6 when compared with mice nasally treated with IL-6. Discrepancies in the ability to enhance mucosal or systemic immune responses were also observed when human neutrophil peptide (HNP) defensins or lymphotactin were nasally coadministered with protein antigens. Only lymphotactin promoted mucosal secretory IgA (S-IgA) Ab responses while both lymphotactin and defensins enhanced systemic immunity to mucosally co-administered protein antigens. Mixed antigen-specific Th1 -and Th2-type CD4+ T cell responses were induced in the systemic compartment by both lymphotactin and the mixture of HNP-1, HNP-2, and HNP-3 defensins. However, HNPs failed to significantly enhance cytokine secretion by mucosally derived, antigen-specific CD4+ T cells relative to those isolated from the systemic compartment. In summary, these studies clearly show that IL-12 and lymphotactin are able to trigger S-IgA Ab responses and provide new avenues for the design of safe and targeted mucosal vaccines.