Intraepithelial Lymphocytes Subpopulations Research Articles

Natural intraepithelial lymphocyte populations rise during necrotic enteritis in chickens.

Intraepithelial lymphocytes (IEL) reside in the epithelium at the interface between the contents of the intestinal lumen and the sterile environment of the lamina propria. Because of this strategic location, IEL play a crucial role in various immunological processes, ranging from pathogen control to tissue stability. In mice and humans, IEL exhibit high diversity, categorized into induced IEL (conventional CD4 and CD8αβ T cells) and natural IEL (TCRαβCD8αα, TCRγδ, and TCRneg IEL). In chickens, however, the subpopulations of IEL and their functions in enteric diseases remain unclear. Thus, we conducted this study to investigate the role of IEL populations during necrotic enteritis (NE) in chickens. At 14 days of age, sixty-three Specific-pathogen-free (SPF) birds were randomly assigned to three treatments: Control (sham challenge), Eimeria maxima challenge (EM), and Eimeria maxima + Clostridium Perfringens (C. Perfringens) co-challenge (EM/CP). The EM and EM/CP birds were infected with Eimeria maxima at day 14 of age, and EM/CP birds were additionally orally inoculated with C. perfringens at days 18 and 19 of age. Birds were weighed at days 18, 20, and 26 of age to assess body weight gain (BWG). At 20 days of age (1 day-post C. perfringens infection; dpi), and 26 days of age (7 dpi), 7 birds per treatment were euthanized, and jejunum was harvested for gross lesion scores, IEL isolation, and gene expression. The EM/CP birds exhibited subclinical NE disease, lower BWG and shorter colon length. The Most changes in the IEL populations were observed at 1 dpi. The EM/CP group showed substantial increases in the total number of natural IEL subsets, including TCRαβ+CD4-CD8-, TCRαβ+CD8αα+, TCRγδ+, TCRneg and innate CD8α (iCD8α) cells by at least two-fold. However, by 7 dpi, only the number of TCRαβ+CD4-CD8- and TCRαβ+CD8αα+ IEL maintained their increase in the EM/CP group. The EM/CP group had significantly higher expression of proinflammatory cytokines (IL-1β and IFN-γ) and Osteopontin (OPN) in the jejunum at 1 dpi. These findings suggest that natural IEL with innate and innate-like functions might play a critical role in the host response during subclinical NE, potentially conferring protection against C. perfringens infection.

Unconventional Intestinal Intraepithelial Lymphocytes in Health and Disease.

The intestinal epithelium is constantly exposed to a myriad of antigenic stimuli derived from commensals, food particles and pathogens present in the lumen of the intestines. This complex environment requires a similarly complex immune system capable of preventing exacerbated responses against food particles and commensals, while at the same time eliminating potential pathogens. These functions are accomplished in part by the intraepithelial lymphocyte (IEL) compartment. IELs are a diverse group of immune cells that primarily reside in between intestinal epithelial cells, maintaining an intimate association with these cells. IELs are a diverse population of cells: some of them express a T cell receptor (TCR), while others do not, and within TCR+ and TCR- IELs there are many IEL subpopulations that represent different developmental pathways and functions. In this review, we will focus on "unconventional" T cells present in the intestinal epithelium, in particular TCRγδ+, TCRαβ+CD4+CD8αα+, and TCRαβ+CD8αα+ IELs. We will discuss their development and potential functions both in humans and in mice.

Osteopontin and iCD8α Cells Promote Intestinal Intraepithelial Lymphocyte Homeostasis.

Intestinal intraepithelial lymphocytes (IEL) comprise a diverse population of cells residing in the epithelium at the interface between the intestinal lumen and the sterile environment of the lamina propria. Because of this anatomical location, IEL are considered critical components of intestinal immune responses. Indeed, IEL are involved in many different immunological processes, ranging from pathogen control to tissue stability. However, despite their critical importance in mucosal immune responses, very little is known about the homeostasis of different IEL subpopulations. The phosphoprotein osteopontin is important for critical physiological processes, including cellular immune responses, such as survival of Th17 cells and homeostasis of NK cells among others. Because of its impact in the immune system, we investigated the role of osteopontin in the homeostasis of IEL. In this study, we report that mice deficient in the expression of osteopontin exhibit reduced numbers of the IEL subpopulations TCRγδ+, TCRβ+CD4+, TCRβ+CD4+CD8α+, and TCRβ+CD8αα+ cells in comparison with wild-type mice. For some IEL subpopulations, the decrease in cell numbers could be attributed to apoptosis and reduced cell division. Moreover, we show in vitro that exogenous osteopontin stimulates the survival of murine IEL subpopulations and unfractionated IEL derived from human intestines, an effect mediated by CD44, a known osteopontin receptor. We also show that iCD8α IEL but not TCRγδ+ IEL, TCRβ+ IEL, or intestinal epithelial cells, can promote survival of different IEL populations via osteopontin, indicating an important role for iCD8α cells in the homeostasis of IEL.

MicroRNA-150 controls differentiation of intraepithelial lymphocytes through TGF-β receptor II regulation

Intraepithelial lymphocytes (IELs) in the intestines play pivotal roles in maintaining the integrity of the mucosa, regulating immune cells, and protecting against pathogenic invasion. Although several extrinsic factors, such as TGF-β, have been identified to contribute to IEL generation, intrinsic regulatory factors have not been determined fully. Here we investigated the regulation of IEL differentiation and the underlying mechanisms in mice. We analyzed IELs and the expression of molecules associated with IEL differentiation in wild-type control and microRNA (miRNA)-150 knockout mice. Methotrexate was administered to mice lacking miR-150 and control mice. miR-150 deficiency reduced the IEL population in the small intestine and increased susceptibility to methotrexate-induced mucositis. Evaluation of expression of IEL differentiation-associated molecules showed that miR-150-deficient IELs exhibited decreased expression of TGF-β receptor (TGF-βR) II, CD103, CD8αα, and Runt-related transcription factor 3 in all the IEL subpopulations. The reduced expression of TGF-βRII in miR-150-deficient IELs was caused by increased expression of c-Myb/miR-20a. Restoration of miR-150 or inhibition of miR-20a recovered the TGF-βRII expression. miR-150 is an intrinsic regulator of IEL differentiation through TGF-βRII regulation. miR-150-mediated IEL generation is crucial for maintaining intestinal integrity against anticancer drug-induced mucositis.

Aryl Hydrocarbon Receptor Activation Down-Regulates IL-7 and Reduces Inflammation in a Mouse Model of DSS-Induced Colitis.

The pathogenesis of inflammatory bowel disease (IBD) is associated with dysregulation of intestinal immune system. Aryl hydrocarbon receptor (AHR) is believed to control the chronic inflammation in the gut. Besides, interleukin-7 (IL-7) is proved to be an important cytokine that activates mucosal inflammation in IBD. Moreover, intraepithelial lymphocytes (IELs) are one of the key immunological compartments involved in regulating intestinal inflammation. In this study, we investigated the function of 6-formylindolo (3,2-b) carbazole (Ficz), a ligand of AHR, on IL-7, colitis, and IEL phenotypes. Colitis was induced by administration of dextran sulfate sodium (DSS) to wild-type C57BL/6J mice for 7 days. Mice were weighted, colon tissues were collected and measured, and histology analyses were performed. IELs were isolated from colon, and the phenotype and activation of IELs were examined using flow cytometry detection. The expression of AHR and IL-7 was measured by immunofluorescence, Western blot, and RT-PCR. Ficz down-regulated epithelial-derived IL-7 expression in mice with DSS-induced colitis and ameliorated DSS-induced colitis. Ficz also decreased CD8αβ(+) and CD8(+) IEL subpopulations, enhanced TCRγδ(+) IEL subpopulation, and reduced the percentage of activated CD4(+) and CD8(+) subpopulations. Ficz could down-regulate epithelial-derived IL-7 expression in mice with DSS-induced colitis and inhibit inflammation in the gastrointestinal tract of mice. AHR-related compounds might be the new and promising therapeutic medicaments for the treatment of patients with IBD.

Phenotypic characterization of canine intestinal intraepithelial lymphocytes in dogs with inflammatory bowel disease.

BackgroundMany dogs suffering from inflammatory bowel disease (IBD) are presented to veterinary clinics. These patients are diagnosed based on a history of chronic gastrointestinal signs and biopsy‐confirmed histopathologic intestinal inflammation. Intestinal intraepithelial lymphocytes (IEL) are part of the first line of defense in the gastrointestinal immune system. Alterations in IEL subsets may play a role in the pathogenesis of IBD.HypothesisThe aim of this study was to characterize the phenotypes of IEL in dogs with IBD compared with healthy control dogs.AnimalsIntestinal intraepithelial lymphocytes subpopulations of control dogs (n = 5) obtained from endoscopic biopsies (EB) were compared to those obtained from full thickness biopsies (FTB) on the same day. In addition, the phenotypes of IEL from FTB of control dogs (n = 10) were compared with EB of IBD dogs (n = 10). Each participant was scored clinically using the canine inflammatory bowel disease activity index (CIBDAI), and all samples were graded histopathologically. Three‐color flow cytometry of isolated IEL was performed using monoclonal antibodies against T‐ and B‐lymphocyte subpopulations.ResultsNo significant differences in the composition of IEL subpopulations were found in control dogs based on method of biopsy. The IBD dogs had significantly higher CIBDAI and histopathologic scores compared with control dogs and their IEL contained a significantly higher frequency TCRγδ T‐cells.Conclusions and Clinical ImportanceEndoscopic biopsies provide suitable samples for 3‐color flow cytometry when studying canine intestinal IEL and IBD patients show significant changes of major T‐cell subsets compared to healthy control dogs.

Disturbance of intraepithelial lymphocytes in a murine model of acute intestinal ischemia/reperfusion

Strategically located at the epithelial basolateral surface, intraepithelial lymphocytes (IELs) are intimately associated with epithelial cells and maintain the epithelial barrier integrity. Intestinal ischemia-reperfusion (I/R)-induced acute injury not only damages the epithelium but also affects the mucosal barrier function. Therefore, we hypothesized that I/R-induced mucosal damage would affect IEL phenotype and function. Adult C57BL/6J mice were treated with intestinal I/R or sham. Mice were euthanized at 6 h after I/R, and the small bowel was harvested for histological examination and to calculate the transmembrane resistance. Occludin expression and IEL location were detected through immunohistochemistry. The IEL phenotype, activation, and apoptosis were examined using flow cytometry. Cytokine and anti-apoptosis-associated gene expressions were measured through RT-PCR. Intestinal I/R induced the destruction of epithelial cells and intercellular molecules (occludin), resulting in IEL detachment from the epithelium. I/R also significantly increased the CD8αβ, CD4, and TCRαβ IEL subpopulations and significantly changed IEL-derived cytokine expression. Furthermore, I/R enhanced activation and promoted apoptosis in IELs. I/R-induced acute intestinal mucosal damage significantly affected IEL phenotype and function. These findings provide profound insight into potential IEL-mediated epithelial barrier dysfunction after intestinal I/R.

High Proportion of Granzyme B+ Intraepithelial Lymphocytes Contributes to Epithelial Apoptosis in Helicobacter pylori‐Associated Lymphocytic Gastritis

Helicobacter pylori infection has been linked to the development of lymphocytic gastritis (LG) characterized by ≥25 intraepithelial lymphocytes (IELs) per 100 epithelial cells. We hypothesize that the changes in the subpopulation and/or cytotoxicity of IELs leading to epithelial cell apoptosis may be involved in the pathogenesis of H.pylori-associated LG. We examined IEL subpopulations and the expression of cytotoxic molecules by IELs in biopsy specimens from 36 patients with H.pylori-associated LG by immunostainings for CD3, CD4, CD8, T-cell-restricted intracellular antigen-1 (TIA-1), and granzyme B (GrB) and compared the results with those obtained from 49 patients with H.pylori-associated gastritis (HPG). To investigate whether the IEL-mediated cytotoxicity is related to the increase of epithelial apoptosis, we performed a terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay using ApopTag detection kit. Between LG and HPG groups, significant differences in the number of CD3+, CD4+, CD8+, TIA-1+ or GrB+ IELs, and ApopTag indices were found. Among the CD3+ IELs, the proportion of CD8+ IELs or TIA-1+ IELs did not differ between two groups. The LG group showed a selective increase in GrB-positive, phenotypically activated IELs, which was paralleled by an increase in ApopTag indices. In contrast, the HPG group showed more heterogeneous IEL subpopulations with more CD4+ IELs and less GrB+ IELs compared with the LG group, and we did not find any significant variable contributing to the epithelial apoptosis in the HPG group. This study shows that in addition to the numerical increase in the IELs, there are significant changes in the subpopulations and cytotoxicity of IELs between HPG and H.pylori-associated LG. In particular, enhanced GrB-associated cytotoxicity of the IELs in H.pylori-associated LG contributes to an increase in epithelial apoptosis.

Lymphocyte subpopulations in blood and duodenal epithelium of broilers fed diets contaminated with deoxynivalenol and zearalenone

The effects of two dietary levels of Fusarium mycotoxins deoxynivalenol (DON) and zearalenone (ZEA) on subpopulations of peripheral blood and duodenal intraepithelial lymphocytes in Ross 308 hybrid broiler chickens of both sexes were examined. From the day of hatching to the age of two weeks three groups of chickens were fed the same uncontaminated control diet. After 14 days, broilers in two of the groups were switched to otherwise identical experimental diets containing DON and ZEA. The diet of Group 2 contained DON and ZEA, each at a level of 3.4 mg/kg and the Group 3 diet contained DON and ZEA at 8.2 and 8.3 mg/kg, respectively. Contaminated diets were prepared in the laboratory using maize cultivated with Fusarium graminearum. Group 1 (control) continued with intake of uncontaminated diet for entire experiment. At the age of four weeks samples of blood and duodenal tissue were collected. Intake of both contaminated diets reduced blood phagocytic activity (P<0.001) whereas numbers of various types of peripheral white blood cells were not affected. Among different blood lymphocyte populations investigated, only the counts of CD3 + cells were lowered by diet with higher mycotoxin levels (P=0.021). In duodenal epithelium, the large increase in cells expressing MHC II was observed due to intake of both diets contaminated with lower and higher mycotoxins contents (P<0.001) while the IgA + cell subpopulation was decreased (P=0.018). The other intraepithelial lymphocyte subpopulations in duodenum examined (CD3 +, CD4 +, CD8 + and CD44 +) were not influenced by intake of contaminated diets (P>0.05). Results suggest that intake of diets contaminated with DON and ZEA at medium levels may affect some blood and intraepithelial duodenal lymphocyte subpopulations and compromise blood phagocytic activity in broilers.

Effects of direct-fed microbials on growth performance, gut morphometry, and immune characteristics in broiler chickens

This study was conducted to compare growth performance, gut morphometry, and parameters of local and systemic immunity in broiler chickens fed for 22 consecutive days with a diet supplemented with Bacillus spp. as direct-fed microbials (DFM), a commercial product incorporating 3 DFM, or a nonsupplemented diet. Direct-fed microbials did not significantly modify BW gain and most failed to affect serum antibody levels in response to immunization with a recombinant Eimeria protein. However, altered intestinal morphometric measurements were readily apparent in DFM-fed chickens as revealed by increased villus height and crypt depth compared with non-DFM-fed controls. In addition, serum levels of alpha-1-acid glycoprotein as an inflammatory marker were reduced in DFM-fed birds, whereas splenic lymphocyte proliferation, intestine intraepithelial lymphocyte subpopulations, and cytokine mRNA levels in intraepithelial lymphocytes were increased, decreased, or unchanged compared with controls depending on the DFM used. These results provide a rational scientific basis for future studies to investigate DFM as immunomodulating agents to enhance host protective immunity against enteric pathogens in broiler chickens.

Prevention of TNBS-induced colitis by different Lactobacillus and Bifidobacterium strains is associated with an expansion of γδT and regulatory T cells of intestinal intraepithelial lymphocytes

Probiotics may protect against inflammatory bowel disease through regulation of lamina propria lymphocytes (LPLs) function. Data are lacking on possible involvement of intraepithelial lymphocytes (IELs). The aim of this study was to investigate whether different probiotic mixtures prevented gut inflammatory disease and the role of both IELs and LPLs. BALB/c mice received 2 probiotic mixtures orally for 3 weeks, as Mix1 (Lactobacillus acidophilus and Bifidobacterium longum), or Mix2 (Lactobacillus plantarum, Streptococcus thermophilus, and Bifidobacterium animalis subsp. lactis). Colitis was induced by intrarectal administration of trinitrobenzene sulfonic acid (TNBS). Probiotics in stools were analyzed by real-time polymerase chain reaction (PCR). Colon subpopulations of IELs and LPLs were assayed by flow cytometry. Serum cytokines were measured by cytometric bead array (CBA). All probiotics colonized the intestine. The 2 mixtures prevented the TNBS-induced intestinal damage, and Mix1 was the most effective. The Mix1 protection was associated with a reduction in CD4(+) cells of IELs and LPLs, an increase in gammadeltaT cells of IELs, and a decrease in gammadeltaT cells of LPLs. An expansion of T regulatory (Treg) cells of IELs was induced by Mix1 and Mix2. Both probiotic mixtures inhibited tumor necrosis factor (TNF)-alpha and monocyte chemotactic protein (MCP)-1 production and upregulated interleukin (IL)-10. In addition, Mix1 prevented the TNBS-induced increase of IL-12 and interferon (IFN)-gamma. The 2 probiotic mixtures were able to prevent the TNBS-induced colitis; the L. acidophilus and B. longum mixture was the most effective. Other than an involvement of LPLs, our results report a novel importance of the IELs population in probiotic protection.

Antimicrobial activity of Enterococcus faecium EF 55 against Salmonella Enteritidis in chicks

The protective effect of Enterococcus faecium EF 55 against Salmonella enterica serovar Enteritidis phage type 4 (SE PT4) was studied in 1-day-old chicks. The EF 55 strain (isolated and characterised by the authors earlier) was applied daily (1.10(9) CFU/0.2 ml PBS) for 7 days. Oral inoculation of the SE PT4 strain was performed on day 8 in a single dose of 5.10(8) CFU/0.2 ml PBS. The experiment lasted for 21 days. Samples were collected on day 1 of the experiment to verify the absence of Salmonella, on day 8 to check colonisation of EF 55 and immunological status in experimental birds, and on days 2, 4, 6, 8 and 14 after SE PT4 infection of chicks. Strain EF 55 sufficiently colonised the digestive tract of chicks after 7 days of application. The highest numbers of EF 55 in the faeces of chicks were observed before SE infection and persisted to day 6 post infection (p.i.) in both the EF and EF+SE groups. PCR confirmed the identity of the EF 55 strain. The counts of SE PT4 strain in faeces of the EF+SE group were significantly reduced in comparison to those in the SE group on days 2 and 14 p.i. (P < 0.01). The significant reduction of salmonellae in the caecum was recorded at the end of the experiment (day 14 p.i.) in the EF+SE group in comparison to the SE group (P < 0.01). At day 4 p.i., colonies of S. Enteritidis PT4 were found in the liver of chicks of the SE group in a higher concentration than in chicks of the EF+SE group (P < 0.001). Salmonellae were isolated from the liver until days 8 and 6 p.i. in the SE and EF+SE groups, respectively. The mean values of actual lymphocyte subpopulations in the blood and the relative percentage of caecal intraepithelial lymphocyte subpopulations (CD4, CD8, CD44, TCR, MHC II and IgM) were not influenced at a statistically significant level by the application of the EF 55 and/or the SE PT4 strain. The results demonstrate the antimicrobial effect of E. faecium EF 55 against S. Enteritidis PT4.

Changes in Lymphocyte Phenotypes and Cytokine Production by Surgical Stress in a Rat Small Intestinal Resection Model

Small intestinal resection rats are used widely as a malabsorption model, but the immunological changes are unclear. We examined the changes in systemic and mucosal immune status after a small intestinal resection in rats with a controlled nutritional status. Rats had 60% of their small intestine removed. At 5 days after the surgery, spleen cells and intraepithelial lymphocytes (IEL) were isolated. The phenotypes of spleen cells and IEL, the production patterns of Th1 and Th2 cytokines, and the proinflammatory cytokine levels in the plasma were measured. CD4+ T cells in the blood and spleen were significantly decreased in the Resection group (p<0.05). In contrast, IEL subpopulations were not different between the two groups. Interferon-γ production from the spleen cells was significantly decreased in the Resection group (p<0.05). Interleukin (IL)-4 production was not different between the two groups. Plasma IL-6 concentrations were significantly elevated in the Resection group 6 h after surgery (p<0.05). In conclusions, small intestinal resection in rats suppressed systemic immunity, and this model is useful as a surgical stress model.

Enterocyte apoptosis and TPN-associated intestinal mucosal atrophy: a view of the chicken or the egg?

Enterocyte apoptosis and TPN-associated intestinal mucosal atrophy: a view of the chicken or the egg?

Alteration of intestinal intraepithelial lymphocytes after massive small bowel resection

Background. Intraepithelial lymphocytes (IEL) comprise the inner most layer of the gut immune system, and play a critical role in protecting the host from enteric organisms. Massive small bowel resection (MSBR) is one such clinical condition where patients are at particularly high risk for the development of such enteric infectious complications. Because of this, we hypothesized that the IEL may change significantly after the formation of a MSBR. To address this, a mouse model of MSBR was created and the acute phenotypic and functional characteristics of the IEL were studied. Materials and methods. Mice underwent a 70% mid-small bowel resection. After 7 days, IEL were isolated and analyzed for phenotypic changes by flow cytometry. IEL cytokine expression was performed with semiquantitative polymerase chain reaction techniques. To assess the functional significance of these changes, IEL proliferative response was assessed in vitro. Results. MSBR led to significant decreases in specific IEL subpopulations: CD 44+ (used as a marker of cell maturity); CD 8αβ+ (marker of thymic derivation), and CD 69+ (marker of T cell activation). Compared with controls, IEL TNF-α mRNA expression increased 84%, while IL-2 and IL-10 mRNA expression decreased by 69 and 72%, respectively. Spontaneous proliferation of IEL in the MSBR group was significantly higher than controls, however, proliferation failed to increase with T cell stimulation. Conclusion. These changes suggest a shift to a more immature and possibly less activated cell population. It is possible that such alterations may play an important role in the increase in enterically derived infections in patients with MSBR.

Lymphocyte subpopulations in hypertrophied adenoid in children

Adenoid hypertophy is a common feature of childhood. It is currently accepted that it is caused by the antigen-stimulated increased activity of lymphocyte B (D. Bani, O. Gallo, O. Fini-Storchi, Intraepithelial lymphocyte subpopulations and dendritic accessory cells in normal and hypertrophic adenoids, Laryngoscope 10 (1994) 869–873). The adenoid decreases its size with age but the accompanying function alterations are not fully understood (L. Zawadzka-Glos, M. Chmielik, M. Wasik, Cell mediated response in hypertrophied tonsils in children, Nowa Pediatr. 4 (1997) 12–13). The understanding of the adenoid structure that undergoes some changes during the growth period is essential for evaluation of indications for adnoidectomy and assessment of its potential results. The aim of this study was to evaluate lymphocyte subpopulations in adenoid according to age. The analysed material was adenoids removed on the grounds of hypertrophy, which caused obstructive symptoms and/or otitis media with effusion onset. In the present study, we did not find any statistically significant differences among lymphocytes B, Th, and Ts subpopulations, respectively, in the adenoids of any of the age groups. We have found a statistically significant CD3 + HLA-DR + cell percentage decrease in the group of children from 5 to 10 and above 10 years of age, respectively. We have also found a statistically significant increase in the percentage of NK (CD3 − CD16 + 56 +) lymphocytes in relation to age. On the grounds of the current study, it may be stated that some changes in lymphocyte subpopulations in the adenoid take place with age.

Mucosal immune network in the gut for the control of infectious diseases.

The common mucosal immune system (CMIS) consists of an integrated cross-communication pathway of lymphoid tissues made up of inductive and effector sites for host protection against pathogenic microorganisms. Major effector molecules of the CMIS include IgA antibodies and cytokines, chemokines and their corresponding receptors. Secretory IgA (S-IgA), the major immunoglobulin, is induced by gut-associated lymphoreticular tissue (GALT)-derived B cells with the help of Th1- and Th2-type CD4(+) T lymphocytes. Cytotoxic T lymphocytes (CTLs) in the mucosal epithelium, a subpopulation of intraepithelial lymphocytes (IELs), also help maintain the mucosal barrier. The CMIS is unique in that it can provide both positive and negative signals for the induction and regulation of immune responses in both the mucosal and systemic compartments after oral or nasal antigen exposure. Prevention of infection through mucosal surfaces can be achieved by the CMIS through connections between inductive (e.g. GALT) and effector tissues. When vaccine antigens are enterically administered together with mucosal adjuvants [e.g. cholera toxin (CT), heat-labile toxin produced by Escherichia coli (LT) and IL-12], antigen-specific Th1/Th2 and IgA B cell responses are induced simultaneously in the mucosal effector compartment. Since these antigen-specific immune responses are not generated by oral vaccine without mucosal adjuvant, safe and effective adjuvants for the induction of antigen-specific S-IgA and CTL responses are essential for the development of mucosal vaccines for protection against infectious diseases. Finally, recent findings suggest the presence of a CMIS-independent IgA induction pathway, which also must be considered in the development of mucosal vaccines.

Prolactin and prolactin receptor expression in rat, small intestine, intraepithelial lymphocytes during neonatal development.

Intraepithelial lymphocytes (IEL) are specialized T cells found between the epithelial cells of the small intestine. Because of their location, IEL are the first lymphocytes to contact intestinal bacteria and food antigens. In the neonate, IEL may be the first cells of the immune system to interact with milk-borne hormones including prolactin (PRL). PRL, an endocrine hormone abundant in breast milk, interacts with cells through surface receptors. PRL has been shown to function as an immunoregulator and may affect the development of the newborn's immune system. To determine if PRL plays a role in IEL development, small intestine IEL from rats of various ages were examined for the presence of surface prolactin receptor (PRL-R) and several lymphoid markers by flow cytometry. Between birth and 96 days of age about 80% of IEL were found to express PRL-R. These same cells also expressed the mRNA for PRL. Additionally, all of the IEL subpopulations examined were found to express PRL-R. Analysis of the normal development of rat IEL revealed an age related increase in total IEL, CD4 positive cells as well as a peak in interleukin-2 receptor (IL-2R) expression at weaning. In summary, the results indicate that IEL express PRL and PRL-R. In addition, an activation marker, IL-2R, changes in expression during neonatal development.

Lymphocyte subsets in porcine tonsillar crypt epithelium

The palatine tonsils are part of the mucosa-associated lymphoid tissue (MALT), strategically located in the oropharynx at the entrance of respiratory and gastrointestinal tracts, and are recognized portals of entry and sites of multiplication and persistence of several pathogens in pigs. As the tonsillar crypt epithelium is in close contact with external environment and the underlying lymphoid tissue, the characterization of the intra-epithelial lymphocyte subpopulations is essential for the understanding of initial steps of pathogenesis of several diseases. In this work we investigated specific lymphocyte subsets in the tonsillar crypt epithelium of 10 adult healthy pigs, using monoclonal antibodies against lymphocyte markers CD3, CD4, CD8, γδ T cell receptor and immunoglobulin light-chain in an avidin–biotin immunoperoxidase technique. The crypt epithelium was usually extensively infiltrated by a diverse population of T cells and by B cells. The degree of infiltration of each subset was variable among animals and within individual animals. In the T cell population CD4 cells and γδ TCR cells predominated over CD8 cells. These data suggest that the crypt lymphoepithelium is capable of participating in both cellular and humoral immune responses and that γδ T cells may play an important role in the defense of this mucosa.

Altered development of intestinal intraepithelial lymphocytes in P-glycoprotein-deficient mice

Intraepithelial lymphocytes (IEL) that reside in the intestinal epithelium are known to exhibit phenotypic and functional characteristics that are distinct from other T cells. We have recently shown that peripheral T cells exclusively express an isoform of P-glycoprotein ( P-gp) encoded by the mdr1 a gene, but do not require mdr1 a expression for normal proliferative, cytokine, or cytotoxic responses. In the present study, we have used mdr1-type knockout (KO) mice to demonstrate that IEL also utilize mdr1 a, but only preferentially, in that the mdr1 b isoform can be expressed in the absence of mdr1 a expression. We also report that a high level of P-gp activity appears to be necessary for the normal development of certain IEL subpopulations. In specific, while the total number of IEL was relatively unaffected by the absence of mdr1 a expression, the proportions of CD8αβ and TCRαβ+ IEL increased significantly in mdr1 a and mdr1 a/ b KO mice at the expense of CD8αα and TCRγδ+ IEL, respectively. Moreover, these subset alterations also appeared to have functional consequences, in that proliferative, IL-2, and IFN-γ responses of IEL from KO mice were distinct from those of normal IEL. In summary, our data suggest that mdr1 a expression is required for the development of certain IEL subpopulations, most notably TCRγδ+ cells, and thereby indirectly influences the balance of T cell subsets in the intestinal epithelium.