Phenotypic characterization of CD3-7+ cells in developing human intestine and an analysis of their ability to differentiate into T cells

Early-Life Compartmentalization of Immune Cells in Human Fetal Tissues Revealed by High-Dimensional Mass Cytometry

The human fetal immune system must protect the infant against the sudden exposure to a large variety of pathogens upon birth. While it is known that the fetal immune system develops in sequential waves, relatively little is known about the composition of the innate and adaptive immune system in the tissues. Here, we applied high-dimensional mass cytometry to profile the immune system in human fetal liver, spleen, and intestine. With Hierarchical Stochastic Neighbor Embedding (HSNE) we distinguished 177 distinct immune cell clusters, including both previously identified and novel cell clusters. PCA analysis indicated substantial differences between the compositions of the immune system in the different organs. Through dual t-SNE we identified tissue-specific cell clusters, which were found both in the innate and adaptive compartment. To determine the spatial location of tissue-specific subsets we developed a 31-antibody panel to reveal both the immune compartment and surrounding stromal elements through analysis of snap-frozen tissue samples with imaging mass cytometry. Imaging mass cytometry reconstructed the tissue architecture and allowed both the characterization and determination of the location of the various immune cell clusters within the tissue context. Moreover, it further underpinned the distinctness of the immune system in the tissues. Thus, our results provide evidence for early compartmentalization of the adaptive and innate immune compartment in fetal spleen, liver, and intestine. Together, our data provide a unique and comprehensive overview of the composition and organization of the human fetal immune system in several tissues.

Intraepithelial lymphocytes subsets in different forms of celiac disease

AIM

The enumeration of intraepithelial lymphocytes subsets (total, γδ, and CD3(-) IELs) by flow cytometry (FCM), named as IEL lymphogram, constitutes a useful tool for celiac disease (CD) diagnosis. The aim of this study was to quantify IELs by FCM and their diagnostic value to differentiate active, silent and potential CD.

METHODS

Prospective study of 60 active and 20 silent CD patients, and 161 controls in which duodenal biopsy and IEL quantification by FCM was performed.

RESULTS

Active and silent CD patients had significant higher levels of both total and γδ IELs than absent CD patients (P < 0.0001 and P < 0.0001, P = 0.012 and P < 0.011; respectively). Active and silent CD patients had significant lower levels of CD3(-) IELs than absent CD patients (P < 0.047 and P < 0.009, respectively). Moreover, they were lower in silent than in active CD patients (P = 0.002). Changes of IELs subsets were more marked in children than adults active CD. The optimal IEL lymphogram cut off values for active CD diagnosis were: ≥10, ≥15 and ≤9 %, and with better performance characteristics for silent CD: ≥ 11, ≥10 and ≤5 %.

CONCLUSION

The evaluation of IELs subsets by FCM is useful to confirm diagnosis of active and silent CD.

The composition and differentiation potential of the duodenal intraepithelial innate lymphocyte compartment is altered in coeliac disease

OBJECTIVE

Coeliac disease (CD), a gluten-induced enteropathy, alters the composition and function of duodenal intraepithelial T cells. The intestine also harbours four types of CD3-negative intraepithelial lymphocytes (IELs) with largely unknown function: CD56(-)CD127(-), CD56(-)CD127(+), CD56(+)CD127(-) and CD56(+)CD127(+). Here we aimed to gain insight into the potential function of these innate IELs in health and disease.

DESIGN

We determined the phenotypes, relative abundance and differentiation potential of these innate IEL subsets in duodenal biopsies from controls and patients with CD or patients with refractory CD type II (RCDII).

RESULTS

Hierarchical clustering analysis of the expression of 15 natural killer and T cell surface markers showed that innate IELs differed markedly from innate peripheral blood lymphocytes and divided innate IEL subsets into two main branches: a CD127(-) branch expressing high levels of interleukin (IL) 2/15Rβ but no IL-21R, and a CD127(+) branch with the opposite phenotype. While CD was characterised by the contraction of all four innate IEL subsets, a selective expansion of CD56(-)CD127(-) and CD56(-)CD127(+) innate IEL was detected in RCDII. In vitro, in the presence of IL-15, CD56(-)CD127(-) IEL from controls and patients with CD, but not from patients with RCDII, differentiated into functional natural killer and T cells, the latter largely dependent on notch-signalling. Furthermore, compared with non-coeliac controls, CD56(-)CD127(-) IEL from patients with CD expressed more intracellular CD3ε and CD3γ and gave more pronounced T cell differentiation.

CONCLUSIONS

Thus, we demonstrate previously unappreciated diversity and plasticity of the innate IEL compartment and its loss of differentiation potential in patients with RCDII.

The Role of T-Cell Subsets in Chronic Inflammation in Celiac Disease and Inflammatory Bowel Disease Patients: More Common Mechanisms or More Differences?

Background

Chronic intestinal inflammation due to noninfectious causes represents a growing health issue all over the world. Celiac disease as well as inflammatory bowel diseases (IBD) like Crohn's disease and ulcerative and microscopic colitis involve uncontrolled T-cell activation and T-cell-mediated damage as common denominators. Therefore, diagnosis and treatment decisions clearly benefit from the knowledge of the intricacies of the systemic and the local T-cell activity.

Summary

Depending on the cytokine milieu, CD4⁺ T cells can differentiate into proinflammatory T helper 1 (Th1), anti-inflammatory Th2, antimicrobial Th17, pleiotropic Th9, tissue-instructing Th22 cells, and in the regulatory compartment forkhead box protein 3⁺ Treg, suppressive Tr1 or Th3 cells. Additionally, follicular Th cells provide B-cell help in antibody class switching; cytotoxic CD8⁺ T cells target virus-infected or tumor cells. This review discusses our current knowledge on the contribution of defined T-cell subpopulations to establishing and maintaining chronic intestinal inflammation in either of the above entities. It also puts emphasis on the differences in the prevalence of these diseases between Eastern and Western countries.

Key Messages

In celiac disease, the driving role of T cells in the lamina propria and in the epithelium mainly specific for two defined antigens is well established. Differences in genetics and lifestyle between Western and Eastern countries were instrumental in understanding underlying mechanisms. In IBD, the vast amount of potential antigens and the corresponding antigen-specific T cells makes it unlikely to find universal triggers. Increased mucosal CD4⁺ regulatory T cells in all four entities fail to control or abrogate local inflammatory processes. Thus, prevailing differences in the functional T-cell subtypes driving chronic intestinal inflammation in celiac disease and IBD at best allow some overlap in the treatment options for either disease.

Macrochimerism in Intestinal Transplantation: Association With Lower Rejection Rates and Multivisceral Transplants, Without GVHD

Blood chimerism has been reported sporadically among visceral transplant recipients, mostly in association with graft-vs-host disease (GVHD). We hypothesized that a higher degree of mixed chimerism would be observed in multivisceral (MVTx) than in isolated intestinal (iITx) and isolated liver transplant (iLTx) recipients, regardless of GVHD. We performed a longitudinal prospective study investigating multilineage blood chimerism with flow cytometry in 5 iITx and 4 MVTx recipients up to one year posttransplant. Although only one iITx patient experienced GVHD, T cell mixed chimerism was detected in 8 out of 9 iITx/MVTx recipients. Chimerism was significantly lower in the four subjects who displayed early moderate to severe rejection. Pre-formed high-titer donor-specific antibodies, bound in vivo to the circulating donor cells, were associated with an accelerated decline in chimerism. Blood chimerism was also studied in 10 iLTx controls. Among nonsensitized patients, MVTx recipients exhibited greater T and B cell chimerism than either iITx or iLTx recipients. Myeloid lineage chimerism was present exclusively among iLTx and MVTx (6/13) recipients, suggesting that its presence required the hepatic allograft. Our study demonstrates, for the first time, frequent T cell chimerism without GVHD following visceral transplantation and a possible relationship with reduced rejection rate in MVTx recipients.

Immunologic and Hematological Abnormalities in Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a leading cause of mortality in preterm infants. This article reviews the immunologic and hematological abnormalities typically seen in infants with NEC, such as elevated plasma cytokine levels, thrombocytopenia, increased or decreased neutrophil counts, low monocyte counts, and anemia. Some of these findings may provide important diagnostic and prognostic information.

Aberrant mucosal lymphocyte number and subsets in the colon of post-infectious irritable bowel syndrome patients

BACKGROUND

Irritable bowel syndrome (IBS) is characterized by chronic abdominal symptoms such as pain, discomfort, and altered bowel habits. A subset of IBS patients, denoted as post-infectious IBS (PI-IBS) patients, develop symptoms after an enteric infection. Distinct abnormalities in the gut mucosa, including mucosal inflammation, have been proposed to contribute to or be the cause of PI-IBS. This study investigated lymphocyte subsets in PI-IBS patients compared to healthy controls.

MATERIALS AND METHODS

Ten PI-IBS patients and nine healthy controls participated. All PI-IBS patients met the Rome III diagnostic criteria for IBS and reported sustained symptoms at least 1 year after an episode of acute gastroenteritis. Intraepithelial lymphocytes and lamina propria lymphocytes (LPLs), isolated from mucosal tissue samples, were stained and analyzed for a comprehensive set of cell markers using flow cytometry.

RESULTS

The number of LPLs in PI-IBS was significantly increased compared to those in healthy controls (p < 0.05). PI-IBS patients showed significantly increased proportions of CD45RO(+) CD4(+) activated/memory T cells (p < 0.05) and double-positive CD4(+) CD8(+) cells (p < 0.05), respectively, in the lamina propria. The number of CD19(+) LPLs was decreased in PI-IBS patients compared to healthy controls (p < 0.001).

CONCLUSION

This study presents new evidence that PI-IBS is associated with a sustained aberrant mucosal immune response and support future studies of anti-inflammatory or immune-modulating treatments in these patients.

Molecular evidence for a thymus-independent partial T cell development in a FOXN1-/- athymic human fetus

The thymus is the primary organ able to support T cell ontogeny, abrogated in FOXN1(-/-) human athymia. Although evidence indicates that in animal models T lymphocytes may differentiate at extrathymic sites, whether this process is really thymus-independent has still to be clarified. In an athymic FOXN1(-/-) fetus, in which we previously described a total blockage of CD4(+) and partial blockage of CD8(+) cell development, we investigated whether intestine could play a role as extrathymic site of T-lymphopoiesis in humans. We document the presence of few extrathymically developed T lymphocytes and the presence in the intestine of CD3(+) and CD8(+), but not of CD4(+) cells, a few of them exhibiting a CD45RA(+) naïve phenotype. The expression of CD3εεpTα, RAG1 and RAG2 transcripts in the intestine and TCR gene rearrangement was also documented, thus indicating that in humans the partial T cell ontogeny occurring at extrathymic sites is a thymus- and FOXN1-independent process.

FOXN1: A Master Regulator Gene of Thymic Epithelial Development Program

T cell ontogeny is a sophisticated process, which takes place within the thymus through a series of well-defined discrete stages. The process requires a proper lympho-stromal interaction. In particular, cortical and medullary thymic epithelial cells (cTECs, mTECs) drive T cell differentiation, education, and selection processes, while the thymocyte-dependent signals allow thymic epithelial cells (TECs) to maturate and provide an appropriate thymic microenvironment. Alterations in genes implicated in thymus organogenesis, including Tbx1, Pax1, Pax3, Pax9, Hoxa3, Eya1, and Six1, affect this well-orchestrated process, leading to disruption of thymic architecture. Of note, in both human and mice, the primordial TECs are yet unable to fully support T cell development and only after the transcriptional activation of the Forkhead-box n1 (FOXN1) gene in the thymic epithelium this essential function is acquired. FOXN1 is a master regulator in the TEC lineage specification in that it down-stream promotes transcription of genes, which, in turn, regulate TECs differentiation. In particular, FOXN1 mainly regulates TEC patterning in the fetal stage and TEC homeostasis in the post-natal thymus. An inborn null mutation in FOXN1 leads to Nude/severe combined immunodeficiency (SCID) phenotype in mouse, rat, and humans. In Foxn1^−/− nude animals, initial formation of the primordial organ is arrested and the primordium is not colonized by hematopoietic precursors, causing a severe primary T cell immunodeficiency. In humans, the Nude/SCID phenotype is characterized by congenital alopecia of the scalp, eyebrows, and eyelashes, nail dystrophy, and a severe T cell immunodeficiency, inherited as an autosomal recessive disorder. Aim of this review is to summarize all the scientific information so far available to better characterize the pivotal role of the master regulator FOXN1 transcription factor in the TEC lineage specifications and functionality.

Neonatal immune adaptation of the gut and its role during infections

The intestinal tract is engaged in a relationship with a dense and complex microbial ecosystem, the microbiota. The establishment of this symbiosis is essential for host physiology, metabolism, and immune homeostasis. Because newborns are essentially sterile, the first exposure to microorganisms and environmental endotoxins during the neonatal period is followed by a crucial sequence of active events leading to immune tolerance and homeostasis. Contact with potent immunostimulatory molecules starts immediately at birth, and the discrimination between commensal bacteria and invading pathogens is essential to avoid an inappropriate immune stimulation and/or host infection. The dysregulation of these tight interactions between host and microbiota can be responsible for important health disorders, including inflammation and sepsis. This review summarizes the molecular events leading to the establishment of postnatal immune tolerance and how pathogens can avoid host immunity and induce neonatal infections and sepsis.

Meconium microbiota types dominated by lactic acid or enteric bacteria are differentially associated with maternal eczema and respiratory problems in infants

BACKGROUND

Culture-dependent methods have shown that meconium, the newborn's first intestinal discharge, is not sterile, but the diversity of bacteria present in this material needs to be further characterized by means of more sensitive molecular techniques.

OBJECTIVE

Our aims were to characterize molecularly the meconium microbiota in term infants, to assess whether it contributes to the future microbiota of the infants' gastrointestinal tract, and to evaluate how it relates to lifestyle variables and atopy-related conditions.

METHODS

We applied high-throughput pyrosequencing of the 16S rRNA gene to study the meconium microbiota in twenty term newborns from a Spanish birth cohort. For comparison, we characterized the microbiota in fecal samples from seven pregnant women days before delivery and in two series of infant samples spanning the first seven months of life. We also compared our data with vaginal and skin microbiota characterized in independent studies. Different types of meconium microbiota were defined based on taxonomic composition and abundance and their associations with different factors were statistically evaluated.

RESULTS

The meconium microbiota differs from those in adult feces, vagina and skin, but resembles that of fecal samples from young infants. Meconium samples clustered into two types with different bacterial diversity, richness and composition. One of the types was less diverse, dominated by enteric bacteria and associated with a history of atopic eczema in the mother (P = 0.038), whereas the second type was dominated by lactic acid bacteria and associated with respiratory problems in the infant (P = 0.040).

CONCLUSIONS & CLINICAL RELEVANCE

Our findings suggest that the meconium microbiota has an intrauterine origin and participates in gut colonization. Although based on a small population sample, our association analyses also suggest that the type of bacteria detected in meconium is influenced by maternal factors and may have consequences for childhood health.

CD161 DEFINES EFFECTOR T CELLS THAT EXPRESS LIGHT AND RESPOND TO TL1A-DR3 SIGNALING

Expression of NK cell markers identifies pro-inflammatory T cell subsets in the liver and intestinal immune compartments. Specifically, CD161 is expressed on Th17 cells which play an important role in the regulation of mucosal inflammation. In this study, we characterized human peripheral blood CD161+ T cells as an effector population partially resembling a gut T cell phenotype. CD161+ CD4+ T cells express the gut-associated TNF family member, LIGHT, and respond to crosslinking of DR3, a receptor to another gut-associated cytokine, TL1A. Robust IFN-γ production in response to DR3 signaling correlated with enhanced expression of surface DR3 on CD161+ T cells and co-stimulation with IL12 and IL18. CD161+ T cell effector function was directly demonstrated by activation of responder monocytes in co-culture leading to CD40 upregulation and CD14 downregulation. CD161+ T cells reciprocally responded to activated monocytes, inducing expression of activation marker, CD69, and production of IL2 and IFN-γ, further demonstrating effective CD161+ T cell cross-talk with monocytes. Finally, CD161 defined a subset of T cells that co-express CD56, a second NK marker. Our findings implicate human CD161+ T cells in gut-associated signaling mechanisms, and suggest a monocyte mediated effector function in mucosal inflammation.

Celiac disease: how complicated can it get?

In the small intestine of celiac disease patients, dietary wheat gluten and similar proteins in barley and rye trigger an inflammatory response. While strict adherence to a gluten-free diet induces full recovery in most patients, a small percentage of patients fail to recover. In a subset of these refractory celiac disease patients, an (aberrant) oligoclonal intraepithelial lymphocyte population develops into overt lymphoma. Celiac disease is strongly associated with HLA-DQ2 and/or HLA-DQ8, as both genotypes predispose for disease development. This association can be explained by the fact that gluten peptides can be presented in HLA-DQ2 and HLA-DQ8 molecules on antigen presenting cells. Gluten-specific CD4⁺ T cells in the lamina propria respond to these peptides, and this likely enhances cytotoxicity of intraepithelial lymphocytes against the intestinal epithelium. We propose a threshold model for the development of celiac disease, in which the efficiency of gluten presentation to CD4⁺ T cells determines the likelihood of developing celiac disease and its complications. Key factors that influence the efficiency of gluten presentation include: (1) the level of gluten intake, (2) the enzyme tissue transglutaminase 2 which modifies gluten into high affinity binding peptides for HLA-DQ2 and HLA-DQ8, (3) the HLA-DQ type, as HLA-DQ2 binds a wider range of gluten peptides than HLA-DQ8, (4) the gene dose of HLA-DQ2 and HLA-DQ8, and finally,(5) additional genetic polymorphisms that may influence T cell reactivity. This threshold model might also help to understand the development of refractory celiac disease and lymphoma.

Development of mucosal immune function in the intrauterine and early postnatal environment

PURPOSE OF REVIEW

There is recent evidence that immunological priming can start prenatally or in the very early life phase. This review summarizes recent progress in the field of early gut immunology with special attention to factors contributing to the intrauterine and early postnatal development of mucosal immune responses in the gut.

RECENT FINDINGS

Development and maturation of the fetal gut immune system occurs under close control of the maternal environment. Examples include maternal antibodies, cytokines, sCD14 molecules and bacterial antigens. Mouse experiments reveal that activated T cells can be detected already at birth in the fetal gut, which are supposed to be activated by signals from the maternal microbial gut flora. Human milk sCD14 is involved in the immunological priming of the developing gut immune system to Gram-negative bacteria and modulates the microbial recognition system of the gut. The development of food allergies is associated with consumption of food components like polyunsaturated fatty acids acting prenatally or in the early postnatal life span as immunomodulators.

SUMMARY

The new findings highlight the importance of very early life factors for the development of the mucosal immune functions of the gut. Therefore, the gut might be a new target to establish preventive strategies with regard to different immunologic disorders.

Lamina propria c-kit+ immune precursors reside in human adult intestine and differentiate into natural killer cells

BACKGROUND AND AIMS

Recent studies have revealed that murine intestinal mucosa contains several kinds of lineage markers (lin)(-) c-kit(+) immune precursor cells. However, immune precursors in the human adult intestine have not been studied extensively.

METHODS

Lamina propria mononuclear cells and intraepithelial lymphocytes from surgically resected human adult intestine were examined for the surface antigen expression and cytokine profile by immunohistochemistry and flow cytometry. The transcriptional profile of these cells was analyzed by reverse-transcription polymerase chain reaction. The phenotypic and functional characterization of the in vitro differentiating cells from the precursors was examined by flow cytometry.

RESULTS

We identified lin(-) c-kit(+) cells scattered throughout lamina propria of the human adult intestine. These intestinal immune precursors expressed CD34, CD38, CD33, interleukin-2R alpha, and interleukin-7R alpha, and they had much more abundant expression of Id2, PU.1, SpiB1, and lymphotoxin than thymocytes. The lin(-) c-kit(+) immune precursors mainly differentiated into CD56(+) c-kit(dim) cells during in vitro culture. These in vitro differentiating cells corresponded to intestinal natural killer (NK) cells, which had distinct characteristics from their peripheral counterparts, such as CD83 and integrin alpha(E) expression, less cytotoxic activity, and higher interferon-gamma production. Furthermore, both c-kit(dim) cells and NK cells were increased in lamina propria of Crohn's disease, although there was no change for peripheral blood NK cells.

CONCLUSIONS

The human intestine may have the unique NK cell differentiation system, which may contribute to maintenance of immune homeostasis in the intestine.

CD56 marks an effector T cell subset in the human intestine

T cells are key mediators of intestinal immunity, and specific T cell subsets can have differing immunoregulatory roles in animal models of mucosal inflammation. In this study, we describe human CD56+ T cells as a morphologically distinct population expressing a mature, nonproliferative phenotype that is frequent in the gut. Enhanced potential for IFN-gamma and TNF synthesis suggested a proinflammatory function, and we directly demonstrate effector function mediated by direct T-T interaction with responder cells in vitro. CD56+ T cells from peripheral blood responded to the gut-related CD2 signal, and were necessary for effective CD2-mediated proliferation of peripheral blood CD56- T cells. Our findings associate CD56+ T cells with the intestinal immune compartment and suggest a putative effector function in human mucosal immunity.

Reduced chemokine receptor 9 on intraepithelial lymphocytes in celiac disease suggests persistent epithelial activation

BACKGROUND & AIMS

Celiac disease is caused by an inappropriate immune response to dietary gluten, with increased epithelial lymphocyte infiltration in the duodenum/jejunum as a hallmark. The chemokine receptor 9 (CCR9) is a small intestinal homing receptor normally found on most mucosal T cells in this organ. Because CCR9 expression appears to be activation dependent, we examined CCR9 on duodenal T cells from untreated and treated (gluten-free diet) patients with celiac disease and healthy controls.

METHODS

Duodenal biopsy specimens and blood samples were obtained for histologic analysis and flow-cytometric CCR9 analysis of isolated lymphocytes. CCR9 expression after activation was studied in peripheral blood T cells from healthy volunteers.

RESULTS

The median number of CCR9(+) cells among CD3(+) T cells in epithelium and lamina propria, respectively, was 56% and 48% in controls, 11% and 40% in treated patients, and 1% and 8% in untreated patients. Significant differences occurred between controls and treated or untreated patients in the epithelium but only between controls and untreated patients in the lamina propria (P=.008, all comparisons). No such differences were seen in peripheral blood, but stimulation with phorbol myristate acetate and ionomycin and, to a lesser extent, stimulation via NKG2D reduced the CCR9 expression on blood T cells.

CONCLUSIONS

CCR9 expression is reduced on epithelial and lamina propria T cells in untreated celiac disease. Down-regulation of CCR9 persists in intraepithelial T cells from well-treated patients. This suggests ongoing immune activation preferentially within the epithelium.

Invariant natural killer T cells in asthma and chronic obstructive pulmonary disease

BACKGROUND

The number of type 2 helper CD4+ T cells is increased in the airways of persons with asthma. Whether the majority of these cells are class II major-histocompatibility-complex-restricted cells or are among the recently identified CD1d-restricted invariant natural killer T cells is a matter of controversy. We studied the frequency of invariant natural killer T cells in the airways of subjects with mild or moderately severe asthma to investigate the possibility of an association between the number of invariant natural killer T cells in the airway and disease severity. We also studied whether an increased number of these cells is a feature of chronic obstructive pulmonary disease (COPD).

METHODS

We enumerated invariant natural killer T cells by flow cytometry with the use of CD1d tetramers loaded with alpha-galactosylceramide and antibodies specific to the invariant natural killer T-cell receptor in samples of bronchoalveolar-lavage fluid, induced sputum, and bronchial-biopsy specimens obtained from subjects with mild or moderately severe asthma, subjects with COPD, and healthy control subjects. Real-time polymerase-chain-reaction analysis was performed on bronchoalveolar-lavage cells for evidence of gene expression of the invariant natural killer T-cell receptor.

RESULTS

Fewer than 2% of the T cells obtained from all subjects on airway biopsy, bronchoalveolar lavage, and sputum induction were invariant natural killer T cells, with no significant differences among the three groups of subjects. No expression of messenger RNA for the invariant natural killer T-cell-receptor domains Valpha24 and Vbeta11 was detected in bronchoalveolar-lavage cells from subjects with asthma.

CONCLUSIONS

Invariant natural killer T cells are found in low numbers in the airways of subjects with asthma, subjects with COPD, and controls.

Age-related variation of intraepithelial lymphocytes subsets in normal human duodenal mucosa

The enumeration of intestinal intraepithelial lymphocytes (IELs), and the phenotyping of CD3+CD 103+ (TcRalphabeta, TcRgammadelta) and CD3-CD103+ IEL subsets constitute useful diagnostic tools for the correct interpretation of the mucosal histology of duodenal/jejunal biopsies in many pathological conditions of the small intestine, particularly celiac disease (CD). This work evaluates the ranges of duodenal IEL counts by flow cytometry in healthy mucosa from pediatric and adult controls, establishing normal reference values for CD3+ TcRgammadelta and CD3- subsets and their variation with age. Seventy-four pediatric controls and 36 adult controls were identified on the basis of their normal histology from more than 1,000 duodenal diagnostic biopsies performed in Caucasian subjects. Total IEL counts and IEL subsets ("IEL lymphogram") were analyzed by four-color flow cytometry (FCM). IEL represent 7.7% +/- 0.4 (mean +/- SE) and 8.5% +/- 0.5 of the cells isolated from the epithelium in the pediatric and adult series, respectively. The upper normal range, considered as the 97 percentile, is 14% in pediatrics and 15% in adults. No significant difference was observed between TcRgammadeltaIEL percentages in children (6.9% +/- 0.5 of the total IELs) and adults (6.6% +/- 0.8). However, the density of CD3- IELs is significantly higher (p < 0.001) in the mucosa from controls under 3 years (50.2% +/- 2.6) than in adults (25.5% +/- 2.1). IEL lymphogram by flow cytometry is an easy, quick and reliable analysis performed in one of the biopsy specimens obtained during a diagnostic endoscopy, and confers specificity to the histopathological findings. IEL counts below 14% in children and 15% in adults should be considered within a normal range in the evaluation of duodenal mucosa by FCM. No differences with age were observed with respect to TcRgammadeltaIEL, while the CD3- IEL fraction was significantly higher on children under 3 years, with a trend to increase again in the elderly.

Effects of microflora on the neonatal development of gut mucosal T cells and myeloid cells in the mouse

Colonization with commensal flora in very early life may profoundly influence intestinal lymphoid development and bias later immune responses. We defined gut-homing T cell phenotypes and the influence of flora on intestinal immune development in mice. Intestinal T cells were phenotyped and quantified in conventional (CV), germfree (GF) and conventionalized germfree (GF/CV) neonatal mice by immunohistochemistry. Mucosal adressin cell adhesion molecule 1 (MAdCAM-1) was expressed by mucosal vessels at birth in CV and GF mice and was more prevalent in CV than GF small intestine, but was distributed similarly and did not change with age. Less MAdCAM-1 was expressed in the colon; its distribution became restricted after weaning, with no difference between CV and GF mice. CD3(+)beta(7) (+) cells were present in similar numbers in CV and GF intestine at birth. They were CD62L(-) in CV mice and were accompanied by further CD3(+)beta(7) (+)CD62L(-) T cells as development progressed, but in GF and GF/CV intestine they expressed CD62L and numbers did not change. IEL numbers increased at weaning in CV mice in both small and large intestine, but showed delayed development in GF intestine. Macrophages were present at high levels from birth in GF intestine, but dendritic cells did not develop until day 16. Thus, fetus-derived T cells seed the intestinal lamina propria before birth via beta-MadCAM interactions. Their activation status depends on the microbiological status of the dam, and without a commensal flora they remain naive. We propose that these cells regulate antigen responsiveness of the developing mucosal T cell pool.

Development of human lymphoid cells

The lymphocytes, T, B, and NK cells, and a proportion of dendritic cells (DCs) have a common developmental origin. Lymphocytes develop from hematopoietic stem cells via common lymphocyte and various lineage-restricted precursors. This review discusses the current knowledge of human lymphocyte development and the phenotypes and functions of the rare intermediate populations that together form the pathways of development into T, B, and NK cells and DCs. Clearly, development of hematopoietic cells is supported by cytokines. The studies of patients with genetic deficiencies in cytokine receptors that are discussed here have illuminated the importance of cytokines in lymphoid development. Lineage decisions are under control of transcription factors, and studies performed in the past decade have provided insight into transcriptional control of human lymphoid development, the results of which are summarized and discussed in this review.