IL-7 prevents both caspase-dependent and -independent pathways that lead to the spontaneous apoptosis of i-IEL

The Broad Immunomodulatory Effects of IL-7 and Its Application In Vaccines

Interleukin-7 (IL-7) is produced by stromal cells, keratinocytes, and epithelial cells in host tissues or tumors and exerts a wide range of immune effects mediated by the IL-7 receptor (IL-7R). IL-7 is primarily involved in regulating the development of B cells, T cells, natural killer cells, and dendritic cells via the JAK-STAT, PI3K-Akt, and MAPK pathways. This cytokine participates in the early generation of lymphocyte subsets and maintain the survival of all lymphocyte subsets; in particular, IL-7 is essential for orchestrating the rearrangement of immunoglobulin genes and T-cell receptor genes in precursor B and T cells, respectively. In addition, IL-7 can aid the activation of immune cells in anti-virus and anti-tumor immunity and plays important roles in the restoration of immune function. These biological functions of IL-7 make it an important molecular adjuvant to improve vaccine efficacy as it can promote and extend systemic immune responses against pathogens by prolonging lymphocyte survival, enhancing effector cell activity, and increasing antigen-specific memory cell production. This review focuses on the biological function and mechanism of IL-7 and summarizes its contribution towards improved vaccine efficacy. We hope to provide a thorough overview of this cytokine and provide strategies for the development of the future vaccines.

Interleukin-7 Dose-Dependently Restores Parenteral Nutrition–Induced Gut-Associated Lymphoid Tissue Cell Loss but Does Not Improve Intestinal Immunoglobulin A Levels

BACKGROUND

Without enteral nutrition, the mass and function of gut-associated lymphoid tissue (GALT), a center of systemic mucosal immunity, are reduced. Therefore, new therapeutic methods, designed to preserve mucosal immunity during parenteral nutrition (PN), are needed. Our recent study revealed that exogenous interleukin-7 (IL-7; 1 microg/kg twice a day) restores the GALT cell mass lost during intravenous (IV) PN but does not improve secretory immunoglobulin A (IgA) levels. Herein, we studied the IL-7 dose response to determine the optimal IL-7 dose for recovery of GALT mass and function during IV PN. We hypothesized that a high dose of IL-7 would increase intestinal IgA levels, as well as GALT cell numbers.

METHODS

Male mice (n = 42) were randomized to chow, IL-7-0, IL-7-0.1, IL-7-0.33, IL-7-1 and IL-7-3.3 groups and underwent jugular vein catheter insertion. The IL-7 groups were fed a standard PN solution and received IV injections of normal saline (IL-7-0), 0.1, 0.33, 1, or 3.3 microg/kg of IL-7 twice a day. The chow group was fed chow ad libitum. After 5 days of treatment, the entire small intestine was harvested and lymphocytes were isolated from Peyer's patches (PPs), intraepithelial (IE) spaces, and the lamina propria (LP). The lymphocytes were counted and phenotypes determined by flow cytometry (alphabetaTCR, gammadeltaTCR, CD4, CD8, B cell). IgA levels of small intestinal washings were also examined using ELISA (enzyme-linked immunoabsorbent assay).

RESULTS

IL-7 dose-dependently increased total lymphocyte numbers in PPs and the LP. The number of lymphocytes harvested from IE spaces reached a plateau at 1 microg/kg of IL-7. There were no significant differences in any phenotype percentages at any GALT sites among the groups. IgA levels of intestinal washings were significantly higher in the chow group than in any of the IL-7 groups, with similar levels in all IL-7 groups.

CONCLUSIONS

Exogenous IL-7 dose-dependently reverses PN-induced GALT cell loss, with no major changes in small intestinal IgA levels. IL-7 treatment during PN appears to have beneficial effects on gut immunity, but other therapeutic methods are needed to restore secretory IgA levels.

Notch Signaling Regulates the Homeostasis of Tissue-Restricted Innate-like T Cells

Although Notch signaling plays important roles in lineage commitment and differentiation of multiple cell types including conventional T cells, nothing is currently known concerning Notch function in innate-like T cells. We have found that the homeostasis of several well-characterized populations of innate-like T cells including invariant NKT cells (iNKT), CD8ααTCRαβ small intestinal intraepithelial lymphocytes, and innate memory phenotype CD8 T cells is controlled by Notch. Notch selectively regulates hepatic iNKT cell survival via tissue-restricted control of B cell lymphoma 2 and IL-7Rα expression. More generally, Notch regulation of innate-like T cell homeostasis involves both cell-intrinsic and -extrinsic mechanisms and relies upon context-dependent interactions with Notch ligand-expressing fibroblastic stromal cells. Collectively, using conditional ablation of Notch receptors on peripheral T cells or Notch ligands on putative fibroblastic stromal cells, we show that Notch signaling is indispensable for the homeostasis of three tissue-restricted populations of innate-like T cells: hepatic iNKT, CD8ααTCRαβ small intestinal intraepithelial lymphocytes, and innate memory phenotype CD8 T cells, thus supporting a generalized role for Notch in innate T cell homeostasis.

Co-culture with intestinal epithelial organoids allows efficient expansion and motility analysis of intraepithelial lymphocytes

BACKGROUND

Intraepithelial lymphocytes (IELs) in the intestine play important roles in the regulation of local immune responses. Although their functions have been studied in a variety of animal experiments, in vitro studies on spatiotemporal behaviors of IELs and their interaction with intestinal epithelial cells (IECs) have been hampered due to the lack of a suitable culture system. In this study, we aimed at developing a novel co-culture system of IELs with IECs to investigate dynamic interaction between these two populations of cells in vitro.

METHODS

We optimized experimental conditions under which murine IELs can be efficiently maintained with IECs cultured as three-dimensional organoids. We then tested the effect of IL-2, IL-7, and IL-15 on the maintenance of IELs in this co-culture system. By time-lapse imaging, we also examined the dynamic behaviors of IELs.

RESULTS

IELs can be expanded with epithelial organoids in the presence of IL-2, IL-7, and IL-15. IELs were efficiently maintained within and outside of organoids showing a ~four-fold increase in both αβT and γδT IELs for a period of 2 weeks. Four-dimensional fluorescent imaging revealed an active, multi-directional movement of IELs along the basolateral surface of IECs, and also their inward or outward migration relative to organoid structures. Cell tracking analysis showed that αβT and γδT IELs shared indistinguishable features with regard to their dynamics.

CONCLUSIONS

This novel co-culture method could serve as a unique tool to investigate the motility dynamics of IELs and their temporal and spatial interaction with IECs in vitro.

Role of the intestinal cytokine microenvironment in shaping the intraepithelial lymphocyte repertoire

Local resident IELs are composed of distinct subsets of T cells with potent cytolytic and immunoregulatory capacities. As IELs are located within this unique interface between the core of the body and the outside environment, the specific development and function of intestinal IELs must be tightly regulated. To accomplish this, the cytokine microenvironment of the intestine has evolved sophisticated mechanisms that modulate the phenotype, ontogeny, and function of these cells. In this review, we summarize the evidence demonstrating the origin of certain intestinal cytokines, including IL-7, IL-15, IL-2, TGF-β, and SCF and discuss what influence such cytokines may have on IELs. Moreover, we review data suggesting that the abnormal expression of cytokines that leads to the heightened activation of IELs may also contribute to immunopathological responses or exacerbate inflammatory diseases, such as IBD and celiac disease, or promote cancer development and progression.

ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context

This report provides a review of early and late effects of radiation in normal tissues and organs with respect to radiation protection. It was instigated following a recommendation in Publication 103 (ICRP, 2007), and it provides updated estimates of 'practical' threshold doses for tissue injury defined at the level of 1% incidence. Estimates are given for morbidity and mortality endpoints in all organ systems following acute, fractionated, or chronic exposure. The organ systems comprise the haematopoietic, immune, reproductive, circulatory, respiratory, musculoskeletal, endocrine, and nervous systems; the digestive and urinary tracts; the skin; and the eye. Particular attention is paid to circulatory disease and cataracts because of recent evidence of higher incidences of injury than expected after lower doses; hence, threshold doses appear to be lower than previously considered. This is largely because of the increasing incidences with increasing times after exposure. In the context of protection, it is the threshold doses for very long follow-up times that are the most relevant for workers and the public; for example, the atomic bomb survivors with 40-50years of follow-up. Radiotherapy data generally apply for shorter follow-up times because of competing causes of death in cancer patients, and hence the risks of radiation-induced circulatory disease at those earlier times are lower. A variety of biological response modifiers have been used to help reduce late reactions in many tissues. These include antioxidants, radical scavengers, inhibitors of apoptosis, anti-inflammatory drugs, angiotensin-converting enzyme inhibitors, growth factors, and cytokines. In many cases, these give dose modification factors of 1.1-1.2, and in a few cases 1.5-2, indicating the potential for increasing threshold doses in known exposure cases. In contrast, there are agents that enhance radiation responses, notably other cytotoxic agents such as antimetabolites, alkylating agents, anti-angiogenic drugs, and antibiotics, as well as genetic and comorbidity factors. Most tissues show a sparing effect of dose fractionation, so that total doses for a given endpoint are higher if the dose is fractionated rather than when given as a single dose. However, for reactions manifesting very late after low total doses, particularly for cataracts and circulatory disease, it appears that the rate of dose delivery does not modify the low incidence. This implies that the injury in these cases and at these low dose levels is caused by single-hit irreparable-type events. For these two tissues, a threshold dose of 0.5Gy is proposed herein for practical purposes, irrespective of the rate of dose delivery, and future studies may elucidate this judgement further.

Nutrition and gut immunity

The human intestine contains huge amounts of nonpathologic bacteria surviving in an environment that is beneficial to both the host and the bacterial populations. When short pauses in oral intake occur with minimal alterations in the mucosa-microbial interface, critical illness, with its attendant acidosis, prolonged gastrointestinal tract starvation, exogenous antibiotics, and breakdown in mucosal defenses, renders the host vulnerable to bacterial challenge and also threatens the survival of the bacteria. This review examines the altered innate and adaptive immunologic host defenses that occur as a result of altered oral or enteral intake and/or injury.

Relevance of target cell-induced apoptosis as mechanism of resistance against natural killer cells

Natural killer (NK) cells contribute to the graft-versus-leukemia effect after allogeneic stem cell transplantation. However, the efficacy of NK cell-mediated tumor cell lysis is limited due to target cell resistance, and target cell-induced apoptosis (TiA) was proposed to contribute to differences in susceptibility to NK cells. Here we analyzed the effects of target cells on the apoptosis of cytokine-activated NK cells in vitro. We found no association of target cell susceptibility and TiA of NK cells in an array of human and murine target-effector cell combinations. Incubation of NK cells with caspase inhibitors blocked TiA incompletely, indicating that TiA is partly based on caspase-independent mechanisms. Modulating NK cell susceptibility against TiA by caspase inhibition did not influence cytotoxic efficacy. Furthermore, we found cytotoxic potential of NK cells to be markedly decreased following first target cell contact. Exhaustion of NK cell activity by first target cell contact was, however, not mediated by TiA. In addition, we found no relevant TiA by lymphoma cell lines against activated murine NK cells. We conclude that TiA represents only a minor factor of target cell resistance against NK cell-mediated cytolysis.

Specific overexpression of IL-7 in the intestinal mucosa: the role in intestinal intraepithelial lymphocyte development

IL-7 plays a crucial role in controlling T cell development and homeostasis. Since IL-7 may be derived from extraintestinal sources, and exogenous IL-7 broadly affects lymphoid populations, the actions of epithelial cell (EC)-derived IL-7 are not fully understood. The effect of intestinal specific expression of IL-7 on intestinal mucosal lymphocytes was investigated by using an IL-7 transgenic mouse model. We generated an intestinal EC-specific overexpressing IL-7 transgenic mouse model (IL-7(vill)) and compared their phenotype and function to wild-type C57BL/6J mice. EC-derived IL-7 overexpression was found to be exclusively in the small and large intestine. Numbers and subtypes of mucosal lymphocytes, including intraepithelial lymphocytes (IEL) and lamina propria lymphocytes (LPL), significantly changed in IL-7(vill) mice. From a functional standpoint, IEL proliferation also significantly increased in IL-7(vill) mice. IEL cytokine expression significantly changed in both T cell receptor (TCR)-alphabeta(+) and TCR-gammadelta(+) IEL subpopulations, including a significant increase in IFN-gamma and TNF-alpha as well as an increase in keratinocyte growth factor expression. EC expression of CD103 (integrin alpha(E)beta(7)), the ligand of E-cadherin, markedly upregulated and may account for a mechanism of the massive expansion of IEL in transgenic mice. Systemic lymphoid populations did not change in transgenic mice. IL-7 overexpression by intestinal EC significantly affected IEL phenotype and function. These results offer insight into the role of IL-7 in IEL development and suggest a critical role of EC-derived expression of IL-7 in the phenotype and function of IEL.

Intestinal epithelial cell-derived interleukin-7: A mechanism for the alteration of intraepithelial lymphocytes in a mouse model of total parenteral nutrition

Total parenteral nutrition (TPN), with the absence of enteral nutrition, results in profound changes to both intestinal epithelial cells (EC) as well as the adjacent intraepithelial lymphocyte (IEL) population. Intestinal EC are a rich source of IL-7, a critical factor to support the maintenance of several lymphoid tissues, and TPN results in marked EC changes. On this basis, we hypothesized that TPN would diminish EC-derived IL-7 expression and that this would contribute to the observed changes in the IEL population. Mice received enteral food and intravenous crystalloid solution (control group) or TPN. TPN administration significantly decreased EC-derived IL-7 expression, along with significant changes in IEL phenotype; decreased IEL proliferation; and resulted in a marked decrease in IEL numbers. To better determine the relevance of TPN-related changes in IL-7, TPN mice supplemented with exogenous IL-7 or mice allowed ad libitum feeding and treated with exogenous administration of anti-IL-7 receptor (IL-7R) antibody were also studied. Exogenous IL-7 administration in TPN mice significantly attenuated TPN-associated IEL changes, whereas blocking IL-7R in normal mice resulted in several similar changes in IEL to those observed with TPN. These findings suggest that a decrease in EC-derived IL-7 expression may be a contributing mechanism to account for the observed TPN-associated IEL changes.

EXOGENOUS INTERLEUKIN 7 AFFECTS GUT-ASSOCIATED LYMPHOID TISSUE IN MICE RECEIVING TOTAL PARENTERAL NUTRITION

In the absence of enteral nutrient delivery, gut-associated lymphoid tissue (GALT) mass and function are reduced. The purpose of this study was to examine whether exogenous interleukin (IL)-7 treatment reverses intravenous (IV)-total parenteral nutrition (TPN)-induced changes in GALT, immunoglobulin (Ig) A levels, and gut barrier function. Eighty-nine mice were randomized to chow, TPN, or TPN + IL-7 (1 microg/kg, administered IV twice a day) and treated for 5 days. The entire small intestine was harvested and lymphocytes were isolated from Peyer's patches (PPs), intraepithelial (IE) spaces, and the lamina propria (LP). Small intestinal and bronchoalveolar IgA levels were measured. Proximal and distal small intestinal levels of IgA-stimulating (IL-10) and IgA-inhibiting (IFNgamma) cytokines were determined with enzyme-linked immunoabsorbant assay. Moreover, 1 x 10 live Pseudomonas aeruginosa were delivered by gavage and survival was observed. TPN decreased total cell yields from PPs, IE spaces, and the LP compared with the chow group. IL-7 treatment restored cell numbers. PP CD4+, PP CD8+, IE gammadeltaTCR+, and LP CD4+ cell numbers were higher in the TPN + IL-7 group than in the TPN group. Secretory IgA levels were lower in the TPN and TPN + IL-7 than in the chow group. In the distal small intestine, IFNgamma levels were similar in the three groups, whereas IL-10 levels were reduced in the TPN and TPN + IL-7 groups relative to the chow group. Survival times were reduced in the TPN compared with the chow group, but IL-7 treatment significantly improved survival. Thus, exogenous IL-7 does not improve secretory IgA levels, nor are there any remarkable effects on levels of gut IgA-mediating cytokines. However, IL-7 treatment during TPN reverses TPN-induced GALT atrophy and improves survival in a gut-derived sepsis model.

Interleukin-7 administration alters intestinal intraepithelial lymphocyte phenotype and function in vivo

BACKGROUND

Interleukin-7 (IL-7) plays a crucial role in controlling T-cell development and homeostasis. IL-7 knock out and IL-7 receptor knock out mice show distinct declines in absolute numbers of the intestinal intraepithelial lymphocytes (IEL). Therefore, we hypothesized that exogenous administration of IL-7 would alter IEL phenotype and function.

METHODS

Adult C57BL/6J mice were treated with IL-7 or saline. Mice were euthanized at day 7. Cytokine and keratinocyte growth factor (KGF) expressions were measured with RT-PCR. IEL phenotype was studied with flow cytometry. Finally, to address the association of endogenous epithelial cell (EC)-derived IL-7 and IEL, confocal microscopy was used to observe co-localization of IL-7 to IEL subpopulations.

RESULTS

IL-7 administration significantly increased IEL numbers. CD8alphabeta+ IEL increased 3.2-fold, CD8+CD44+ IEL increased 1.3-fold, and alphabeta-T-cell receptor (TCR)+ IEL increased 1.3-fold. IL-7 administration also significantly changed both alphabeta-TCR+ IEL- and gammadelta-TCR+ IEL-derived cytokine expressions. Interestingly, IL-7 administration also led to a significant increase in KGF expression. Confocal microscopy showed a high level of co-localization between the alphabeta-TCR+ IEL and EC-derived IL-7. gammadelta-TCR+ IEL showed a lower level, but still significant, co-localization.

CONCLUSION

IL-7 administration significantly affected IEL phenotype and function. The observed co-localization suggests that there is a close IEL-EC cross-communication mediated by EC-derived IL-7 expression.

Cholera toxin induces a transient depletion of CD8+ intraepithelial lymphocytes in the rat small intestine as detected by microarray and immunohistochemistry

Cholera toxin (CT), besides causing intestinal hypersecretion after intragastric administration or during cholera infection, affects a multitude of regulatory mechanisms within the gut mucosal network, including T cells. By use of microarray screening, real-time PCR, and immunohistochemistry, we demonstrate here a rapid depletion of jejunal CD8(+) intraepithelial lymphocytes (IEL) in rats after intragastric CT challenge. This depletion may depend on CT-induced migration of IEL, since it was associated with a progressive decrease of CD8(+) cells in the epithelium and a contemporary transient increase of such cells, preferentially at the base of the villi, in the lamina propria. A significant decrease in the total number of villous CD8(+) cells at 6 and 18 h after CT challenge was detected; this possibly reflects an efflux from the jejunal mucosa. The kinetics of the CD8(+) IEL demonstrate the return to normal intraepithelial position at original numbers already 72 h after the single CT dose. The induced migration seems to be dependent on the enzymatic A-subunit of CT, since challenge with neither sorbitol nor CT B-subunit did mimic the effects of CT on CD8(+) IEL. Furthermore, a decrease in the level of both RANTES transcript and protein was detected, most likely as a consequence of the CT-induced migration of CD8(+) IEL. These results point to a complex interaction between CT, epithelial cells, and IEL, resulting in a disturbance of the gut homeostasis, which might have relevance for the strong immunomodulatory effects of intragastrically administered CT.

In vivo corticosterone administration at levels occurring with intense exercise does not induce intestinal lymphocyte apoptosis in mice

Intestinal lymphocyte apoptosis can occur following physiological and pathophysiological stress as well as exhaustive exercise. In this study we investigated whether corticosterone (CORT) administration at physiological concentrations observed following strenuous exercise induces intestinal lymphocyte apoptosis and cell loss in mice. CORT injection (14 mg/kg; i.p.) caused a four-fold increase in plasma CORT concentrations, but did not affect intestinal lymphocyte cell loss or alter baseline intestinal lymphocyte apoptosis, as measured by phosphatidylserine externalization, cell viability, mitochondrial membrane depolarization, caspase 3, Bcl-2 and cytosolic cytochrome c protein levels. These findings indicate that CORT at levels observed following strenuous exercise is not involved in intestinal lymphocyte apoptosis and cell loss.

Adrenalectomy in mice does not prevent loss of intestinal lymphocytes after exercise

Exhaustive exercise is associated with an increase in circulating glucocorticoids (GCs), lymphocyte apoptosis, and a reduction in intestinal lymphocyte number. The present study examined the role of GCs on the numerical changes seen in intestinal lymphocytes after exercise. Female C57BL/6 mice were bilaterally adrenalectomized (ADX; n = 18) or given sham surgery (Sham; n = 18) and assigned to one of three exercise conditions: treadmill running (28 m/min, 90 min, 2 degrees slope) and killed immediately or after 24 h recovery, or not exercised and killed immediately after 90-min exposure to the treadmill environment. Lymphocytes were isolated from the intestines with CD45(+) cells collected by positive selection using magnetic bead separation columns, and lymphocyte subpopulations were analyzed by flow cytometry for CD45(+), CD3alphabeta(+), CD3gammadelta(+), CD8beta(+), CD8alpha(+), CD4(+), and NK(+) phenotypic markers. ADX mice had significantly more intestinal CD45(+) leukocytes (P < 0.05) and CD3alphabeta(+) (P < 0.05), CD3gammadelta(+) (P < 0.01), CD8alpha(+) (P < 0.001), and NK(+) (P < 0.05) intestinal lymphocytes than Sham mice. There was a significant effect of exercise condition on total intestinal CD45(+) leukocytes (P < 0.01) and CD3alphabeta(+) (P < 0.05), CD8alpha(+) (P < 0.001), and CD4(+) (P < 0.05) intestinal lymphocytes, with fewer cells at 24 h postexercise compared with the other treatment conditions. There were no surgical x exercise interaction effects on the CD3 and CD8 phenotype numbers. Plasma corticosterone was virtually nil in ADX mice regardless of exercise condition but was significantly elevated in Sham mice immediately postexercise (P < 0.001). The data indicate that ADX does not prevent the loss of lymphocytes from the intestinal mucosa 24 h after strenuous exercise and GCs are not directly causal in the leukopenia of exercise.

Intestinal TSH production is localized in crypt enterocytes and in villus 'hotblocks' and is coupled to IL-7 production: evidence for involvement of TSH during acute enteric virus infection

The immune and neuroendocrine systems have been shown to work conjointly in a number of ways. One aspect of this has to do with a potential role for thyroid stimulating hormone (TSH) in the regulation of the mucosal immune system, although the mechanisms by which this occurs remain vague. To more thoroughly understand how TSH participates in intestinal intraepithelial lymphocyte (IEL) development and immunity, experiments have been conducted to define local sites of intestinal TSH production, and to characterize changes that occur in the synthesis of TSH during acute enteric virus infection. Here, we demonstrate that TSH in the small intestine is specifically localized to regions below villus crypts as seen by immunocytochemical staining, which revealed high-level TSH staining in lower crypts in the absence of IL-7 staining, and TSH and IL-7 co-staining in upper crypt regions. Additionally, prominent TSH staining was evident in TSH 'hotblocks' sparsely dispersed throughout the epithelial layer. In rotavirus-infected mice, the TSH staining pattern differed significantly from that of non-infected animals. Notably, at 2 and 3 days post-infection, TSH expression was high in and near apical villi where virus infection was greatest. These findings lend credence to the notion that TSH plays a role both in the development of intestinal T cells, and in the process of local immunity during enteric virus infection.

IL-15 is superior to IL-2 in the generation of long-lived antigen specific memory CD4 and CD8 T cells in rhesus macaques

Using tetanus toxoid (TT) and influenza (Flu) immunization of rhesus macaques as a model, the effect of IL-2 and IL-15 on the generation and maintenance of antigen specific memory T cells was evaluated following primary and secondary immunization. Daily cytokine administration expanded primarily effector but not memory cells, while spacing cytokine administration to q3-7 days markedly enhanced TT and Flu specific memory responses. Following primary immunization, TT specific CD4 and influenza matrix protein (Flu-MP) specific CD8 effector responses were enhanced by IL-2 administration but CD8 specific memory responses were no different from cytokine non-treated monkeys. In contrast, expansion of Flu specific CD8 cells with IL-15 was only modest but resulted in significantly elevated levels of memory cells at 6 months. IL-15 also significantly enhanced early and late TT specific CD4 responses. The highest levels of primary effector and memory T cells were observed following alternate administration of both IL-2 and IL-15. Following booster immunization, however, only IL-15 appeared able to enhance CD8 T cell responses while IL-2 or IL2/IL-15 administration were less effective.

Isolation of human small bowel intraepithelial lymphocytes by annexin V-coated magnetic beads

Human intestinal intraepithelial lymphocytes (IEL) are important effector cells of the mucosal immune system and their study is hampered by the difficulty of their isolation. The molecular study of enriched samples of IEL is mandatory in the diagnosis of enteropathy-associated T-cell lymphoma and refractory celiac sprue. In order to isolate human small bowel IEL, we took advantage of the stress that intestinal epithelial cells (IEC) suffer during the conventional initial steps of IEL isolation, which induces their apoptosis but not that of IEL. After cell individualization by dithiothreitol and ethylenediamine tetraacetic acid, two-thirds of human IEC can be stained with Annexin-V due to their surface exposure of phosphatidyl serine, a sign of apoptosis. This percentage increases to 95% after performing a density gradient to enrich for IEL. This allows for the use of Annexin-V-coated magnetic beads, originally designed for the removal of dead cells from cell cultures, to obtain >95% pure, 99% viable and untouched IEL after two rounds of depletion. This simple procedure has proven useful for the isolation of human IEL for functional and molecular studies and can conceivably facilitate the diagnosis of intestinal lymphoid malignancies that rely upon the study of pure IEL preparations.

Rapamycin is active against B-precursor leukemia in vitro and in vivo, an effect that is modulated by IL-7-mediated signaling

A balance between survival and apoptotic signals regulates B cell development. These signals are tightly regulated by a host of molecules, including IL-7. Abnormal signaling events may lead to neoplastic transformation of progenitor B cells. Signal transduction inhibitors potentially may modulate these abnormal signals. Inhibitors of the mammalian target of rapamycin (mTOR) such as rapamycin have been used as immunosuppressive agents. We hypothesized that rapamycin might demonstrate activity against B-precursor acute lymphoblastic leukemia. We have found that rapamycin inhibited growth of B-precursor acute lymphoblastic leukemia lines in vitro, with evidence of apoptotic cell death. This growth inhibition was reversible by IL-7. One candidate as a signaling intermediate cross-regulated by rapamycin and IL-7 was p70 S6 kinase. Rapamycin also demonstrated in vivo activity in E mu-ret transgenic mice, which develop pre-B leukemia/lymphoma: E mu-ret transgenic mice with advanced disease treated daily with rapamycin as a single agent showed a >2-fold increase in length of survival as compared with symptomatic littermates who received vehicle alone. These results suggest that mammalian target of rapamycin inhibitors may be effective agents against leukemia and that one of the growth signals inhibited by this class of drugs in precursor B leukemic cells may be IL-7-mediated.

Apc+/Min colonic epithelial cells express TNF receptors and ICAM-1 when they are co-cultured with large intestine intra-epithelial lymphocytes

Adenomatous polyposis coli (APC) functions are involved in the heterotypic interactions occurring between intestinal epithelial cells (IECs) and intra-epithelial lymphocytes (IELs). These interactions may be of interest in cancer prevention, since recent data provide evidence for lymphocyte mediated immunosurveillance of epithelial cancers. The present study attempts to determine if APC inactivation induces changes in the cross-talk between IEC and large intestine IEL (LI-IEL) through intercellular adhesion molecule (ICAM-1)/leukocyte function-associated (LFA-1) interactions. Mouse Apc+/+ and Apc+/Min colonocytes were co-cultivated with LI-IEL. When co-cultured with LI-IEL Apc+/Min IEC but not Apc+/+ IEC expressed high levels of ICAM-1. The presence of ICAM-1 was linked to TNFalpha production in both co-cultures and TNFR expression only in co-cultivated Apc+/Min IEC. Finally, butyrate enhanced the expression of ICAM-1 in Apc+/Min IEC co-cultured with LI-IEL, and the secretion of TNFalpha by both types of co-cultures. These events could participate in determining the Apc+/Min IEC immunogenicity under different in vivo conditions.

Monitoring immune responses in cancer patients receiving tumor vaccines

Clinical evaluation of therapeutic tumor vaccines has resulted in examination and comparison of the types of immune function assays required to monitor tumor antigen-stimulated T cell effector function in immunized patients. Three of the most commonly used assays include ELISPOT, tetramer assay, and cytokine flow cytometry (CFC). Discussed are the method and principles for each assay and an assessment of important methodological, reagent, and data acquisition issues that are relevant for the accurate and effective use of the assays. The sensitivity and utility of the assays and present arguments advocating their integrated use in future immunomonitoring studies are also discussed.