Peyer's Patch Lymphocytes Research Articles

Translocation of Yersinia entrocolitica across reconstituted intestinal epithelial monolayers is triggered by Yersinia invasin binding to beta1 integrins apically expressed on M-like cells.

Yersinia enterocolitica cross the intestinal epithelium via translocation through M cells, which are located in the follicle-associated epithelium (FAE) of Peyer's patches (PP). To investigate the molecular basis of this process, studies were performed using a recently developed in vitro model, in which the enterocyte-like cell line Caco-2 and PP lymphocytes are co-cultured in order to establish FAE-like structures including M cells. Here, we demonstrate that Y. enterocolitica does not adhere significantly to the apical membrane of differentiated enterocyte-like Caco-2 cells that express binding sites for Ulex europaeus agglutinin (UEA)-1. In contrast, Y. enterocolitica adhered to, and was internalized by, cells that lacked UEA-1 binding sites and displayed a disorganized brush border. These cells were considered to be converted to M-like cells. Further analysis revealed that part of these cells expressed beta1 integrins at their apical surface and, as revealed by comparison of wild-type and mutant strains, interacted with invasin of Y. enterocolitica. Consistently, anti-beta1 integrin antibodies significantly inhibited internalization of inv-expressing yersiniae. Experiments with Yersinia mutant strains deficient in YadA or Yop secretion revealed that these virulence factors play a minor role in this process. After internalization, yersiniae were transported within LAMP-1-negative vacuoles to, and released at, the basal surface. Internalization and transport of yersiniae was inhibited by cytochalasin D, suggesting that F-actin assembly is required for this process. These results provide direct evidence that expression of beta1 integrins at the apical surface of M cells enables interaction with the invasin of Y. enterocolitica, and thereby initiates internalization and translocation of bacteria.

Ileal and jejunal Peyer's patches play distinct roles in mucosal immunity of sheep.

The majority of pathogens enter the body through mucosal surfaces and it is now evident that mucosal immunity can provide effective disease protection. However, the induction of mucosal immunity will require efficient targeting of mucosal vaccines to appropriate mucosa-associated lymphoid tissue. An animal model, based upon the surgical preparation of sterile intestinal 'loops' (blind-ended segments of intestine), was developed to evaluate mucosal and systemic immune responses to enteric vaccines in ruminants. The effectiveness of end-to-end intestinal anastomoses was evaluated and fetal surgery did not disrupt normal intestinal function in lambs up to 6-7 months after birth. The immunological competence of Peyer's patches (PP) within the intestinal 'loops' was evaluated with a human adenovirus 5 vector expressing the gD gene of bovine herpesvirus-1. This vaccine vector induced both mucosal and systemic immune responses when injected into intestinal 'loops' of 5-6-week-old lambs. Antibodies to the gD protein were detected in the lumen of intestinal 'loops' and serum and PP lymphocytes proliferated in response to gD protein. The immune competence of ileal and jejunal PP was compared and these analyses confirmed that jejunal PP are an efficient site for the induction of mucosal immune responses. This was confirmed by the presence of gD-specific antibody-secreting cells in jejunal but not ileal PP. Systemic but not mucosal immune responses were detected when the vaccine vector was delivered to the ileal PP. In conclusion, this model provided an effective means to evaluate the immunogenicity of potential oral vaccines and to assess the immunological competence of ileal and jejunal Peyer's patches.

A new isolation method for rat intraepithelial lymphocytes

Intraepithelial lymphocytes (IELs) play critical roles in gut immunity. In mice, γδ T cells are a large component of the IEL population. In the rat, γδ IELs are reportedly much less common, but technical issues suggest that previous analyses should be interpreted cautiously. The study of IELs in rats has been impeded by isolation procedures that are lengthy and complex, leading to small cell yields. For this reason, it is possible that rat IELs analyzed in previous studies have not been representative of the entire IEL compartment. We report a new method for the isolation of rat IELs that is based on the selective removal of intestinal epithelial cells under conditions that leave the basement membrane undisturbed. The method is rapid and requires neither enzymatic digestion, nor surgical removal of Peyer's patches, nor vigorous mechanical manipulation of the intestine. The yield of rat IELs using this method is 5- to 10-fold greater than that reported for other methods. Morphological and phenotypic analyses demonstrated that the purified cell population is comprised of IELs and is not contaminated with lamina propria or Peyer's patch lymphocytes. Phenotypic analysis revealed five major subsets of IELs based on differential cell surface expression of CD4, CD8, and αβ T cell receptor (TcR). Among the αβTcR − cells was a population of γδ T cells present at levels not previously detected. The isolation of IEL sub-populations using this methodology should facilitate studies of the function of these cells in gut immunity.

Evaluation ofin vitro cytotoxicity of tetramethylarsonium hydroxide in marine animals

We have studied the cytotoxicity in vitro of tetramethylarsonium hydroxide (TetMA-OH), which is found in some marine animals, in various murine immune effector cells, including splenocytes, thymocytes, Peyer's patch (PP) lymphocytes, peritoneal macrophages (PMs) alveolar macrophages (AMs) and bone-marrow (BM) cells, using synthetic material which was compared with an inorganic arsenical, sodium arsenite. Arsenite showed strong cytotoxicity in these cells, with an IC50 (the concentration that reduced the number of surviving cells to 50% of that in untreated controls) of about 2–9 µmol dm−3. In contrast, TetMA-OH was less toxic, even at a concentration above 10 mmol dm−3, in these immune effector cells, and no enhancement effect on the viability of the cells was observed. These data suggested that TetMA-OH had no biological effect, either toxic or modulating on any immune effector cells in vitro. Copyright © 1999 John Wiley & Sons, Ltd.

Role of immunoglobulin A monoclonal antibodies against P23 in controlling murine Cryptosporidium parvum infection.

Cryptosporidium parvum is an important diarrhea-causing protozoan parasite of immunocompetent and immunocompromised hosts. Immunoglobulin A (IgA) has been implicated in resistance to mucosal infections with bacteria, viruses, and parasites, but little is known about the role of IgA in the control of C. parvum infection. We assessed the role of IgA during C. parvum infection in neonatal mice. IgA-secreting hybridomas were developed by using Peyer's patch lymphocytes from BALB/c mice which had been orally inoculated with viable C. parvum oocysts. Six monoclonal antibodies (MAbs) were selected for further study based on indirect immunofluorescence assay reactivity with sporozoite and merozoite pellicles and the antigen (Ag) deposited on glass substrate by gliding sporozoites. Each MAb was secreted in dimeric form and recognized a 23-kDa sporozoite Ag in Western immunoblots. The Ag recognized comigrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with P23, a previously defined neutralization-sensitive zoite pellicle Ag. MAbs were evaluated for prophylactic or therapeutic efficacy against C. parvum, singly and in combinations, in neonatal BALB/c mice. A combination of two MAbs given prophylactically prior to and 12 h following oocyst challenge reduced the number of intestinal parasites scored histologically by 21.1% compared to the numbers in mice given an isotype-matched control MAb (P < 0.01). Individual MAbs given therapeutically in nine doses over a 96-h period following oocyst challenge increased efficacy against C. parvum infection. Four MAbs given therapeutically each reduced intestinal infection 34.4 to 42.2% compared to isotype-matched control MAb-treated mice (P < 0.05). One MAb reduced infection 63.3 and 72. 7% in replicate experiments compared to isotype-matched control MAb-treated mice (P < 0.0001). We conclude that IgA MAbs directed to neutralization-sensitive P23 epitopes may have utility in passive immunization against murine C. parvum infection.

T-Helper 1 and T-Helper 2 Cytokine Responses in Gut-Associated Lymphoid Tissue Following Enteric Reovirus Infection

Enteric infection of mice with reovirus serotype 1 elicits antibody and cytotoxic T-lymphocytes in gut-associated lymphoid tissue (GALT). This led to the hypothesis that T-helper 1 (Th1) and T-helper 2 (Th2) responses develop in GALT. Reverse transcriptase–polymerase chain reactions on RNA from Peyer's patches (PP), intraepithelial lymphocytes (IEL), and lamina propria (LP) lymphocytes demonstrated that interferon (IFN)-γ message was increased in PP and IEL, but not in LP following infection. No increase in mRNA for interleukin (IL)-4, IL-5, or IL-6 was detected. IFN-γ, IL-5, and IL-6 were produced inin vitrocultures of PP 4–10 days postinfection. PP and spleen lymphocytes from infected mice produced IFN-γ, but no IL-5 following in vitro restimulation. Infection also induced production of mRNA for the β2 chain of the IL-12 receptor in PP. We conclude that reovirus induces robust Th1 and weak Th2 cell responses in GALT.

Inhibition of murine splenic and mucosal lymphocyte function by enteric bacterial products.

Previously we showed that lysates of enteropathogenic Escherichia coli (EPEC) inhibit lymphokine production by mitogen-activated human peripheral blood and lamina propria mononuclear cells. The aims of the present study were to determine whether EPEC-inhibitory factors have similar effects on murine lymphoid populations in order to further delineate the mechanisms of alteration of cytokine production. Preexposure to EPEC lysates inhibited mitogen-stimulated interleukin-2 (IL-2), IL-4, and gamma interferon (IFN-gamma) production by murine spleen cells, but IL-10 production was increased. The inhibition was not due to increased apoptosis and was not blocked by neutralizating antibodies against IL-10 or transforming growth factor beta (TGF-beta). EPEC lysates also inhibited mitogen-stimulated IL-2 and IFN-gamma production by CD11b-depleted spleen cells, IL-2 and IL-4 production by intraepithelial and Peyer's patch lymphocytes, IL-2 production by the human T-cell line Jurkat, and antigen-stimulated IL-2 production by murine spleen cells. Lysates obtained from Shiga-like toxin-producing E. coli, E. coli RDEC-1, Citrobacter rodentium, and an EPEC espB insertion mutant all inhibited IL-2 and IL-4 production by mitogen-stimulated lymphoid cells. In conclusion, lysates of EPEC and related bacteria directly inhibit cytokine production by lymphoid cells from multiple sites by a mechanism that does not increase apoptosis or result from secondary effects of IL-10 or TGF-beta.

Increased Mucosal B-Lymphocyte Apoptosis During Polymicrobial Sepsis Is a Fas Ligand But Not an Endotoxin-Mediated Process

AbstractSepsis is reported to induce an increase in the rate of apoptosis (Ao), in immature lymphoid cells residing in hematopoietic tissues such as the thymus and bone marrow. Alternatively, secondary lymphoid tissue, such as the spleen exhibit little innate (unstimulated) Ao. However, it is unknown whether or not polymicrobial sepsis has any effects on the frequency of Aoin mucosal lymphoid tissue and what, if any, are the functional consequences of such a change. To assess this, Peyer's patch cells were harvested from C3H/HeN (endotoxin-sensitive) mice killed 12 or 24 hours after the onset of polymicrobial sepsis (cecal ligation and puncture [CLP]). The results indicate that the percentage of cells that were Ao+ as determined by flow cytometry were markedly increased at 24 hours, but not at 12 hours post-CLP. This correlates well with evidence of increased DNA fragmentation as well as histological changes observed both at a light and transmission electron microscopic level of the Peyer's patch Ao. Phenotypically, these changes were restricted to the B220+ (B-cell) population that also exhibited a marked increase of Fas/Apo-1 antigen expression. The functional consequence of this increased apoptosis appears to be associated with the endogenous stimulation (activation) of IgA production by mucosal B lymphocytes and increased nuclear c-Rel expression. Furthermore, we found that Peyer's patch lymphocytes isolated from C3H/HeJ-Faslgld(endotoxin-tolerant/Fas ligand- [FasL] deficient) as opposed to C3H/HeJ (endotoxin-tolerant) inbred mice did not exhibit increased Ao after CLP. These findings indicate that increased B-cell Ao appears to be a FasL-Fas antigen-mediated process, but is not due to endotoxin sensitivity. In conclusion, we speculate that the increased Fas-associated apoptosis detected in mucosal B cells (as opposed to splenic or bone marrow B cells) may be due to increased luminal antigens other than endotoxin, released due to gut barrier integrity breakdown during sepsis.

Expression of major histocompatibility complex class II antigens in the canine intestine

Immunohistochemical techniques were used to assess major histocompatibility complex (MHC) class II expression by enterocytes and lamina propria cells in the canine intestinal tract. Duodenal enterocyte class II expression was faint and limited to the lower crypt region whereas jejunal and ileal enterocyte expression was stronger, being present in both crypt and villus areas. Enterocyte staining was of greatest intensity in crypts adjacent to Peyer's patches and intense membrane staining of most Peyer's patch lymphocytes was also seen. Enterocyte MHC class II expression in the colon was largely limited to the lower crypt region. Within the lamina propria, of all intestinal sites examined, a heterogeneous population of cells were MHC class II positive and these had morphological features of macrophages and dendritic cells. Lymphocytes, plasma cells, fibroblasts and vascular endothelium were not stained. Definition of constitutive expression of MHC class II within the canine intestine may be important in identifying upregulation of this molecule in inflammatory bowel diseases.

A fetal sheep liver extract reverses age-related increments in spontaneous and induced cytokine production by indirect environmental effects

BALB/c, DBA/2 and C57BL/6 mice of different ages (ranging from 8 to 110 weeks of age) were used as spleen cell donors to assay cytokine production from ConA activated spleen and Peyer's Patch (PP) lymphocytes. As reported in an earlier publication, there was an age-related decline in IL-2 production in all strains, with a general increase in IL-4 and IL-10 production with age, this being particularly marked for PP cell preparations. Similar conclusions were reached from independent analysis of CD44 hi and CD44 lo cell populations in these groups (memory vs. naive cells, respectively). Interestingly, IL-6 production was dramatically increased (some 4–5-fold in the different strains) and significantly increased levels of IL-6 were detected in the serum of aged mice. A previously described sheep fetal liver extract was able to reverse, to varying degrees, these cytokine changes associated with aging. Interestingly, when cells from aged mice were adoptively transferred to lethally irradiated young (8 week) recipients, the cytokine production phenotype of cells harvested from recipient mice 3 weeks later was that of the aged donor, unless recipients were treated continually with extract. Treatment of the donor alone produced minima1 changes in cytokine production 3 weeks following adoptive transfer. The effect of extract was reversed in treated aged mice by concomitant daily intravenous infusion of the competitive inhibitor of nitric oxide synthesis (NG-monomethyl- l-arginine (NMMA)), which also decreased the increased serum nitrate levels in mice treated with extract. Our data suggest an important role for reactive nitrogen products, themselves induced by fetal liver extract, in age-associated changes in cytokine production.

In Vivo Anti-Influenza Virus Activity of Kampo (Japanese Herbal) Medicine “Sho-Seiryu-To”—Stimulation of Mucosal Immune System and Effect on Allergic Pulmonary Inflammation Model Mice

When BALB/c mice were treated with a Kampo (Japanese herbal) medicine “Sho-seiryu-to (SST)” (1 g/kg, 10 times) orally from 7 days before to 5 days after the infection and infected with mouse-adapted influenza virus A/PR/8/34 by nasal-site restricted infection, SST caused increment of the influenza virus hemagglutinin-specific IgA antibody secreting cells in nasal lymphocyte but not in Peyer's patch lymphocyte at 6 days after infection in comparison with water-treated mice. Oral administration of SST also augmented IL-2 receptor β chain+ (activated) T-cell in Peyer's patch lymphocyte, but not in the nasal lymphocyte. We previously reported that SST showed potent anti-influenza virus activity through augmentation of the antiviral IgA antibody titer in the nasal and broncho-alveolar cavities of the mice (T. Nagai and H. Yamada, 1994, Int. J. Immunopharmacol. 16, 605–613). These results suggest that oral administration of SST shows anti-influenza virus activity in the nasal cavity by activatation of T-cell in Peyer's patch lymphocyte and stimulation of production of anti-influenza virus IgA antibody in nasal lymphocyte. When ovalbumin-sensitized allergic pulmonary inflammation model mice were administered orally with SST (1 g/kg) from 8 days before (11 times) or from 2 h after (4 times) to 4 days after the infection and infected with mouse-adapted influenza virus A/PR/8/34, replications of the virus in the both nasal and broncho-alveolar cavities or only nasal cavity were significantly inhibited at 5 days after infection in comparison with water-treated control by augmenting antiviral IgA antibody, respectively. These results suggest that SST is useful for both prophylaxis and treatment of influenza virus infection on patients with allergic pulmonary inflammation, such as bronchial asthma.

Summary of workshop findings for antibodies reacting with porcine T-cells and activation antigens: results from the Second International Swine CD Workshop

After initial evaluation of the 176 new and 19 control monoclonal antibodies (mAb) submitted to the Second International Swine CD Workshop, 57 were assigned to the T-cell/activation marker subgroup. These 57 mAb were further analyzed using flow cytometry on whole blood lymphocytes, splenocytes, Peyer's patch lymphocytes, in vitro cell lines, broncho-alveolar lavage cells, Con A and PHA blasts, fetal cell populations, and by 2-color flow cytometry against mAb to porcine CD2, CD4, and CD8. Finally, the molecular weights of the target antigens were characterized when possible. As a result of these analyses, 23 mAb were distributed into 7 CD clusters. Newly confirmed mAb assignments included: two CD2; one CD4; two CD5; one wCD6; and one wCD25. Three new mAb were found that reacted with wCD8, one of which defined a new epitope, wCD8c. For the first time, mAb against porcine CD3 were identified, including 6 mAb that reacted with three different epitopes. Several new mAb reacted with antigens whose expression varied depending on the activation state of the test cell. These will require further characterization in order to assign a CD number.

Conversion by Peyer's patch lymphocytes of human enterocytes into M cells that transport bacteria.

The epithelium that lines the gut is impermeable to macromolecules and microorganisms, except in Peyer's patches (PPs), where the lymphoid follicle-associated epithelium (FAE) contains M cells that transport antigens and microorganisms. A cultured system that reproduces the main characteristics of FAE and M cells was established by cultivation of PP lymphocytes with the differentiated human intestinal cell line Caco-2. Lymphocytes settled into the epithelial monolayer, inducing reorganization of the brush border and a temperature-dependent transport of particles and Vibrio cholerae. This model system could prove useful for intestinal physiology, vaccine research, and drug delivery studies.

Alterations in mouse Peyer's patch lymphocyte phenotype after ethanol consumption

The objective of this study was to determine if chronic ethanol consumption could modify cell populations in the Peyer's patches (PP), which could favor pathogenic or opportunistic infections in mice, as seen in chronic alcohol addicts. Young C57BL/6 mice receiving the Lieber-DeCarli diet (36% of calories as ethanol) for 5 weeks presented a significant decrease in the total number of cells in the PP. Mature FVB mice receiving the Lieber-DeCarli diet for 19 weeks presented a highly significant decrease in the total number of cells and in the absolute number of T and B cells in the PP. Young C57BL/6 mice receiving the 100% NRC (30% ethanol) or the 60% NRC (30% ethanol) diets for 7 weeks presented alterations in the T and B cell phenotype comparable with the alterations observed in mice receiving the Lieber-DeCarli diet for 19 weeks. As less alcohol for a shorter time caused similar changes to those seen with a highly micronutrient enriched diet with more alcohol for a longer consumption period, micronutrient supplementation may overcome some immune damage found in animal models of alcoholism. Our data indicated that ethanol administration altered the mucosal immune system at the level of the PP, the site for antigen presention and induction of a mucosal immune response.

Peyer's patches in murine AIDS: dissociation between lymphoproliferation and anergy.

RadLV-Rs infection induces a murine immunodeficiency syndrome associated with a dramatic enlargement of spleen and lymph nodes. Surprisingly, the lymphoproliferation excludes thymus and Peyer's patches (PP). To understand the cellular interactions underlying lymphoproliferation further, the authors investigated the fate of PP in RadLV-Rs infected mice. The atrophy of PP was mostly due to the depletion of B cells, while the proportion of CD4+ and CD8+ T cells was increased. Nevertheless, B cell phenotype was modified with the emergence of lymphocytes with a low expression of B220 in infected PP. T cells characterized by a memory/activated phenotype in control PP did not undergo phenotypical changes after viral infection (i.e. regarding Thy-1 and CD44 expression). Despite the absence of lymphoproliferation, PP T and B cells displayed altered responses to mitogens in vitro. Finally, alterations of the expression of adhesion molecules and vascular addressins could not explain the atrophy of PP by a reduced homing to this lymphoid site. B cells and T cells from normal PP are clearly different from lymph nodes (LN) lymphocytes. The authors propose that the particular functional state which characterizes PP lymphocytes influences the B cell/T cell crosstalk necessary for RadLV-Rs-induced lymphoproliferation.

Sensitized Liposomes as an Antigen Delivery System for the Stimulation of Mucosal Immunity

This study was designed to exploit the ability of Peyer's patch M cells to recognize antigen-antibody complexes in the targeted delivery of a model antigen for the induction of mucosal immunity. Sensitized liposomes consisted of an entrapped model antigen, ovalbumin (OVA), and coated with unrelated antigen-antibody complexes. Sensitized liposomes were administered intrajejunally to mice either with or without monophosphoryl lipid A (MLA). Humoral immune responses were monitored in saliva, feces, serum, and bile. Mice which received sensitized liposomes showed up to 4-fold amounts of specific IgA in saliva, feces, and bile compared to controls. Transient increases in anti-OVA IgA and IgG were observed in serum. Formulations including MLA generated positive anti-OVA IgG responses in both serum and bile. In separate experiments, cell proliferation studies were performed with Peyer's patch lymphocytes harvested from mice immunized with OVA in either standard or sensitized liposomes. Lymphocytes from test mice receiving only sensitized liposomes proliferated in the presence of OVA, but not an unrelated antigen. Taken together, these results support the potential application of antigen-antibody complexes in the stimulation of mucosal immune responses and that MLA may play an important role in overcoming OVA tolerogenicity.

Apoptosis by CD95 (Fas)-dependent and -independent mechanisms in Peyer's patch lymphocytes in murine retrovirus-induced immunodeficiency syndrome.

CD95 (Fas)/CD95 ligand (CD95 L)-mediated apoptosis is thought to be involved in the delayed progression of murine AIDS (MAIDS) induced by LP-BM5 murine leukemia virus (MuLV). We show evidence of apoptosis in lymphocytes of Peyer's patches (PP) at the early stage of MAIDS. Both T and B cells in PP expressed CD95 at the early stage of MAIDS and decreased in number thereafter. The decrease in T cells was not evident in CD95-mutated lpr mice with MAIDS, suggesting that CD95/CD95 L interaction is involved in the apoptosis of T cells in PP during the course of MAIDS. On the other hand, the number of B cells was also decreased in PP of lpr mice with MAIDS. The proliferative ability of B cells in PP of MAIDS mice in response to immunoglobulin M cross-linking or lipopolysaccharide was severely impaired, while the B cells normally proliferated in response to anti-CD40 monoclonal antibody. These findings imply that aberrantly activated B cells in PP undergo apoptosis independently of the CD95/CD95 L system during the course of infection with MAIDS virus.

Cloning of the mucosal addressin MAdCAM-1 from human brain: identification of novel alternatively spliced transcripts.

The mucosal addressin cell adhesion molecule-1 (MAdCAM-1), expressed selectively on high endothelial venules (HEV) and lamina propria venules, directs lymphocyte traffic by binding the lymphocyte Peyer's patch adhesion molecule-1 (LPAM-1, alpha 4 beta 7). Full-length DNA encoding human MAdCAM-1 was obtained by combining sequences from an expressed sequence tag (EST) identified in an early stage human brain cDNA library, a polymerase chain reaction-derived clone, and a MAdCAM-1 genomic clone. The deduced amino acid sequence revealed an 18 amino acid signal peptide, two N-terminal immunoglobulin (Ig)-like domains conserved (59-65%) in sequence with those of the mouse homologue, an 86 amino acid mucin-like region rich in serine-threonine residues, a 20 amino acid transmembrane domain and a 43 amino acid charged cytoplasmic domain. No counterpart to the third IgA-like domain of mouse MAdCAM-1 was present; however, the serine-threonine-rich mucin domain was extended as two distinguishable major and minor mucin regions unrelated to the mouse domain. The major domain is formed from six tandem repeats of an eight amino acid sequence having the MUC-2-related consensus DTTSPEP/SP. Human MAdCAM-1 mRNA transcripts were restricted to small intestine, colon, spleen, pancreas and brain. Alternatively spliced MAdCAM-1 variants were identified that lack parts of the second Ig domain and all or part of the major mucin domain, indicating that the function of this vascular addressin is regulated by extensive modifications to its multi-domain structure.

Study on adhesion factors in lymphocyte migration to the middle ear mucosa.

We investigated influences of adhesion factors on the migration of antigen-specific IgA-forming cells (ASAFCs) to the middle ear mucosa by means of an in vitro lymphocyte binding assay. Peyer's patch (PP) lymphocytes from guinea pigs with mucosal immunization, which are rich in ASAFCs, more frequently bound with the inflamed middle ear mucosa than those of PP and spleen cells from animals with systemic immunization, in which antigen-specific IgG-forming cells (ASGFCs) were induced (p > .001). The bindings were not affected by antigenic and nonantigenic stimuli to the middle ear mucosa for producing otitis media. On human middle ear mucosa from 10 patients with acute mastoiditis and chronic otitis media, endothelial cells of newly grown vessels were stained strongly with intercellular adhesion molecule (ICAM)-1, and weakly with vascular cell adhesion molecule (VCAM)-1, platelet endothelial cell adhesion molecule (PECAM), and endothelial leukocyte adhesion molecule (ELAM)-1. Many lymphocytes bound mainly to these endothelial cells, and a few cells were observed bound to the basal portion of epithelial cells. The binding of lymphocytes was significantly, but not completely, inhibited by anti-ICAM-1 antibody (p < .001). These findings suggest that PP lymphocytes with activated mucosal immunity more frequently migrate to the inflamed middle ear mucosa, and that those migrations, after extravasation, may be regulated by the interaction between various binding factors and their receptors on lymphocytes, which is different from that of adhesion molecules and their ligands in the extravasation.

β2 Integrins and ICAM-1 Are Involved in Establishment of the Intestinal Mucosal T Cell Compartment

Development of the mucosal immune system was examined in mice with partial loss of expression of ICAM-1 or CD18. Profound effects on Peyer's patch (PP), lamina propria (LP), and intraepithelial lymphocyte (IEL) T cell populations were observed in mu- tant mice. Normal expression of CD18 integrins and ICAM-1 was essential for development of the CD8αβ TCRαβ LP and IEL compartment and for the generation of normal PP lymphocyte populations. The partial loss of CD8αβ IEL correlated with the loss of TCRαβ IEL-mediated lytic activity. The presence of a subset of Thy1 + TCRγδ IEL was also dependent on CD18 integrins and ICAM-1. Both the lytic activity and the expression of CD11c by TCRγδ IEL were up-regulated in the presence of TCRαβ T cells. Analysis of bone marrow chimeras demonstrated that a bone marrow–derived ICAM-1 + accessory cell was involved in the generation of some TCRαβ IEL. These results demonstrated that ICAM-1 and β2 integrins were required for establishment of a normal intestinal immune system.