The gut-associated lymphoid system: nature and properties of the large dividing cells

Memory and distribution of virus-specific cytotoxic T lymphocytes (CTLs) and CTL precursors after rotavirus infection

The gastrointestinal tract is constantly exposed to a variety of potentially invasive bacteria, viruses, and parasites. The first line of defense against these pathogens is the intestinal mucosal surface, which consists of epithelial cells, intraepithelial lymphocytes (IELs), mucus, and secretory immunoglobulins. In addition, the intestine is a rich source of lymphocytes located within Peyer's patches and the lamina propria. Little is known about the function, memory, trafficking, or origin of intestinal T lymphocytes after intestinal infection. We studied the murine cytotoxic T-lymphocyte (CTL) response to the intestinal pathogen rotavirus (simian strain RRV). Adult mice were inoculated orally or via the hind footpad with RRV; virus-specific cytotoxic activities in intestinal and nonintestinal lymphocyte populations were determined by 51Cr release assays. In addition, virus-specific CTL precursor (CTLp) frequencies were determined by limiting-dilution analysis. IELs containing rotavirus-specific cytotoxic activity were detected after oral but not footpad inoculation and expressed alpha/beta but not gamma/delta cell surface protein; virus-specific CTLs did not appear to arise from CTLp among IELs. In addition, the site at which RRV was presented to the immune system determined the site at which RRV-specific CTLp first appeared. Frequencies of rotavirus-specific CTLp detected in Peyer's patches were 25- to 30-fold greater after oral than after footpad inoculation. However, regardless of the route of inoculation, rotavirus-specific CTLp were distributed throughout the lymphoid system 21 days after infection. Implications of these findings for vaccine design are discussed.

Two gut intraepithelial CD8+ lymphocyte populations with different T cell receptors: a role for the gut epithelium in T cell differentiation

Mouse gut intraepithelial lymphocytes (IEL) consist mainly (90%) of two populations of CD8+ T cells. One bears heterodimeric alpha/beta CD8 chains (Lyt-2+, Lyt-3+), a T cell receptor (TCR) made of alpha/beta chains, and is Thy-1+; it represents the progeny of T blasts elicited in Peyer's patches by antigenic stimulation. The other bears homodimeric alpha/alpha CD8+ chains, contains no beta chain mRNA, and is mostly Thy-1- and TCR-gamma/delta + or -alpha/beta +; it is thymo-independent and does not require antigenic stimulation, as shown by its presence: (a) in nude and scid mice; (b) in irradiated and thymectomized mice repopulated by T-depleted bone marrow cells bearing an identifiable marker; (c) in thymectomized mice treated by injections of monoclonal anti-CD8 antibody, which lead to total depletion of peripheral CD8+ T lymphocytes; and (d) in germ-free mice and in suckling mice. In young nude mice, alpha/alpha CD8 chains, CD3-TCR complexes, and TCR mRNAs (first gamma/delta) are found on IEL, while they are not detectable on or in peripheral or circulating lymphocytes or bone marrow cells. IEL, in contrast to mature T cells, contain mRNA for the RAG protein, which is required for the rearrangement of TCR and Ig genes. We propose that the gut epithelium (an endoderm derivative, as the thymic epithelium) has an inductive property, attracting progenitors of bone marrow origin, and triggering their TCR rearrangement and alpha/alpha CD8 chains expression, thus giving rise to a T cell population that appears to belong to the same lineage as gamma/delta thymocytes and to recognize an antigenic repertoire different from that of alpha/beta CD8+ IEL.

Mononuclear cells in peripheral venous blood of patients with Crohn's disease: preoperative status and postoperative course, influence of duration, activity and extent of disease

In Crohn's disease (CD) the intestinal lesion is supposed to be the cause of the observed systemic immunologic changes. Based on this assumption, peripheral blood mononuclear cells (PBMC) are of specific interest as a possible indicator of intestinal activity of the disease. From 151 surgical patients CD3+, CD4+, CD8+, B cells, macrophages, leucocytes and the relative number of lymphocytes were analysed preoperatively and 10 days, 3 and 6 months postoperatively. The cell data were correlated with the main clinical data of disease. There was a highly significant preoperative increase of leucocytes, macrophages, CD8+, and B cells in the CD group, and a marked decrease of CD3+, CD4+ cells, and the relative lymphocyte count in the same group. Six months postoperatively, highly elevated macrophages, and leucocytes, and a depressed number of CD4+ cells were the only changes. The preoperative cell data did not correlate with the duration of illness, CDAI, localisation, and extent of the intestinal lesion nor did they correlate with any modality of preoperative drug treatment. Thus, the determination of PBMC characteristics in CD is only of limited value for routine diagnostic purposes. However, the persistence of some pathological values long after operation might be caused by residual microscopic lesions and thus reflect the intestinal process.

A delayed-type hypersensitivity skin-test system using the insulinoma cell line RINm5F to monitor beta cell-specific cellular autoimmune reactivity in the spontaneously diabetic BB/O rat

Islet-specific autoimmune reactivity (humoral and cell-mediated) is the basis for the insulitis process of type I diabetes mellitus. In this report a delayed-type hypersensitivity (DTH) skin test was used to monitor the presence of an islet-specific cell-mediated autoimmune component in BB/O rats. The BB/O rat is a strain characterized by the spontaneous development of type I diabetes. Intact RINm5F cells as well as a RINm5F cell membrane preparation were used as DTH skin test antigens. Rats of different ages and disease stages were tested in the ear with the insulinoma cell line and its cell membrane preparation. As control antigens, the fibroblast cell line 3Y1 and a cell membrane preparation made thereof were used. The DTH reaction system showed a positive cell-mediated reactivity in BB/O rats for membrane-bound RINm5F cell antigens, and not for the control fibroblast 3Y1 cell membrane determinants. The true DTH character of the skin test was established by the time-course of the reaction (maximum at 24 h), the histopathology (infiltration by dendritic cells, lymphocytes and macrophages), and the possibility to transfer the reaction with spleen cells and lymph node cells. The DTH test towards RINm5F cells showed the highest prevalence of positivity (100%) in BB/O rats around the onset of diabetes (3 weeks before to 3 weeks after the onset of glucosuria). The prevalence of DTH positivity was 56% in the period of more than 3 weeks before the onset of glucosuria. In BB/O rats with a duration of glucosuria of more than 3 weeks, the prevalence of positivity was around 60-70%.

Localization of gamma/delta T cells to the intestinal epithelium is independent of normal microbial colonization

Using monoclonal antibodies identifying all gamma/delta and alpha/beta T cell receptors in cytofluorometric analysis, we have compared the composition of intestinal intraepithelial lymphocytes (i-IEL) in euthymic and athymic germ-free (GF) and conventional (SPF) mice. The results show a marked influence of microbial colonization in the numbers of single-positive (CD4+ or CD8+) alpha/beta i-IEL, but little effect in the pool size or characteristics of gamma/delta i-IEL. In young athymic mice, virtually no alpha/beta i-IEL are detected, while considerable numbers of gamma/delta i-IEL remain, though reduced in GF animals.

Lympho-epithelial interactions in the turtle Chrysemys scrypta elegans

The morphological relationships present in the areas of lymphoid infiltration found in the esophagus in Chrysemys scripta elegans were studied by the use of light and transmission electron microscopy. These infiltrations are widespread and can be observed in the lamina propria and the covering epithelium. Electron microscopy reveals the presence of epithelial cells with differing characteristics at the apex of the lymphoid infiltrations. The introduction of horseradish peroxidase (HRP) into the esophageal lumen revealed that these cells possess a micropinocytotic activity. On the basis of the morphological and experimental results obtained, a hypothesis is advanced of the existence, also in the turtle, of a local system of uptake of extraneous material, which induces local and systemic immunological processes.

A diminished adherence of blood lymphocytes of patients with thyroid autoimmune disease to high endothelial venules in the thyroid and the thyroid-draining lymph nodes

The function of high endothelial venules (HEVs), present in the T-cell area of lymphoid tissue is to attract lymphocytes to secondary lymphoid organs ("homing"). In Graves' disease, sporadic goitre and lymphocytic thyroiditis HEVs develop in the thyroid. To study the "homing" of peripheral blood lymphocytes (PBL) of healthy individuals and thyroid patients to the thyroid area we studied the adherence of PBL of such individuals to HEVs present in Hashimoto's goitres and to HEVs in thyroid draining lymph nodes. A modification of the in vitro "homing assay" described by Stamper and Woodruff (J Exp Med 144: 823) was used. The number of PBL of patients with Graves' disease which adhered to thyroidal and thyroid-draining lymphnode HEVs was significantly (p less than or equal to 0.001, Wilcoxon test) less than that of healthy control PBL's; in the case of thyroid HEVs 12 (mean, sd 8, n = 18) patient lymphocytes adhered to 35 HEVs vs 19 (mean, sd 7, n = 16) healthy control lymphocytes; in the case of thyroid lymphnode HEVs 20 (mean, sd 12, n = 15) patient lymphocytes adhered vs 35 (mean, sd 9, n = 9) healthy control lymphocytes. PBL of a few sporadic goitre (n = 5) and atrophic lymphocytic thyroiditis (n = 2) patients also showed a diminished adherence to thyroidal HEVs. We also studied the homing capability of lymphocyte suspensions isolated from the thyroid glands of three Graves' disease patients; these infiltrated cells showed a normal adherence pattern to thyroidal HEVs. We favour the idea that the data should be explained by a redistribution of lymphocytes possessing "thyroid-specific-homing-receptors" from the circulation to the thyroid area in patients with thyroid autoimmune disease.

Lymphocyte homing

The phenomenon of "homing" is discussed with respect to patterns of lymphocyte circulation and the molecules on the surface of both endothelium and lymphocytes that mediate this process. In addition, the data are analysed in the context of a model for lymphocyte homing.

Mechanisms of human lymphocyte migration and their role in the pathogenesis of disease

Lymphocyte recirculation is an essential component of the functional immune system, providing a means for constant surveillance of the organism's tissues by immunocompetent cells and, moreover, facilitating interactions between different cell types engaged in the immune response. Adhesive interactions between recirculating lymphocytes and the wall of high endothelial venules (HEV) are thought to play a central role in this process. These interactions are mediated by lymphocyte homing receptors expressed on the lymphocyte cell surface which recognize tissue-specific molecules on the endothelium. Moreover, LFA-1 is also involved in the regulation of lymphocyte traffic. In addition, recent evidence indicating that these mechanisms may also play a role in the pathogenesis of chronic inflammatory diseases and non-Hodgkin's lymphomas is discussed.

Immunohistologic and functional characterization of a vascular addressin involved in lymphocyte homing into peripheral lymph nodes

The tissue localization or "homing" of circulating lymphocytes is directed in part by specialized vessels that define sites of lymphocyte exit from the blood. In peripheral lymph nodes, mucosal lymphoid tissues (Peyer's patches and appendix), and sites of chronic inflammation, for example, lymphocytes leave the blood by adhering to and migrating between those endothelial cells lining postcapillary high endothelial venules (HEV). Functional analyses of lymphocyte interactions with HEV have shown the lymphocytes can discriminate between HEV in different tissues, indicating that HEV express tissue-specific determinants or address signals for lymphocyte recognition. We recently described such a tissue-specific "vascular addressin" that is selectively expressed by endothelial cells supporting lymphocyte extravasation into mucosal tissues and that appears to be required for mucosa-specific lymphocyte homing (Streeter, P. R., E. L. Berg, B. N. Rouse, R. F. Bargatze, and E. C. Butcher. 1988. Nature (Lond.). 331:41-46). Here we document the existence and tissue-specific distribution of a distinct HEV differentiation antigen. Defined by monoclonal antibody MECA-79, this antigen is expressed at high levels on the lumenal surface and in the cytoplasm of HEV in peripheral lymph nodes. By contrast, although MECA-79 stains many HEV in the mucosal Peyer's patches, expression in most cases is restricted to the perivascular or ablumenal aspect of these venules. In the small intestine lamina propria, a mucosa-associated site that supports the extravasation of lymphocytes, venules do not stain with MECA-79. Finally, we demonstrate that MECA-79 blocks binding of both normal lymphocytes and a peripheral lymph node-specific lymphoma to peripheral lymph node HEV in vitro and that it also inhibits normal lymphocyte homing to peripheral lymph nodes in vivo without significantly influencing lymphocyte interactions with Peyer's patch HEV in vitro or in vivo. Thus, MECA-79 defines a novel vascular addressin involved in directing lymphocyte homing to peripheral lymph nodes.

Effect of the gastrointestinal microflora on induction and maintenance of oral tolerance to ovalbumin in C3H/HeJ mice

The effect of the digestive microflora on oral tolerance to ovalbumin was studied by using axenic (germfree) and conventional C3H/HeJ mice. In contrast to reported results of studies with sheep erythrocytes, oral administration of ovalbumin induced tolerance in axenic mice, but the maintenance of tolerance was found to be of shorter duration than was with conventional mice. These data indicate that the contribution of the microflora to oral tolerance depends on the antigen used.

Ontogenic development of gut-associated lymphoid tissue in the rat. An immunohistochemical study

The development of gut-associated lymphoid tissue (GALT) in the rat was investigated, with special reference to the behavior and ultrastructure of Ia(+) cells during the development of Peyer's patches (PP). At birth, Ia(+) cells were randomly scattered in the lamina propria. From three days, small aggregates of CD4(+), Ia(+), CD5(-) and IL-1(+) cells were observed in the lamina propria. Immunoelectron microscopically, these appeared as mixed populations of dendritic cells, capillary endothelial cells, fibroblast-like spindle cells and lymphocytes. In addition, CD8(+), CD4(-) and IL-1(-) cells were present in the interepithelial space. By seven days, lymphoid follicles were recognizable in the lamina propria, each with an aggregate of IgM-positive small lymphocytes at its center, surrounded by CD4(+) or CD8(+) lymphocytes. Between the 10th and 14th days, these follicles were covered with single-layered, specially differentiated epithelial cells, and structures resembling PP were formed. IgA plasma cells were identified in the lamina propria between the third and the fourth weeks. We speculate that the PP developed from aggregates of Ia(+), IL-1(+) spindle- or dendritic-shaped cells in the lamina propria. The PP were structurally complete by two weeks, although establishment of the characteristic distribution of GALT components evident in the adult took more than six weeks.

The effect of single dose, intravenous cyclophosphamide on the mouse intestinal IgA response to cholera toxin

The IgA response of gut associated lymphoid tissue (GALT) to enteric pathogens is a vital component of the mucosal barrier. This study describes the effect of cyclophosphamide (Cy) on the IgA anti-CT response of Peyer's patch (PP) and lamina propria cells derived from mice previously challenged enterically with two weekly doses of 10 micrograms CT. Under normal circumstances, both PP and lamina propria responses peaked 7 days after the second dose of CT. To evaluate the effect of a single dose of Cy on this response, mice were given Cy (50 mg/kg) intravenously on days -2, 0, 2 or 7 relative to the initial dose of CT. Cultures of PP and jejunal segments were established 7 days after the booster dose of CT (time or normal peak response). A single dose of Cy suppressed the IgA anti-CT response of PP and, to a lesser extent, jejunal segment cultures only if the drug was given 2 days before the primary dose of CT. This suppression of the anti-CT response was overcome when Cy was given 2 days before CT priming, and CT was administered three times, on days 0, 7 and 14; thus, the effect of Cy was brief and did not appear to promote tolerance to CT. These data show that a single, moderate dose of Cy, given before enteric priming of the GALT, can inhibit the mucosal IgA response to CT. The effect of Cy is relatively brief and dependent upon the time at which the drug is given relative to the induction of the mucosal immune response.

Selective recognition of mucosal lymphoid high endothelium by gut intraepithelial leukocytes

Circulating precursors of mucosal immunoglobulin A plasma cells and T-cell immunoblasts migrate selectively into mucosal sites from the blood, but the mechanisms controlling this selective trafficking have not been determined. One possibility is that the site-specific extravasation of circulating effector cell populations is determined by organ-specific endothelial cell recognition mechanisms. Here we have assessed the ability of isolated mouse gut intraepithelial lymphocytes to recognize and bind to mucosal versus nonmucosal lymphoid organ high endothelial venules, vessels that support high levels of lymphocyte traffic in vivo. In an in vitro assay of lymphocyte interaction with high endothelial venules in frozen sections, intraepithelial leukocytes bind well to high endothelial venules in Peyer's patches but, unlike most circulating B and T lymphocytes, are unable to interact with peripheral lymph node high endothelial venules. Furthermore, we show by in situ immunohistology and in cell suspension immunofluorescence studies that intraepithelial leukocytes fail to stain with a monoclonal antibody, MEL-14, against putative lymphocyte receptors for lymph node high endothelial venules. Thus, they lack a cell surface glycoprotein required for homing to peripheral nodes. The demonstration of organ-specific recognition of endothelial cells by a normal mucosal effector lymphocyte population suggests that selective interactions with endothelium may play an important role in controlling the distribution of effector cells in vivo. The utilization of organ-specific endothelial cell recognition mechanisms by circulating precursors of mucosal effector cells could explain both the unification of immune responses in diverse mucosal sites and the physiologic segregation of mucosal from nonmucosal immune mechanisms.

Role of epidermal Langerhans cells in viral infections

Langerhans cells function as highly potent antigen-presenting cells in the epidermis. In the last few years, their role in viral infections has been studied in various experimental systems. They have been shown to be involved in the pathogenesis of a number of infections of viral origin. These include vaccinia virus, human papilloma virus, herpes simplex virus, foot and mouth disease virus and human retrovirus infections. Studies on the effect of various factors, that are known to modulate the activity and density of Langerhans cell in the epidermis, may lead in the future to the development of new strategies aimed at inhibiting virus infections or even eradicating latent infection.

A tissue-specific endothelial cell molecule involved in lymphocyte homing

An endothelial cell surface molecule that is selectively expressed in mucosal organs is required for lymphocyte homing to mucosal lymphoid tissues. This 'vascular addressin' appears to function as a tissue-specific marker or address signal for recognition by lymphocytes circulating in the blood.

Homing receptors and metastasis

As discussed in the preceding sections, there are several indications that the lymphocyte homing receptors involved in the normal process of lymphocyte recirculation are also relevant to the behavior of metastatic cells. Cell fusion experiments indicate that previously nonmetastatic cells can acquire metastatic capacity from fusion with normal lymphocytes. Murine T lymphomas that bear high levels of functional homing receptors can metastasize to peripheral lymphoid organs, whereas those lymphomas lacking homing receptors cannot. Virtually all lymph node metastases of lymphomas contain a high proportion of MEL-14hi cells, even if the primary tumor has been selected to be relatively deficient in these cells. Further investigations of the biology of lymphocyte homing receptors will reveal whether or not there are additional lymphocyte homing receptors and will clarify the role of lymphocyte homing receptors in metastasis. Antibodies against three lymphocyte homing receptors could therefore be useful for diagnosis and treatment of metastatic disease.

Ring-like distribution of IgG-containing cells around the lymph follicle in the human intestine

Immunoglobulin (Ig)-containing cells were studied in the lamina propria of the normal human large bowel and around the lymph follicle, including Peyer's patches, in the normal intestine. Ig-containing cells were identified by the indirect immunoperoxidase staining method, using mouse anti-human Ig monoclonal antibodies. In the lamina propria in the large bowel, the mean percentage of IgA+ (IgA1+ cells and IgA2+ cells), IgM+, IgD+, IgG+ and IgE+ cells was 75.9, 8.5, 7.3, 5.8, 2.5, respectively (total 100), namely there was a marked preponderance of IgA+ cells in comparison to IgG+ cells. However, IgG+ cells were observed not only on the epithelial but also in the serosal side of lymph follicles, showing a ring-like pattern. Ig+ cells of the other four classes did not show such a pattern. The ring-like distribution of IgG+ cells around lymph follicles was observed in both the large and small intestine including Peyer's patches. This tendency was observed in 9 out of 14 follicles (64.3 per cent). A large number of IgG+ cells were observed outside lymph follicles, while a small number of IgG+ cells were observed at the most outer rim of lymph follicles which suggested a local maturation of IgG+ cells. The significance and the role of the newly recognized IgG+ cells in the vicinity of lymph follicles remain to be resolved.

Molecular forms of IgA produced by various lymphoid tissues--analysis using high speed liquid chromatography

Molecular forms of immunoglobulin A (IgA) produced by cultured cells from various human lymphoid tissues were analyzed using high speed liquid chromatography (HLC). IgA secreted into culture media was easily separated into polymeric and monomeric forms by HLC. HLC has the advantages of high resolution, reproducibility, rapidity and technical simplicity in the separation of polymeric and monomeric IgA. Peripheral blood lymphocytes and cells from gut-associated lymphoid tissues, such as mesenteric lymph nodes or large bowel mucosa, secreted predominantly polymeric IgA, whereas lymphoid cells from bone marrow produced mainly monomeric IgA. Spleen cells and tonsillar cells produced nearly equal proportions of polymeric and monomeric IgA. These results suggest that with regard to IgA in serum, the polymer may originate from the gut-associated lymphoid tissues and the monomer may mostly derive from the bone marrow.

An alternative to the magic bullet paradigm for specific cancer therapy

To improve on current cancer therapies, which attack cells on the basis of their proliferative tendencies, much effort has been devoted to a search for properties of tumor cells that are tumor-specific rather than proliferation specific. Evidence from molecular genetic studies suggests, however, that most tumors may lack such properties. An alternative approach to therapy is described that is based on a property known to characterize the majority of human tumors; viz., a monoclonal origin. The strategy requires the prophylactic induction in tissues of mosaicism for genes dictating sensitivity or resistance to chemotherapeutic agents, and exploits the observation that any clone of cells arising in a mosaic tissue must inevitably differ from some other cells in the mosaic. Recent advances in genetic technology imply that the strategy is likely to be testable soon in animals, and that it may significantly improve the results of cancer therapy when a technology safe and efficient enough for its human implementation becomes available.

A monoclonal antibody (HML-1) defining a novel membrane molecule present on human intestinal lymphocytes

A monoclonal antibody, HML-1, was produced by fusion of NSI myeloma cells with spleen cells of a mouse immunized with isolated human intestinal intraepithelial lymphocytes (IEL). Immunofluorescence studies of isolated cells, as well as immunoperoxidase staining of tissue sections, indicated that HML-1 labeled all the various subsets of human intestinal IEL, approximately 40% of lamina propria T cells, 30% mesenteric lymphoblasts and some lymphocytes in other mucosae, particularly IEL. Conversely, it revealed only rare cells in all other lymphoid compartments. Analysis by polyacrylamide gel gradient electrophoresis showed that HML-1 precipitated two major noncovalently bound components of approximate mol. masses of 105 and 150 kDa from human IEL. HML-1 thus defines a novel human membrane antigen present on a subpopulation of lymphocytes preferentially associated with epithelia, and particularly with the intestinal epithelium. The characteristics of this human antigen are very similar to those of an antigen we had previously described in the rat. The possible functional role of this novel class of lymphocyte membrane antigens as well as the nature of the mechanism that triggers their expression remain to be elucidated.

Age-dependent changes of the mesenteric lymph node of Fischer F344 rats: morphological and histometric analysis

Changes in mesenteric lymph nodes from Fischer F344 rats ranging from 5 to 37 months were studied by histological and histometric techniques. The most drastic histological changes were observed between 12 and 37 months of age. These changes include: loss of cellularity in the cortex; decrease in the number of germinal centers; distension of the medullary sinuses; decrease in the ratio of cortical area to medullary area; and infiltration of fibroblastic cells in the cortex and the medulla. Our results indicate a general structural disorganization in the mesenteric lymph node with increasing age. Such structural disturbance might be an important extrinsic factor for the decline in lymphocyte functions.

Immunology of gastrointestinal lymphoma

Experimental work showing that IgA plasma cell precursors activated in gut associated lymphoid tissue (GALT) of rats and sheep migrate to the lamina propria of the gut via the regional lymphatics, mesenteric lymph node and blood, has been supported by immunohistochemical studies. In rats, immunoblasts with cytoplasmic IgA are present in the Peyer's patches in association with the high endothelial venules which is probably an important, though not the only, site of extravasation into the gut, whereas cells with cytoplasmic IgA are rarely observed in the dome regions of Peyer's patches. Immunohistochemical studies of human Peyer's patches have revealed differences between the distribution of cells with cytoplasmic IgA in man compared to rats. In man, immunoblasts with cytoplasmic IgA are not concentrated in the zone of cells containing the high endothelial venules, whereas they are present in the dome regions of the Peyer's patches. The following questions arise: Do precursors of IgA plasma cells activated in human GALT migrate to the lamina propria via the blood, but extravasate predominantly via the capillary network, rather than the high endothelial venules? or do IgA plasma cell precursors 'mature' in situ in the Peyer's patches of man and subsequently migrate laterally to seed the lamina propria? Three lines of evidence from studies of primary B cell lymphomas of GALT support the latter hypothesis: 1) Primary B cell lymphomas of the gut remain localized to GALT for long periods of time; 2) Histological studies of the lymphoid tissue in these lymphomas have shown a gradation of cell types, from the muscularis mucosae towards the mucosal epithelium, which strongly suggests that plasma cells develop in situ in the gut from the adjacent layers of cells; 3) Preliminary studies of DNA extracted from the blood-borne cells from patients with GALT-derived B cell lymphoma have failed to demonstrate the presence of clonal gene rearrangements. Normal and malignant human GALT contains a perifollicular population of B cells with centrocyte-like morphology which lack surface IgD. No direct equivalent can be detected in rodent Peyer's patches. Their quiescent nature and distribution in malignant GALT suggests that they are follicle centre cell-derived and precursors of immunoblasts and plasma cells. As such they may be memory B cells. Their association with epithelium is a consistent feature of normal and malignant GALT which is of unknown but undoubted significance. The function of intraepithelial T cells is still unknown. Malignant T cells in MHI may be derived from intraepithelial T cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Gut-associated lymphoid tissue as source of an IgA immune response in respiratory tissues after oral immunization and intrabronchial challenge

Most IgA plasma cells in the digestive tract are thought to derive from gut-associated lymphoid tissue, whereas IgA plasma cells in the respiratory mucosa are thought to originate largely in bronchus-associated lymphoid tissue. However, previous work has also shown that IgA antibodies to gut antigens can be detected in immunocytes of the bronchial mucosa and in bronchial secretions after appropriate stimulation via the gut. To analyze the cellular origin of such respiratory antibodies, mice were orally immunized with ferritin for 40 days and then segregated for intrabronchial challenge as follows: one group was given saline, another group Formalin-fixed Escherichia coli as a nonspecific challenge, and a third group ferritin. Lungs and intestines from these animals were then examined by immunofluorescence for the presence of plasma cells containing particular isotypes of antibody to ferritin. Animals fed ferritin and given saline or E. coli intrabronchially showed a greater than 6-fold increment in IgA antiferritin plasma cells in the bronchial mucosa, compared to animals which had not received ferritin, whereas orally immunized animals challenged intrabronchially with ferritin showed a greater than 15-fold increase. In other experiments, ferritin-naive animals transfused with mesenteric node cells that were obtained from donors that had been orally immunized with ferritin and were already committed to IgA production showed a 4-fold or greater increase in IgA antiferritin plasma cells in respiratory mucosa after intrabronchial challenge with ferritin when compared to recipients of peripheral node cells from the same donors or to recipients of mesenteric node cells that had not been specifically boosted intrabronchially. These results suggest that immunologically specific IgA immunocytes from gut-associated lymphoid tissue can migrate to the respiratory mucosa after oral immunization, and that migration and/or local cell division are enhanced by subsequent intrabronchial challenge. In providing further evidence for interrelations between gut-associated and bronchus-associated lymphoid tissue, the findings lend added support to the overall concept of a generalized secretory immune system.

Effect of oral vs. parenteral cyclophosphamide on in vitro IgA and IgG production by murine Peyer's patches and cultured jejunal fragments

The gut associated lymphoid tissue plays an important role in intestinal defenses, food allergy, oral tolerance, and certain intestinal diseases. This study describes the effect of either oral or parenteral cyclophosphamide on IgA and IgG production in the gut. Mice were treated with cyclophosphamide either IV or PO, and Peyer's patch cell cultures were established to evaluate mitogen induced production of IgA and IgG. To evaluate the effect of cyclophosphamide on the plasma cell rich lamina propria, segments of jejunum were cultured and overnight secretion of IgG and IgA were measured. We found, the secretion of IgA or IgG by jejunal fragments was not influenced by cyclophosphamide (IV or PO). Mitogen induced secretion of IgA and IgG by Peyer's patch cells was markedly decreased 24 hrs after drug administration, with significant recovery by day 7. Cell mixing experiments revealed that a single dose cyclophosphamide reduced the capacity of Peyer's patch B cells to secrete IgA or IgG when co cultured with normal T cells. This study demonstrates that a single dose cyclophosphamide can have profound effects on the gut immune system and that the drug has a similar effect when given either orally or parenterally.

Comparison of immunoglobulin heavy chain isotype expression in Peyer's patch and splenic B-cells

Past work has shown that B lymphocytes from Peyer's patches (PP) and from spleen differ from each other in the following ways: (1) PP are enriched for IgA-producing precursor cells while splenic B-cells are a rich source of IgM-precursor cells; and (2) PP are a poor source of antibody-secreting cells when compared to the spleen. The reasons for these differences are unclear. In this work B-cells have been examined expressing newly regenerated surface immunoglobulin heavy chains in murine PP and spleens for immunoglobulin isotype expression. Dual color immunofluorescence demonstrated higher levels of B-cells regenerating two surface isotypes in the PP (IgM+ IgG+ = 14.9%; IgM+ IgA+ = 9.4%) than in the spleen (IgM+ IgG+ = 0.4%; IgM+ IgA+ = 0.2%). Poly A+ RNA was purified from these B-cells and compared for immunoglobulin heavy chain isotype expression by DNA-excess slot blot hybridization. Splenic B-cells contained higher amounts (at least two-fold) of Ig heavy chain-specific mRNA per microgram of polysomal RNA than did PP B-cells. Peyer's patches B-cells demonstrated slightly lower mu:alpha ratios than splenic B-cells. In vitro translation of the RNAs suggested higher levels of translatable alpha-specific Poly A+ RNA in PP B-cells than in B-cells from MLN or spleen; furthermore, splenic B-cell RNA contained higher levels of translatable mu-RNA than did the other tissues examined. Northern blot analysis of RNA derived from these tissues identified major mu-, gamma 2b-, and alpha-hybridizing sequences, though PP-derived B-cell preparations were shown to be enriched for the membrane forms of mRNA for gamma 2b and alpha when compared to the spleen-derived B-cell preparations. These results suggest that the level of differentiation of PP B-cells (that are capable of regeneration of surface Ig) may differ significantly from that of splenic B-cells.

Gut injury in mouse graft-versus-host reaction. Study of its occurrence and mechanisms

The occurrence, nature, and pathogenesis of intestinal lesions were studied in a number of graft vs. host reaction (GVHR) conditions in mice, combining variations in the nature of the following: the F1 hosts (newborn or adult, normal or lethally irradiated), the injected parental T cells (mixed or selected subsets of Lyt2+ or L3T4+ cells), and the antigenic stimulus (semi-allogeneic or restricted to class I or II MHC loci). The following conclusions were drawn: Three gut alterations are always associated: donor T cell infiltration, predominating in the crypt region; acceleration of the epithelium renewal; and increased epithelial Ia expression. The initial event is T-cell infiltration, which results from stimulation within the Peyer patches followed by cyclic traffic, i.e., migration into the thoracic duct and then seeding to the whole gut mucosa. Both Lyt2+ and L3T4+ cells can infiltrate the gut wall, the extent of the infiltration by a given subset depending upon the capacity of the donor blasts to circulate in the thoracic duct (higher for L3T4+) and then to home in the gut (much higher for Lyt2+ blasts) and the nature of the alloantigenic stimulation that governs the extent of each donor subset proliferation. Both donor T-cell subsets can induce gut epithelial damage, but for a comparable amount of infiltrating cells, L3T4+ cells induce more lesions. When the antigenic stimulation is restricted to class I or class I MHC loci, gut GVHR is much more easily elicited across class II MHC differences, which stimulate preferentially L3T4+ donor cells. The main mechanism of epithelial damage is not direct cytotoxicity, but more probably lymphokine(s) release.

Unique characteristics of local responses in host resistance to mucosal parasitic infections

Because of the tremendous impact that parasitic infections have on the health and productivity of humans and domestic animals, considerable research effort has been focused upon understanding the mechanisms of host-parasite coexistence, host resistance and immunopathology. Studies have employed a range of approaches including: kinetic analysis of parasite establishment, development, fecundity and survival in naive and previously-infected hosts; correlation between parasite survival and histopathologic responses at the site of infection; vaccination with attenuated parasites or their products; cellular and serum transfer of immunity to naive or immunocompromised hosts; pharmacologic manipulation of potential mediators of host defense using agonistic and antagonistic drugs. However, it is becoming increasingly clear that to understand the mechanisms associated with host resistance and parasite survival, one must define the characteristics of the local microenvironment at the host-parasite interface. One of the approaches by which such studies can be made involves the isolation and characterization of cells derived from the local infection site. This manuscript reviews some of these studies on local aspects of mucosal immune responses in parasitic infections. Examples that will be discussed include IgA antibody, intraepithelial leukocytes from the intestine, intestinal mast cell populations, macrophages derived from bronchoalveolar lavage, and local immunoregulatory responses during respiratory and intestinal parasitic infection. These studies have established unequivocally that local responses to mucosal parasitic infection can only be appropriately investigated using cells derived from the specific microenvironment. This conclusion should encourage others to further study these local responses and to be innovative in investigating unexplored aspects of the host-parasite interface.

Regulation by the skin of lymphoid cell recirculation and localization properties

The existence of epidermal Langerhans cells, Ia-positive dermal dendritic cells, lymphocytes which can demonstrate epidermitropism, and keratinocytes capable of secreting Interleukin-1-like molecules, each support the concept that skin can function as an immunologic organ. Such conclusions are further strengthened by the knowledge that both afferent and efferent immune responses can take place exclusively within the skin. The purpose of our study was to evaluate the ability of skin to regulate lymphoid cell recirculation and localization properties. The use of ultraviolet radiation as an exogenous stimulus resulted in a pronounced redistribution of antigen-presenting cells from central (spleen) to peripheral (skin and lymph node) lymphoid tissues as well as marked increase in the rate of lymphocyte entry into skin draining lymph nodes. This latter condition was due to elevations in the quantitative levels of high endothelial venules present within the peripheral lymph nodes. The ability of epidermal keratinocytes to express Class II molecules is known to be associated with a number of skin diseases. However, the functional significance of this phenomenon is unknown. The results of our studies, employing a nude mouse model, indicate that the expression of Class II molecules by keratinocytes facilitates the movement of Langerhans cell precursors into the epidermis and may also function to enhance lymphocyte entry into the skin. We conclude that nonlymphoid components resident within the skin can influence essential aspects of the adaptive immune response through the production of soluble factors (e.g., Interleukin-1 or through the cellular expression of Class II molecules.

Immunoglobulin-producing cells in lymphatic tissues of germfree and conventional rabbits as detected by an immunofluorescence method

Lymphatic tissues of GF and CV rabbits were observed. No cells producing IgA and IgM antibodies were detected in appendix, sacculus rotundus, ileum terminale and thymus of GF rabbits. IgA cells were found in lymph nodes of GF rabbits.

Diffuse lymphomatous polyposis of the gastrointestinal tract. A case report with immunohistochemical studies

A case of diffuse lymphomatous polyposis of the gastrointestinal tract is reported. The patient presented with abdominal pain and weight loss and x-rays revealed multiple polyps involving the entire gastrointestinal tract. Biopsies confirmed the diagnosis of lymphomatous polyposis. The patient also had involvement of the bone marrow and supraclavicular lymph node. Immunologically this lymphoma was characterized as a monoclonal proliferation of B lymphocytes bearing immunoglobulin M, type kappa. Diffuse lymphomatous polyposis of the gastrointestinal tract appears to be a generalized malignancy of uncommitted B cells of Peyer's patches. The migratory properties of these cells may account for the tendency to dissemination of lymphomatous polyposis. Diffuse lymphomatous polyposis of the gastrointestinal tract is a distinct entity, separate from the diffuse gastrointestinal lymphoma known as Mediterranean-type lymphoma.

Differences of immunoglobulin secreting cells in bone marrow from those in circulation: relevance to their development

The surface markers of immunoglobulin secreting cells (ISC) in bone marrow and peripheral blood were analysed. Circulating ISC bear surface Ig and Ia-like antigens. However, these markers were not detectable on ISC in bone marrow. Fc and complement receptors were not present on circulating ISC. The areas of plaques corresponding to Ig secretion by bone marrow cells were always larger than those of peripheral blood cells. Although the majority of ISC were typical plasma cells, plasmacytoid lymphocytes were observed in peripheral blood. These findings seem to indicate that ISC in the peripheral blood are less advanced in their differentiation and maturation pathway from B lymphocytes to plasma cells than those in bone marrow. ISC in mesenteric lymph nodes exhibited nearly the same phenotype as peripheral cells.

Functional and structural aspects of the epithelial lymphocyte, with implications for coeliac disease and tropical sprue

Epithelial lymphocytes comprise a compartmentalised and specialised population of presumed effector cells which, in general, express the surface phenotypes (Lyt-2+; OX2+; OKT8+) of suppressor/cytolytic (Ts/c) cells. Granular cells within this population (gEL) morphologically resemble the circulating large granular lymphocytes (LGL) which subserve spontaneous (NK) cytolytic activity. Recent in vitro results indicate that gEL can develop this function after prolonged in vitro culture; the relevance of this, in vivo, remains to be decided. EL also appear to be able to mediate ADCC with sIgA against enteric micro-organisms. This is the kind of integrated activity that might be anticipated from local immunocytes within the intestinal mucosa. Other recent work suggests that gEL are not precursors of mucosal mast cells. EL also appear to be capable of inducing Ia-like expression in surface and crypt enterocytes, a property enjoyed both by highly purified Th, but also Ts/c, cells as well. This raises the interesting prospect that enterocytes may display antigen in macrophage-like fashion to other adjacent cells within the inter-epithelial cell spaces. These latter observations might be more consistent with the presence of 'activated' and 'blast-transformed' lymphocytes in such conditions as coeliac disease and tropical sprue. Another emergent view that demands appropriate attention is that the infiltrate of Ts/c cells into surface, and crypt, epithelium of coeliac mucosa does not necessarily cause injury or damage to the jejunal tissues. Nevertheless the role, either primary or secondary, that EL play either in coeliac disease or tropical sprue still remains obscure.