Studies of intestinal lymphoid tissue. I. Electron microscopic evidence of 'blast transformation' in epithelial lymphocytes of mouse small intestinal mucosa

Human intraepithelial lymphocytes

The location of intraepithelial lymphocytes (IEL) between epithelial cells, their effector memory, cytolytic and inflammatory phenotype positions them to kill infected epithelial cells and protect the intestine against pathogens. Human TCRαβ+CD8αβ+ IEL have the dual capacity to recognize modified self via natural killer (NK) receptors (autoreactivity) as well as foreign antigen via the T cell receptor (TCR), which is accomplished in mouse by two cell subsets, the naturally occurring TCRαβ+CD8αα+ and adaptively induced TCRαβ+CD8αβ+ IEL subsets, respectively. The private/oligoclonal nature of the TCR repertoire of both human and mouse IEL suggests local environmental factors dictate the specificity of IEL responses. The line between sensing of foreign antigens and autoreactivity is blurred for IEL in celiac disease, where recognition of stress ligands by induced activating NK receptors in conjunction with inflammatory signals such as IL-15 can result in low-affinity TCR/non-cognate antigen and NK receptor/stress ligand interactions triggering destruction of intestinal epithelial cells.

Porosity of the epithelial basement membrane as an indicator of macrophage-enterocyte interaction in the intestinal mucosa

The epithelial basement membrane of intestinal villi is perforated with numerous small pores, through which free cells in the lamina propria communicate with the enterocytes. This study was a comparative analysis of the pores in the basement membrane by SEM after removal of the gut epithelium with OsO4 maceration. The porosity as represented by the area fraction of the pores varied along the baso-apical axis of villi in patterns specific for each animal species examined: consistent scantiness along the entire length of villi in mice, acute elevation in the second and third distal one-sixths of villi in rats, and gradual augmentation toward the villus tips in guinea pigs. Size distribution analyses of the pores indicated their heterogeneous enlargement in the regions of elevated porosity. Concomitant observation of lamina propria macrophages by histochemical labelings and by conventional TEM showed that the cells specifically clustered beneath the hyperporous basement membrane, with their thick processes penetrating it. The spatially-regulated patterns of perforation of the epithelial basement membrane indicate phase-specific interventions of lamina propria macrophages in the maturation or aging of enterocytes, which steadily proliferate in crypts and exfoliate at the villus tips.

Lamina propria T cell subsets in the small and large intestine of euthymic and athymic mice

We investigated lamina propria T cells from the small intestine (jejunum/ileum) and the large intestine (colon) of euthymic (BALB/c, C.B-17, C57BL/6) and athymic (C57BL/6 nu/nu; BNX bg/bg nu/nu xid/xid) mice. CD3+ T cells represented about 40% of the lamina propria lymphocytes (LPL) from the small or the large intestine of euthymic mice, and 20-30% of the LPL populations from the small or large intestine of athymic mice. In the lamina propria T cell population of the small intestine, 85% were of the alpha beta lineage in euthymic mice, but only 40% were of the alpha beta lineage in athymic mice. T cells of the gamma delta lineage were thus more frequent than T cells of the alpha beta lineage in the intestinal lamina propria T cells of extrathymic origin. CD4+ T cells represented 40% of the lamina propria T cells in the small as well as in the large intestine of euthymic mice, and 20-30% of the T cells in the lamina propria of the nude mouse gut. In euthymic mice, 40% of the T cells in the small intestine lamina propria, and 30% of the T cells in the colonic lamina propria were CD8+. In intestinal lamina propria T cell populations of athymic mice, the CD8+ T cell population was expanded. Most (60-70%) CD8+ T cells in the lamina propria of the small and the large intestine of euthymic and athymic mice expressed the homodimeric CD8 alpha + beta- form of the CD8 coreceptor. A fraction of 15-20% of all CD3+ T cells in the lamina propria of the small and the large intestine of euthymic and athymic mice were 'double negative' CD4- CD8-. A large fraction of the TCR alpha beta + T cells in the colonic lamina propria (but not in the small intestine lamina propria) of euthymic mice expressed the CD2 and the CD28 costimulator molecules, the adhesion molecule LECAM-1 (CD62 L), and could be activated in vitro by CD3 ligation. These data reveal a considerable heterogeneity in the surface phenotype and the functional phenotype of murine lamina propria T cells.

Changes in the intestinal lymphoid compartment throughout life: implications for the local generation of intestinal T cells

The intestinal lymphoid compartment has a rather stable composition throughout life. However, both during early neonatal development and at high age unique cell populations can be recognized at distinct sites in the intestinal tissue. Directly after birth all intestinal CD3+ cells are found in the lamina propria. At this time the epithelium does not contain T cells. These CD3+ lamina propria lymphocytes co-express both TCR beta and TCR delta chains, probably reflecting the expression of a TCR beta delta heterodimer on the cell surface. Cells with this particular phenotype are present in comparable numbers in the lamina propria of both neonatal euthymic and athymic mice, indicating the thymus-independent nature of these cells. During aging the frequency of TCR alpha beta+ CD8 alpha alpha+ intestinal T cells increases. These cells are also considered to be thymus-independent. The appearance of high numbers of CD4+ CD8 alpha alpha+ intestinal T cells in aged mice is even more striking. It is postulated that the neonatal TCR beta delta+ cells, and probably also the CD4+ CD8 alpha alpha+ cells as found in old mice, are intermediates in the extrathymic differentiation pathway of TCR alpha beta+ CD8 alpha alpha+ intestinal T cells.

The biology and pathobiology of the intestinal intraepithelial lymphocyte: a review of the literature

Intraepithelial lymphocytes represent a population of lymphocytes situated in the epithelial layer of all mucosae. In this report their biological and pathobiological features, with emphasis on intestinal intraepithelial lymphocytes, are reviewed.

Functional properties of intra-epithelial lymphocytes from mouse small intestine. IV. Investigation of the proliferative capacity of IEL using phorbol ester and calcium ionophore

Intra-epithelial lymphocytes (IEL) from mouse small intestine normally show very poor proliferative responses to mitogens or antigens in vitro. In this report, we show that purified IEL give a moderate proliferative response when stimulated with a combination of phorbol myristate acetate (PMA) and the calcium ionophore, A23187. Nevertheless, the response of IEL to these agents was much less than that of other lymphoid cells, even when stimulated additionally with concanavalin A (Con A). Furthermore, in comparison with spleen cells, the optimal response of IEL to PMA required higher concentrations of A23187. Optimally stimulated IEL made significant amounts of T-cell growth factor and addition of rIL-2 to the cultures did not enhance the optimal response of IEL to PMA + A23187. Subsequent studies showed that the majority of IEL which respond to PMA + A23187 are L3T4+ Lyt-2-, despite the fact that Lyt-2+ cells from the spleen and thymus responded well to these agents. Our study indicates that the majority of IEL have a very low proliferative potential in vitro and this may reflect a large population of IL-2-unresponsive Lyt-2+ IEL.

Lymphoepithelial interactions in the mucosal immune system

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Studies of intestinal lymphoid tissue. X-observations on granular epithelial lymphocytes (gEL) in normal and diseased human jejunum

A proportion of epithelial lymphocytes in various mammalian species is characterised by cells containing cytoplasmic granules. We have studied the total number of granular lymphocytes within surface and crypt epithelium of jejunal mucosae (per 10(4) micron2 muscularis mucosae) from six groups of subjects, comprising (i) young healthy volunteers (ii) family relatives of known coeliac patients, patients with gastrointestinal disorders associated with either (iii) normal or (iv) "flat" mucosae, and groups of (v) untreated and (vi) treated patients with coeliac disease. There was no difference in the absolute number of gEL between the three control groups with normal mucosal architecture, the proportion of granular to total EL per unit of tissue varying between 30-40%. In untreated coeliac mucosae, there was a significantly increased population of gEL, compared with the same control groups (p less than 0.001): the ratio of granular to total EL approximated 65%, and did not differ from flat-control mucosae in which the proportion of gEL was 55%. On withdrawal of gluten, the absolute number of gEL fell significantly in comparison with the untreated coeliac group (p less than 0.05). To further evaluate the effect of gluten challenge, granular lymphocytes were monitored during a five-day period in groups of treated coeliac patients orally challenged with increasing doses (500-3000 mg) of a peptic-tryptic digest of gluten. A significant rise in the absolute number of granular lymphocytes occurred at 12 h, but without any deterioration in mucosal architecture.

Lymphocyte migration into the lamina propria of the gut is mediated by specialized HEV-like blood vessels

Migration of lymphocytes into the lamina propria of the small intestines was studied in mice using short-term in vivo migration experiments in combination with immunocytochemistry and autoradiography. The results show that, shortly after intravenous injection, most of the lymphocytes present in the lamina propria are actually located within the capillary network of the villi. Furthermore, it was shown that lymphocytes leave the blood stream and enter the lamina propria via small blood vessels at the base of the villi. These blood vessels can be discriminated by their positive staining with MECA-325, a monoclonal antibody that is specific for high endothelial venules (HEV) in lymphoid organs. From the results it is concluded that the gut contains specialized venules at specific sites, involved in the emigration of lymphocytes, comparable to HEV in lymphoid organs. The flatness of the endothelium of these MECA-325-positive intestinal blood vessels, which is in contrast to the situation in lymphoid organs, could not be changed by inducing an intestinal inflammation. This flatness may be directly correlated to the less efficient transmigration of lymphocytes, as demonstrated in our experiments.

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)

Frequency of occurrence and distribution of the intra-epithelial lymphoid cells in the follicle-associated epithelium in phenotypically normal and athymic nude mice

We have determined the number and pattern of spatial distribution of intraepithelial lymphoid cells in the follicle-associated epithelium of Peyer's patches and in the villus epithelium in the small intestine of athymic nu/nu mice and of the phenotypically normal mice kept in specified pathogen-free conditions. The results were obtained by histometric analysis of semithin histological sections. It has been found that the lymphoid cells were scattered randomly in the villus epithelium, while those in the follicle-associated epithelium were non-randomly distributed, occurring often in groups of several cells both for athymic nu/nu and phenotypically normal mice. The numbers of lymphoid cells in the follicle-associated and in the villus epithelium were found to be significantly lower in athymic nu/nu mice than in phenotypically normal mice kept in similar conditions. On the basis of the above results the proportions of thymus-dependent and thymus-independent lymphoid cells in the intestinal epithelium were deduced.

Morphometric and cytochemical analysis of lysosomes in rat Peyer's patch follicle epithelium: their reduction in volume fraction and acid phosphatase content in M cells compared to adjacent enterocytes

M cells are specialized epithelial cells over lymphoid follicles in Peyer's patches which take up viruses, bacteria, and antigenic macromolecules from the intestinal lumen. Unlike ordinary enterocytes which sequester pinocytosed material in lysosomes, M cells transport such material across the epithelium to antigen-processing areas in lymphoid follicle domes, suggesting a difference in lysosomal activity or a different route for movement of endocytic vesicles. Ileal Peyer's patches in rats were examined by electron microscopy to identify lysosomes by acid phosphatase activity. Acid phosphatase was found in dense bodies in enterocytes but not in M cells. Stereological analysis showed the volume fraction occupied by dense bodies in M cells to be 16 times less than in enterocytes (P less than .0005), even though the volume fractions of cytoplasm occupied by mitochondria in M cells and enterocytes were not significantly different. The small volume fraction of dense bodies and the absence of acid phosphatase activity in M cells thus correlate with absence of lysosomal degradation of luminal microorganisms during transport into lymphoid follicles by M cells and may provide not only a complete array of microbial antigens for initiation of immune responses, but also a route through the mucosal barrier for microorganisms which can evade local containment mechanisms.

Functional characterization of Con A-responsive Lyt2-positive mouse small intestinal intraepithelial lymphocytes

The surface phenotypes of resting vs Con A-stimulated intraepithelial lymphocytes (IEL) from mouse small intestine were directly determined by immunofluorescence with double labelling. Both Thy 1.2+, Lyt 2+ and Thy 1.2+ Lyt 2- IEL underwent blastogenesis and expressed interleukin-2 (IL-2) receptors. The Lyt 2+ subsets of IEL (which represent 80% of the total cells) were isolated by panning and shown to proliferate in response to Con A and IL-2, although the frequency of responsive precursors was dramatically lower than that seen in the splenic Lyt 2+ T-cell population (1 in 500 vs 1 in 8, respectively). Con A-stimulated Lyt 2+ IEL produced lymphokines supporting the growth of the interleukin-3 (IL-3)-dependent cell line DA-1, and of the FDC-P2 cell line that proliferates in response to both IL-3 and GM-CSF. The results therefore support the possibility that Lyt 2+ IEL act as inducers of local cell-mediated immune reactions by producing haematopoietic lymphokines.

Morphology and functional characteristics of isolated porcine intraepithelial lymphocytes

We have examined the morphology and functional characteristics of porcine intraepithelial lymphocytes (IEL). A subpopulation of IEL contains granules as seen in other species, and their ultrastructure was also similar. They were capable of producing T-cell growth factor and interferon on in vitro stimulation. IEL killed P815 cells in the presence of PHA, but did not kill K562 cells.

Mesenteric lymphoblast localization throughout the murine small intestine: temporal analysis relating intestinal length and lymphoblast division

Mesenteric lymphoblasts (MLN) have a predilection to selectively localize in the lamina propria and epithelium of the small intestine. Using an adoptive transfer method, we examined the localization kinetics of these blasts in the intestinal wall with respect to their distribution from duodenum to terminal ileum and also assessed their mitotic activity by autoradiographic techniques. 3H-thymidine-labelled MLN cells were found throughout the small intestine by 6 hr post-transfer and reached a maximum frequency in this organ by 24 hr post-transfer. Donor blasts were most frequent in the duodenum and terminal ileum regions of the gut. Subsequently, the frequency of labelled cells throughout the intestinal wall declined to near zero. The apparent accumulation of MLN blasts in the gut was not related to either a temporary retention and departure from the pulmonary vasculature or to mitotic division of labelled cells in the gut wall. A model describing the relationship between MLN blast localization kinetics in various segments of the intestine was formulated.

Pit cells in extrahepatic organs of the rat

Electron microscopic examination of the extrahepatic distribution of pit cells, a cell type found in the liver, revealed their existence in several other organs of the rat. They were relatively frequent in lungs, spleen (red pulp), small intestine, epididymis, trachea, and peripheral blood; much fewer in bone marrow and thymus (medulla); and nonexistent in lymph nodes, spleen (white pulp), and thymus (cortex). The pit cells in these organs, as well as in the liver, contained characteristic dense granules and rod-cored vesicles in the cytoplasm. Our observations suggest that pit cells circulating in the peripheral blood adhere to the endothelium of capillaries in the various organs and migrate into the tissue, where they have some special immunological function.

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.

Fenestrations of the basal lamina of intestinal villi of the rat. Scanning and transmission electron microscopy

Fenestrations of the basal lamina of rat intestinal villi were revealed by scanning electron microscopy after removal of the overlying epithelial cells by osmic acid maceration. These fenestrations are circular to oval in shape and are 0.5 micron to 5 microns in diameter. They are richly distributed at a density of 1-2 X 10(4)/mm2 in the upper two thirds of the villi, except at the very tips. Roughly 500 fenestrations are found on each side of an average sized tongue-shaped villus. Transmission electron-microscopic observations showed that these fenestrations were passages for migrating cells of the immune system such as lymphocytes, eosinophils and macrophages. Protrusions from the basal parts of epithelial cells were also observed passing through these fenestrations. These findings are discussed with respect to their immunological implications and to the passage of nutrients.

Studies of intestinal lymphoid tissue. VII. The secondary nature of lymphoid cell "activation" in the jejunal lesion of tropical sprue

Morphometric techniques were used in the evaluation of lymphocyte morphology and activity in tropical sprue. jejunal biopsies from control subjects (8), patients with epidemic disease (7), patients with endemic disease (11), and subjects who had recovered from sprue (4) were analyzed blindly. In patients with sprue, lymphocytes were increased significantly within crypt (but not surface) epithelium. Immunoblasts (greater than 6 mu in diameter) were increased by 5% over control subjects. Group means for lymphocytic mitotic indexes were also significantly raised, while flux ratios only differed significantly between endemic sprue patients and control subjects. The lymphocytic infiltration was distributed focally in the upper crypt and crypt-villus interzones. Analysis of epidemic cases (presenting within 4-28 days) revealed detectable changes in lymphocyte behavior only after 3 weeks' illness, whereas mucosal lesions and malabsorption were already established during the first week. These data indicate that lymphocyte activation, suggestive of a local cell-mediated immune reaction, does occur in tropical sprue but is secondary to damage already inflicted on enterocytes and their function.

Distribution and morphological characteristics of the pit cells in the liver of the rat

Pit cells, on which almost no further contributions have been presented since the first report by Wisse et al. (1976), are described in detail in the rat liver. These cells show several characteristic features: 1) "rod-cored vesicles", a new type of vesicular inclusion observed first in our study; 2) electron-dense granules, which we consider to arise from multivesicular bodies by the accumulation of dense material; and 3) well-developed pseudopodia. Although these features clearly differentiate pit cells from conventional lymphocytes, these two cell types display similarities (i) in a number of ultrastructural features, (ii) in the pattern of their intralobular distribution, and (iii) in their presence in the spleen and peripheral blood.

Studies of intestinal lymphoid tissue. VI--Proliferative response of small intestinal epithelial lymphocytes distinguishes gluten- from non-gluten-induced enteropathy

Several diseases of the small intestine, including gluten-sensitivity, present with malabsorption and a "flat" mucosa. Determination of the mitotic index of epithelial lymphocytes provides a simple, objective method of assessing, and thus of predicting, whether a flat mucosa is due to gluten-sensitivity (index greater than 0.2%), or not (index less than 0.2%). The use of this index in circumstances especially likely to cause diagnostic confusion--for example, intestinal lymphoma; Crohn's jejunitis of immunodeficiency--is illustrated in this paper. Of seven cases, five (two primary lymphoma, three immunodeficiency) had been treated with a gluten-free diet without benefit; a mitotic index performed on the initial biopsy in each of these patients could have predicted from the outset that none was gluten-sensitive. Of the remaining two cases, determination of the mitotic index on the biopsy initially obtained from a man with severe hypogammaglobulinaemia would have indicated that he was also gluten-sensitive. Empirical use of a gluten-free diet was avoided in the other patient (with flat small intestinal mucosa and low mitotic index) in whom the diagnosis was ultimately shown to be due to Crohn's disease of jejunum.

Studies of intestinal lymphoid tissue. IV--The predictive value of raised mitotic indices among jejunal epithelial lymphocytes in the diagnosis of gluten-sensitive enteropathy

It has been established that considerable blast-transformation and mitotic activity occurs among epithelial lymphocytes of untreated coeliac mucosa. This paper is concerned solely with the proliferative activity of epithelial lymphocytes (expressed as percentage "mitotic index") in the prospective diagnosis of coeliac disease, in comparison with other conditions such as lymphoma. Crohn's disease and immunodeficiency which are often associated with malabsorption and flattening of jejunal mucosa. The results demonstrate that a high mitotic index (greater than 0.2%) clearly distinguishes, and hence predicts, gluten-associated enteropathies (including dermatitis herpetiformis and malignant histiocytosis) from others in which gluten plays no aetiological role and where the mitotic index differs insignificantly from normal control mucosae (much less than 0.2%). Furthermore, it has been demonstrated that the mitotic index is raised in so-called "non-responsive coeliacs," thus suggesting that such patients may also be gluten-sensitive despite their subsequent failure to respond morphologically to dietary gluten restriction.

Intraepithelial leukocytes of the intestinal mucosa in normal man and in Whipple's disease: a light- and electron-microscopic study

Intraepithelial lymphocytes (IEL) of the intestinal mucosa of normal man and of patients with Whipple's disease were studied by light microscopy of 1-micron-thick sections, and by electron microscopy of thin sections. IEL in normal human intestine tend to be elongated in outline, have few cytoplasmic organelles, have compact nuclei, and are unattached to epithelial cells. IEL in Whipple's disease are more likely to be activated in appearance, ie, to be larger and to contain more cytoplasmic organelles than IEL of normal intestine. The number of IEL/100 intestinal epithelial cells is similar in normal man and in patients with Whipple's disease. Other intraepithelial (IE) cells found in normal intestine include eosinophils and mast cells, and we note for the first time the presence of IE macrophages. There are no "globule leukocytes" in the intestine of normal man or of patients with Whipple's disease. Other IE cells found in the intestine in Whipple's disease include eosinophils, polymorphonuclear (PMN) leukocytes, and macrophages in untreated disease and intraepithelial macrophages in treated disease. These IE cells may be involved in the acute and chronic immune responses of the intestine.

Relation between HLA-DR-like antigens and secretory component (SC) in jejunal epithelium of patients with coeliac disease or dermatitis herpetiformis

HLA-DR-like antigens and secretory component (SC) were localized immunohistochemically in adjacent tissue sections of ethanol-fixed paraffin-embedded jejunal mucosa from control subjects and patients with coeliac disease (CD) or dermatitis herpetiformis (DH). HLA-DR-like antigens were found in a patchy distribution apically in the columnar epithelial cells facing the gut lumen and in the upper part of the crypt epithelium. The staining pattern was similar in controls and patients with CD or DH. SC was normally most abundant in the crypt epithelium but the concentration of SC in the surface epithelium increased with increasing villous atrophy both in CD and DH patients. Despite this sign of immaturity, the surface cells retained their capacity to express HLA-DR-like antigens in the pathological mucosa.

Immunohistochemical identification of T- and B-lymphocytes delineated by the unlabelled antibody enzyme method. III. Topographical and quantitative distribution of T- and B-cells in human palatine tonsils

T-lymphocytes and B-lymphocytes are identified in tissue sections of human tonsils by applying the unlabelled antibody enzyme method. The epithelium of the tonsils contains a majority of immunoglobulin-positive cells and fewer T-lymphocytes. In the subepithelial zones, areas composed of B-cells predominate, however, regions containing T-lymphocytes are also present. The latter are mainly arranged in the lamina propria around high-endothelial venules and often include plasma cells containing immunoglobulin. Follicles containing germinal centres display a complex structure which changes during development. The lymphocytic cap consists of densely packed lymphocytes, labelled heavily by anti-IgM and anti-IGD, and of individual T-lymphocytes. Germinal centres show a framework of immunoglobulin-positive dendritic reticular cells; they contain some heavily labelled lymphoid cells and several cells weakly labelled by anti-IgM and anti-IgA, as well as a small number of T-lymphocytes. Furthermore, the total areas of T- and B-lymphocytes measured by planimetry may differ considerably between different tonsils. Especially total areas of germinal centres vary to a great extent. The quantitative data on amounts of T- and B-cells achieved by planimetry are comparable to those reported in cellular suspensions of tonsils.

Mucosal immunology

In this review, we shall highlight some recent advances in mucosal immunology and also those concepts which seem to us to merit more attention than they normally receive. Since we cannot hope to be all inclusive, we recommend the following articles and books to the reader (Tomasi & Bienenstock, 1968; Tomasi & Grey, 1972; Bienenstock, 1974; Heremans, 1974; Mestecky & Lawton, 1974; Lamm, 1976; Tomasi, 1976; Waksman & Ozer, 1976; Porter & Knight, 1977; McGhee, Mestecky & Babb, 1978; Ogra & Dayton, 1979; Befus & Bienenstock, 1980).

Organ culture of adult mouse intestine. I. Morphological results after 24 and 48 hours of culture

Explants of adult mouse intestine have been maintained in organ culture for 24 to 48 hr. The best results have been obtained with a mixture of DMEM-HEPES medium and NCTC-135 enriched with 10% fetal bovine serum. The morphology of the mucosa is well preserved at the light and electron microscopic level: absorbing cells exhibit an increase in secondary lysosomes; goblet cells and Paneth cells remain active; numerous mitoses are observed in the crypts; and vigorous re-epithelization takes place on the margin of the explants.

Morphometric electron and light microscope analysis of lymphoid cells in coeliac disease

Lymphocytes in jejunal biopsies from normal subjects and from untreated, treated, and gluten-challenged coeliac patients were examined by accurate morphometric methods. There was no significant difference between lymphocytes from different sources and those in the jejunum. Transforming lymphocytes were ultrastructurally quite different from non-transforming lymphocytes. The appearance of transforming lymphocytes in the lamina propria in different groups of coeliac patients is in accordance with the increase in the number of plasma cells. In treated patients the results indicate a rapid humoral response to gluten challenge.

The natural history of the cells producing IgA in the gut

The IgA-secreting cells in the lamina propria of the small intestine are derived from large lymphocytes which enter the blood by way of the thoracic duct and then migrate into the gut where they complete their differentiation into plasma cells. Three aspects of this cellular traffic have been examined in rats. 1. The cells in thoracic duct lymph which give rise to IgA-secreting cells in the lamina propria are among those which carry surface IgA. Blast cells lacking surface immunoglobulin migrate mainly into the Peyer's patches and do not contribute to the IgA response. 2. Studies on a secondary antibody response to cholera toxoid, in which the challenge was given into a Thiry-Vella loop, showed that the antibody-containing blast cells in thoracic duct lymph were derived from Peyer's patches. The mesenteric nodes contributed little, if anything, to the cellular response in the lymph. 3. The idea that secretory component is a signal for the emigration of large lymphocytes from the blood into the lamina propria lacks experimental support. Secretory component does not bind to the IgA on the surface of thoracic duct cells. On the other hand, antigen in the gut may play an important part in immobilizing large lymphocytes in the lamina propria once they have migrated.

Identification of T and B lymphocytes in human breast cancer with immunohistochemical techniques

Cryostat sections of 50 breast cancer specimens and several lymphoid organs were investigated with antisera against human T-lymphocyte antigen, human lymphocytes, and human immunoglobulins using the immunofluorescence technique and the immunoperoxidase technique. These methods proved to make it possible to discriminate between T and B cells in lymphocytic infiltrates in tissue sections. In nearly all mammary carcinomas studied, T cells were found to predominate in and around tumor cell nests. Only the intraductal carcinomas of this series contained a substantial number of B cells in addition to T cells. The presence of T cells indicates that the host-tumor interaction in vivo mall-mediated immune reaction. The role of the B cells found in the lymphocytic infiltrates of the intraductal carcinomas is still a matter of speculation. Moreover, these findings enhance the value of established histologic classifications. These classifications may have to be modified to provide them with a more functional basis.

Stimulation of lymphocytes from patients with coeliac disease by a subfraction of gluten

Peripheral-blood lymphocytes from patients with coeliac disease showed a marked increase in D.N.A. synthesis after incubation in vitro with a subfraction of gluten. Lymphocytes from control patients showed no increased D.N.A. synthesis under the same conditions. The possible use of this specific lymphocyte-stimulation assay as a screening test for coeliac disease is discussed.

Evaluation of the intraepithelial lymphocyte count in the jejunum in childhood enteropathies

Intraepithelial lymphocyte counts were evaluated in 131 jejunal mucosal biopsies taken from children with a small intestinal enteropathy arising from a variety of causes including coeliac disease, (untreated, after gluten withdrawal, and during subsequent challenge), giardiasis, cow's milk protein intolerance, and 'intractable diarrhoea'. The counts were compared with those from the biopsies of children referred for investigation but in whom no gastrointestinal disease was demonstrated and from healthy siblings of children with coeliac disease, investigated during a family study. Children with coeliac disease showed a raised count which fell after gluten withdrawal as has been demonstrated by others in adults. Lymphocytic infiltration of the epithelium increased rapidly during gluten challenge in such children, while no change was seen in those children proven ultimately not to have coeliac disease by the usually recognized criteria. In other enteropathies the range of counts was wide, overlapping with both normal and coeliac groups and indicating the nonspecificity of lymphocytic infiltration of the gut epithelium. The findings are discussed in relation to their significance and to further avenues of investigation to determine their possible diagnostic value in confirming the diagnosis of coeliac disease during gluten challenge.

T cell depletion in untreated adult coeliac disease

The proportional and absolute numbers of circulating thymus dependent lymphocytes (T cells) were reduced in untreated patients with coeliac disease but were normal after treatment with a gluten free diet. There was an inverse correlation between circulating T cell numbers and jejunal intraepithelial lymphocytes. This evidence suggests a possible role for T cells in the pathogenesis of coeliac disease and is a further example of disturbed cell mediated immunity in this condition.

Studies of intestinal lymphoid tissue. II. Aspects of proliferation and migration of epithelial lymphocytes in the small intestine of mice

Mice were given either intraperitoneal tritiated thymidine (3H-Tdr) or colchicine to study proliferation and migration of intestinal epithelial lymphocytes. Both labelled medium and large lymphocytes ('immunoblasts') were observed throughout the epithelium, crossing the basement membrane and within villous lymphatics for at least seven days after 3H-Tdr administration. Epithelial lymphocytes are predominantly young cells, actively dividing at the rate of 1% per hour. They do not migrate along the villi, unlike epithelial cells, but circulate rapidly through the epithelium, returning to the lamina propria at the rate of approximately 3 epithelial lymphocytes/1000 epithelial cell nuclei/hour. The labelling pattern of epithelial lymphocytes and intralymphatic cells with time was very similar suggesting that epithelial lymphocytes therefore may directly enter adjacent lymphatics and hence gain access to thoracic duct lymph.