Studies of intestinal lymphoid tissue. XV. Histopathologic features suggestive of cell-mediated reactivity in jejunal mucosae of patients with dermatitis herpetiformis

An update on celiac disease histopathology and the road ahead

CONTEXT

Celiac disease (CD) is a common immune-mediated disorder that occurs in genetically predisposed individuals (carriers of HLA-DQ2 and DQ8 haplotypes) on consumption of wheat (gluten). It is characterized by inflammation of the small-intestinal mucosa and myriad gastrointestinal and systemic manifestations. Celiac disease is common in the general population (prevalence, 0.5%-1%). Currently, small-bowel biopsy is considered the gold standard for diagnosing CD. However, the role of serologic testing in the diagnosis of CD has evolved, from being a supportive test to supplanting intestinal biopsies in certain patient populations.

OBJECTIVE

To summarize key aspects of histopathologic assessment, discuss the benefit of standardized pathology reports, impact of the site and number of small-bowel biopsy samples on diagnosis, and recommendations regarding serologic testing.

DATA SOURCES

Literature review of publications on CD and experience with histopathologic review of biopsies at the Department of Pathology and Cell Biology, Columbia University Medical Center, New York-Presbyterian Hospital, New York.

CONCLUSIONS

Intraepithelial lymphocytosis in the context of villous atrophy is considered a characteristic histologic finding of CD; however, it is a rather nonspecific finding. A growing list of publications has also indicated that the detection of intraepithelial lymphocytosis in the absence of villous atrophy has rather low specificity for CD. Therefore, communication between pathologists and gastroenterologists is paramount, as is knowledge regarding the pertinent clinical and laboratory data, in distinguishing between CD and other disorders with similar histopathologic and clinical manifestations.

Proximal small-bowel mucosal villous intraepithelial lymphocytes

Small-bowel biopsies are routinely obtained from adult patients as a screening tool to evaluate the possibility of gluten sensitivity (GS). Previous morphological criteria of GS including completely flattened villi are usually absent. In the context of screening for GS, an altered distribution density pattern of villous intraepithelial lymphocytes (IELs) is probably the most sensitive morphological feature to suggest the possibility of GS and prompt the initiation of further medical evaluation. Altered villous IEL density distribution is a more sensitive screening feature than villous IEL counts. With increased small-bowel GS screening biopsies, occasional adults without GS with complete villous flattening and numerous villous IELs are encountered. These patients are usually incorrectly diagnosed with GS. However, they do not respond to a gluten-free diet and slowly improve over months.

Morphologic features suggestive of gluten sensitivity in architecturally normal duodenal biopsy specimens

We studied small bowel biopsy specimens with architecturally normal villi from 78 adult patients with potential gluten sensitivity (GS) and correlated them with outcome to characterize morphologic features that would allow a pathologist to suggest GS. No patient had a previous GS diagnosis. Twelve study patients had GS. The mean number of intraepithelial lymphocytes (IELs) per 20 enterocytes from the tips of 5 random villi was significantly greater in GS than non-GS biopsy samples, but the groups overlapped significantly, making the number diagnostically useful only when markedly increased. Crypt mitoses counts had similar relationships. Twelve patients had an even distribution of IELs along villus sides and over tips (3/66 [5%] non-GS patients, 9/12 [75%] GS patients). Non-GS patients had a decrescendo pattern of IELs along the sides of villi. Architecturally normal small bowel biopsy specimens with an appreciable, continuous, even distribution of IELs along the sides and tips of villi and a mean of 12 or more IELs in the tips of several villi are suggestive of GS. Pathologists should be watchful for these morphologic features in small bowel biopsy specimens to suggest GS.

Histopathology of celiac disease

The diagnosis of celiac disease (CD) is based upon histologic findings in duodenal or jejunal biopsies. In the past few years it has turned out that the development of CD lesion in the small bowel is a dynamic process which may present in various histologic forms. At one end of the spectrum is a mucosa with normal architecture and an increase in intraepithelial lymphocytes (IEL), at the other end is the classical flat mucosa. Histologic features supporting the diagnosis of CD are architectural changes of the villi and/or crypts, an increase in lamina propria cell density and an increase in IEL counts. For diagnostic purposes and for monitoring CD patients an exact histologic classification of the histologic findings has to be given. This has become possible by using a modified Marsh classification. In the present paper the histologic presentation of CD is presented as well as the modified Marsh classification.

Circulating autoantibodies to tissue transglutaminase differentiate patients with dermatitis herpetiformis from those with linear IgA disease

BACKGROUND

Dermatitis herpetiformis (DH) is highly associated with celiac disease. Recently, tissue transglutaminase (tTG) was identified as the autoantigen of IgA antibodies in celiac disease. The prevalence of antibodies to tTG in DH patients is not known.

OBJECTIVE

The purpose of this study was to determine whether DH patients show circulating IgA autoantibodies to tTG, to compare their serum levels with those from patients with other subepidermal autoimmune bullous diseases, and to correlate levels of antibodies to tTG with the extent of small bowel disease.

METHODS

Sera were obtained from consecutive patients with DH (n = 11), linear IgA disease (n = 15), bullous pemphigoid (n = 10), and epidermolysis bullosa acquisita (n = 6) and were studied by indirect immunofluorescence on monkey esophagus and NaCl-split human skin. IgA reactivity to tTG was measured by enzyme-linked immunosorbent assay. The extent of mucosal involvement in jejunal biopsy specimens was assessed according to the grading of Marsh.

RESULTS

All untreated DH patients showed circulating IgA autoantibodies to tTG. One DH patient already undergoing therapy, the 15 patients with linear IgA disease, and all other controls revealed no autoantibodies to tTG. In addition, serum levels of IgA anti-tTG antibodies reflected the degree of histopathologic changes in jejunal mucosa from biopsy specimens in DH patients.

CONCLUSION

Our results show that circulating IgA autoantibodies to tTG are detectable in DH but not in linear IgA disease or other subepidermal autoimmune bullous diseases. The levels of IgA anti-tTG antibodies reflect the extent of histopathologic changes of the jejunal mucosa in DH.

New clinical issues in celiac disease

Celiac disease is a chronic disorder of gluten sensitivity associated with a spectrum of mucosal lesions termed preinfiltrative, infiltrative, hyperplastic, destructive, and atrophic. The symptoms are not related to the degree of mucosal pathology but to the extent of the mucosal lesion. Neoplasms constitute the major complication of celiac disease, and EATCL is the most common neoplasm in this category. There is evidence that a strict gluten-free diet is protective against the complications of celiac disease; hence it is important that even the subclinical forms be diagnosed early. Small bowel biopsy remains the gold standard for diagnosis of celiac disease; however, antibody tests are a useful adjunct in deciding whom to biopsy and for screening groups at high risk before initiating a lifelong gluten-free diet.

Morphology of the mucosal lesion in gluten sensitivity

Gluten sensitivity is associated with a spectrum of mucosal lesions, arbitrarily termed pre-infiltrative, infiltrative-hyperplastic, flat-destructive and atrophic-hypoplastic. Histologically and immunohistologically these lesions are all compatible with T-cell-driven events operative at a local mucosal level. They are classifiable either in terms of antibody titres (pre-infiltrative) (see Chapter 10) or by the characteristic disposition of IELs throughout the surface and crypt epithelium. From in-vivo challenges, it has been demonstrated: (i) that all these lesions comprise a dynamically interrelated series of events, culminating in the severe flat-destructive lesion; and (ii) that gluten evokes a dose-responsive infiltration of IELs (CD3+ CD8+ and TCR alpha beta + or gamma delta +) into the epithelium. Apart from that, little is known of the functions of IELs; it is possible they may have little to do with the evolving mucosal pathology of gluten sensitivity. Increasing work seems to support a view, proposed from this laboratory over 10 years ago, that the immune-mediated responses in jejunal tissue in gluten sensitivity arise in the lamina propria, in association with DR+ macrophages and an abundance of CD4(+)-activated lymphocytes. Many other inflammatory consequences flow from these interactions, involving activation of mast cells, eosinophils and neutrophils, elaboration of cytokines and other products of inflammation, and increased hyperpermeability of the microvasculature with upregulation of adhesion molecules. The result is a doubling of lamina propria volumes in the severe flat lesion. Evidence is also given to show that measurable changes in lamina propria inflammation occur with the infiltrative-hyperplastic lesion. Symptomatology is not related to the degree of proximal mucosal pathology, but to the extent of the mucosal lesion. Data, although scanty, suggests that lesional pathology involves only 30-50% of the entire small bowel mucosa. Thus, most patients, irrespective of proximal mucosal damage, have latent (or asymptomatic) gluten sensitivity. Symptom development requires additional environmental triggers, of which infection is a major contributor. It should also be noted that, while these various environmental triggers may precipitate symptomatology, they do not advance the severity of the mucosal lesion.

Gamma/delta T-cell receptor expression in the jejunal epithelium of patients with dermatitis herpetiformis and coeliac disease

The density of jejunal intra-epithelial T cells expressing the gamma/delta form of the T-cell receptor is known to be increased in coeliac disease, the significance of which remains a mystery. The expression of the gamma/delta T-cell receptor in the jejunum of patients with dermatitis herpetiformis, coeliac disease, treated and untreated, and controls were studied. Expression of the gamma/delta T-cell receptor was significantly increased in patients with dermatitis hepetiformis (P < 0.0005) and in both untreated (P < 0.0005) and treated coeliac patients (P < 0.05) compared with controls. There were significant correlations between the indices of enteropathy, enterocyte height (P < 0.005) and villous height/crypt depth ratio (P < 0.0001), and expression of the gamma/delta T-cell receptor in the jejunum of all the patients. This argues against the hypothesis that gamma/delta T-cells have a fundamental role in the aetiology of gluten-sensitive enteropathy. It suggests that gamma/delta T cells may be involved in the effector arm of the mucosal immune response to cereal peptides in susceptible individuals.

Intestinal antibody pattern of celiac disease: occurrence in patients with normal jejunal biopsy histology

BACKGROUND

Patients with celiac disease have immunoglobulin (Ig) M antibodies and IgA antigliadin antibody in gut secretions; this pattern of intestinal immunity may be a marker of latent celiac disease. Its frequency in patients referred for jejunal biopsy has been examined.

METHODS

Serum IgG and IgA antigliadin antibody, jejunal fluid IgA and IgM antibodies to gliadin, ovalbumin and beta lactoglobulin, and jejunal fluid IgA and IgM concentrations were measured by enzyme-linked immunosorbent assay.

RESULTS

Seventeen of 19 celiac patients on normal diet and 16 of 23 on gluten-free diet had the celiaclike antibody pattern, as did 41 of 217 other patients. Jejunal biopsy histology had been classified as normal in 38 of these, with minor abnormalities in 3; however, intraepithelial lymphocyte (IEL) counts were high in 13 cases. Trial of a gluten-free diet produced clinical improvement in 6 of 7 antibody-positive patients. After extra dietary gluten, one developed subtotal villous atrophy.

CONCLUSIONS

The celiaclike intestinal antibody pattern and a high IEL count may be markers of latent gluten-sensitive enteropathy; some of these patients are clinically gluten sensitive in the absence of enteropathy.

The interactive role of mucosal T lymphocytes in intestinal growth, development and enteropathy

Over the past 15-20 years, research has progressively focused on the mucosal T cell as the central factor in the initiation of physiological or pathological changes, first in the growth and maturation of the early (postnatal) intestine, and second in adult-type enteropathies resulting from sensitivity to either food or pathogen-derived antigens. T cell-mediated events may be measured, for example, in terms of specific immunopathologic patterns of change and injury, such as type 1 (lymphocyte infiltration), type 2 (crypt hyperplasia) and type 3 (flat-destructive), which can be recognized and quantitated microscopically; by determination of lymphocyte reactivity through secretion of interleukin-2 receptors (IL-2R) into plasma or expression by mucosal lymphocytes; by quantitation of lymphocyte subsets emigrating into inflamed tissues by immunoperoxidase-labelled monoclonal antibodies; or by the determination of T cell receptor polymorphisms. Alterations in intestinal growth, structure and function at weaning are likely to be T cell-mediated as they are analogous to the same type 1/2 lesions that reflect modulation of adult mucosal architecture in food and parasite-induced hypersensitivity reactions. Enteropathies associated with HIV infection and T cell deficiency display a milder degree of villous flattening and impaired crypt hyperplasia than that typical of gluten-sensitivity, suggesting a reversion to lesser degrees of mucosal pathology (type 1/2). Clearly more information will accrue; meanwhile the remarks in this brief survey should provide a firm basis whereby clinician and scientist can meet, and together recognize and further dissect the modulatory effect of T lymphocytes on mucosal structure and function.