Immunohistological studies of surface antigen on colonic lymphoid cells in normal and inflamed mucosa. Comparison of follicular and lamina propria lymphocytes

New Targeted Therapies for Uncontrolled Asthma

Mechanistic studies have improved our understanding of molecular and cellular components involved in asthma and our ability to treat severe patients. An mAb directed against IgE (omalizumab) has become an established add-on therapy for patients with uncontrolled allergic asthma and mAbs specific for IL-5 (reslizumab, mepolizumab), IL-5R (benralizumab), and IL-4R (dupilumab) have been approved as add-on treatments for uncontrolled eosinophilic (type 2) asthma. While these medications have proven highly effective, some patients with severe allergic and/or eosinophilic asthma, as well as most patients with severe non-type-2 disease, have poorly controlled disease. Agents that have recently been evaluated in clinical trials include an antibody directed against thymic stromal lymphopoietin, small molecule antagonists to the chemoattractant receptor-homologous molecule expressed on T_H2 cells (CRTH2) and the receptor for stem cell factor on mast cells (KIT), and a DNA enzyme directed at GATA3. Antibodies to IL-33 and its receptor, ST2, are being evaluated in ongoing clinical studies. In addition, a number of antagonists directed against other potential targets are under consideration for future trials, including IL-25, IL-6, TNF-like ligand 1A, CD6, and activated cell adhesion molecule (ALCAM). Clinical data from ongoing and future trials will be important in determining whether these new medications will offer benefits in place of or in addition to existing therapies for asthma.

Lack of Decay of HIV-1 in Gut-Associated Lymphoid Tissue Reservoirs in Maximally Suppressed Individuals

Although peripheral blood mononuclear cells (PBMCs) and lymph nodes represent a principal reservoir, the contribution of gut-associated lymphoid tissue (GALT) has not been evaluated. In 15 HIV-1-infected subjects with maximal suppression of HIV replication by highly active antiretroviral therapy, we quantified HIV-1 DNA and RNA in mucosal biopsy specimens, PBMCs, and plasma with ultrasensitive assays. We also calculated compartmental burdens of HIV-1 DNA-positive cells and characterized the temporal decay of these reservoirs in a period of 1 year (with projections to >50 years). HIV-1 RNA was detected in 20% of the subjects' mucosal biopsy specimens and in 80% of the PBMC samples. Mucosal HIV-1 DNA was detected in 80% of the subjects and in 100% of the PBMC samples. Calculated numbers of lymphoid cells containing "potentially replication-competent" HIV-1 DNA showed that the PBMC compartment contained approximately 70,000 such cells, and GALT contained approximately 160,000 cells. Rates of decay slopes for all 15 subjects in both compartments were not statistically significantly different when compared with each other or with zero slope. Our data indicate that GALT is a quantitatively important reservoir of potentially replicative cells containing HIV-1 DNA, harboring at least as many or more of such cells as the PBMC compartment. In well-suppressed patients on highly active antiretroviral therapy, the GALT compartment showed no clear pattern of HIV-1 decay, similar to that in the PBMCs.

Bacterial-reactive T regulatory cells inhibit pathogenic immune responses to the enteric flora

We showed previously that cecal bacterial Ag (CBA)-specific CD4(+) T cells induce colitis when transferred into SCID mice. The purpose of this study was to generate and characterize CBA-specific regulatory T cells in C3H/HeJBir (Bir) mice. CD4(+) T cells were stimulated with CBA-pulsed APC in the presence of IL-10 every 10-14 days. After four or more cycles, these T cells produced high levels of IL-10, low levels of IL-4 and IFN-gamma, and no IL-2, consistent with the phenotype of T regulatory-1 (Tr1) cells. Bir Tr1 cells proliferated poorly, but their proliferation was dependent on CD28-B7 interactions and was MHC class II-restricted. Transfer of Bir Tr1 cells into SCID mice did not result in colitis, and cotransfer of Bir Tr1 T cells with pathogenic Bir CD4(+) Th1 cells prevented colitis. Bir Tr1 cells inhibited proliferation and IFN-gamma production of a CBA-specific Th1 cell line in vitro. Such inhibition was partly due to IL-10 and TGFbeta1, but cognate interactions with either APCs or Th1 cells were also involved. Normal intestinal lamina propria CD4(+) T cells had Tr1-like activity when stimulated with CBA-pulsed APCs. We conclude that CD4(+) T cells with the properties of Tr1 cells are present in the intestinal lamina propria and hypothesize that these cells maintain intestinal immune homeostasis to the enteric flora.

Differentiation between ulcerative colitis and Crohn's disease by a quantitative immunohistochemical evaluation of T lymphocytes, neutrophils, histiocytes and mast cells

Mucosal biopsy criteria has limited validity in terms of discrimination between ulcerative colitis (UC) and Crohn's disease (CD). The aim of this study was to set up quantitative immunohistochemical criteria, with a special focus on inflammatory cell distribution within individual specimens and throughout the large bowel. Quantitative evaluation was performed for the density of CD8+, CD45RO+, neutrophil elastase+, CD68+ and mast cell tryptase+ cells in affected and unaffected mucosa taken from 41 patients with UC and 61 patients with CD. Each slide was examined at the highest and lowest density fields, which were further divided into the upper and deeper half of mucosa. Multiple logistic regression analysis using 51 features as independent variables constructed a predictive equation finding the probability of UC (PUC), and the diagnostic categories were subsequently defined based on a receiver-operating characteristic curve. The analysis disclosed five significant features suggesting UC; these implied intense infiltration of CD8+ and mast cell tryptase+ cells, diffuse infiltration of neutrophil elastase+ and CD68+ cells, and continuous infiltration of CD45RO+ cells. The criteria consisted of three diagnostic categories, 'suggestive of UC (PUC > or = 0.7)', 'indeterminate (0.3 < PUC < 0.7)', and 'suggestive of CD (PUC < or = 0.3)'; the criteria had values for sensitivity and specificity exceeding 95%. The immunohistochemical criteria distinguishing UC from CD may help to confirm the diagnosis in patients with ambiguous endoscopic and histological diagnosis.

Enhanced levels of functional HIV-1 co-receptors on human mucosal T cells demonstrated using intestinal biopsy tissue

OBJECTIVE

To examine compartmental differences in co-receptor expression on CD4 lymphocytes between blood and gut using endoscopic biopsies.

DESIGN

Mucosal and peripheral CD4 T cells from healthy controls were compared for co-receptor expression and vulnerability to infection by HIV-1.

METHODS

Expression of CCR5 and CXCR4 was quantified by flow cytometry on isolated mucosal CD4 lymphocytes obtained from endoscopic biopsies and blood from healthy controls. Vulnerability to in vitro infection by both R5 and X4 strains was assessed by measuring p24.

RESULTS

Biopsies yielded sufficient lymphocytes for flow cytometric characterization and infectivity studies. The percentage of mucosal CD4 T lymphocytes that expressed CCR5 and the per cell expression of CCR5 were both significantly increased compared with that in peripheral blood CD4 T lymphocytes. CXCR4 was expressed on the majority of CD4 lymphocytes in both compartments. In vitro infection of mucosal mononuclear cells supported greater viral replication of both R5 and X4 strains than peripheral blood mononuclear cells.

CONCLUSIONS

Enhanced expression of CXCR4 and CCR5 on CD4 lymphocytes in normal intestinal mucosa predicts increased vulnerability to infection by both R5 and X4 HIV-1. Endoscopic biopsies provide a useful mucosal tissue sampling technique to identify compartmental immunologic differences that may be exploited by HIV-1 in establishing initial mucosal infection.

Distal proctocolitis and n-3 polyunsaturated fatty acids (n-3 PUFAs): the mucosal effect in situ

It has been postulated that patients with ulcerative colitis (UC) have altered reactivity of gut-associated lymphoid tissue. In such cases there is intense infiltration of the mucosa with immune competent cells and associated tissue damage. We have shown previously that the dietary supplementation with the n-3 polyunsaturated fatty acids (n-3 PUFAs), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) results in significant systemic immune suppression. The aim of this study, therefore, was to evaluate the in situ effect of n-3 PUFAs on distal proctocolitis. Each patient received either fish oil extract (EPA 3.2 g, DHA 2.4 g) (n = 9) or sunflower oil (n = 9) daily in a double blind manner for six months. Monthly assessment included: (1) disease activity using clinical, sigmoidoscopic, and histological scores and (2) immunohistochemical analysis (immunoglobulins, CD profiles) of rectal biopsy specimens (before and after six months supplementation) using monoclonal antibodies and quantitative computer-assisted video image analysis. Prior to receiving supplementation, patients with proctocolitis (n = 18) showed significantly higher numbers of cells expressing CD3 (pan T cells) and HLA-DR and IgM containing cells compared with non-colitic controls (n = 8). Six months supplementation with n-3 PUFAs resulted in significant reduction in the number of cells expressing CD3 and HLA and the percentage of cells containing IgM. There was no significant change in the CD20 nor the percentage of IgG or IgA containing cells in either group of patients with procto-colitis. In patients receiving n-3 PUFA supplementation, there was improvement in the disease activity and histological scores, compared with pretreatment evaluation. This study has demonstrated both evidence of suppression of in situ immune reactivity and concurrent reduction in disease activity in patients with proctocolitis receiving n-3 PUFA supplementation. This may have important implication for therapy in patients with ulcerative colitis.

Interleukin-6 and soluble interleukin-6 receptor in the colonic mucosa of inflammatory bowel disease

BACKGROUND

Interleukin-6 (IL-6) has multiple immunological effects on a wide variety of cells and tissues. The expression of IL-6 and IL-6 receptor (IL-6R) may be important to the pathogenesis of inflammatory bowel disease (IBD).

METHODS

In the present study, we examined whether mucosal IL-6 and soluble IL-6R were associated with the pathophysiology of IBD using the colonic mucosal specimens obtained from patients with IBD. Enzyme-linked immunosorbent assay was used to measure the levels of IL-6 and sIL-6R in organ cultures of mucosal tissues and in cell cultures of fractionated mucosal cells as well as in the serum. Expression of IL-6 and IL-6R was analysed by reverse transcription-polymerase chain reaction analysis using freshly isolated lamina propria mononuclear cells (LPMC).

RESULTS

The levels of IL-6 and sIL-6R in organ cultures were substantially elevated in patients with IBD, especially in those with histologically active inflammation. In contrast, considerably higher levels of sIL-6R were detected in patients with other types of colonic inflammation who were included as inflammatory controls, but elevation of IL-6 was less prominent in such patients. The positivity for expression of IL-6 and IL-6R mRNA in LPMC was in parallel with the results obtained in organ cultures. In cell cultures, mucosal macrophages were the main cell type producing both IL-6 and sIL-6R on a per cell basis and other cell fractions including colonic epithelial cells and lymphocytes produced substantially lower amounts of these molecules. The levels of IL-6 and sIL-6R in organ cultures, but not those in the serum, showed a significantly positive correlation with the degree of clinical disease activity in patients with IBD.

CONCLUSIONS

Enhanced IL-6/sIL-6R-mediated immune and inflammatory responses may be implicated, at least partly, in the continuation of intestinal inflammation in patients with IBD.

A quantitative immunohistochemical evaluation of inflammatory cells at the affected and unaffected sites of inflammatory bowel disease

Levels of T lymphocytes, histiocytes and mast cells have been reported to be increased in the affected mucosa of Crohn's disease (CD) and ulcerative colitis (UC), but the colorectal distribution of these cells is not fully understood. We hypothesized that differences in cell densities between CD and UC would be characteristic, not only in the affected, but also in the unaffected mucosa. The aims of the present study were to clarify whether there were any differences in cell densities in CD, UC and infectious colitis (IC) in the affected mucosa and between CD and UC in the unaffected mucosa. Using mouse monoclonal antibodies recognizing memory T cells (OPD4), cytotoxic/suppressor T cells (C8/144B), histiocytes (PG-M1) and mast cells (AA1), we evaluated mucosal cell densities in biopsy specimens from both endoscopically affected and unaffected sites of CD (n = 12) and UC (n = 15) and from affected sites of IC (n = 10). Ten normal controls were also examined. At affected sites, all cells were significantly more abundant in UC than in the other conditions, except that the density of PG-M1+ in CD was similar to that seen in UC. Although the densities of OPD4+ and C8/144B+ cells at unaffected sites were slightly higher in both CD and UC and in UC, respectively, there was no significant difference in cell densities between CD and UC. The ratio of OPD4+ cell density at affected sites to that at unaffected sites was appreciably higher in UC than in CD. The results suggest that a common feature of UC and CD is an increase in PG-M1+ cells at the affected mucosa but that the other inflammatory cells studied are more abundant, particularly in UC, and that the difference between UC and CD is conspicuous when comparing the OPD4+ cell density of the affected mucosa with that of the unaffected mucosa.

Epstein-Barr virus expression in Hodgkin's disease: Correlation with histologic subtypes and T and B lymphocyte distribution

BACKGROUND

The pathogenesis of Hodgkinâs disease (HD) has been linked to Epstein-Barr virus (EBV). Some histologic subtypes show a high level of viral expression. These include mixed cellularity (MCHD) and nodular sclerosis (NSHD) subtypes. Grade II NSHD is a more aggressive variant of HD. Lymphocyte predominant (LPHD) is a B cell lymphoproliferative disorder that has not been associated with EBV expression. Infiltrating lymphocytes in HD are predominantly T lymphocytes, with a minor component of B lymphocytes. In the current study, EBV expression was tested in cases of HD in relation to histologic subtypes. An attempt was made at correlating EBV expression with T and B lymphocyte distribution in lymph nodes involved by HD.

METHOD

Formalin-fixed paraffin-embedded tissue from 62 cases of HD were tested for EBV mRNA expression, using the EBER-1 probe and in situ hybridization. T and B lymphocyte distribution and their ratios were evaluated using antibodies to T and B lymphocytes (UCHL-1 [CD45 RO] and CD 20, respectively), and the immunoperoxidase technique.

RESULTS

The cases were seen in 38 male and 24 female patients, with an age range of 3 to 72 years (median 25 years). There were 30 cases of grade I and 15 cases of grade II NSHD, 9 cases of MCHD and 8 cases of LPHD. EBV mRNA expression was seen in 29 cases (46%). This expression was seen in 8 cases of grade I NSHD (26%), 13 cases of grade II NSHD (86%) and 8 cases of MCHD (88%). None of the cases of LPHD showed viral expression. T to B lymphocyte ratios in EBV-positive cases ranged from 1/6 to 8/1, and ranged from 2/1 to 20/1 in EBV-negative cases (P=0.06). Nine of the 29 positive cases (31%) showed equal T/B lymphocyte ratios (n=4), or predominance of B lymphocytes (n=5). None of the EBV-negative cases showed predominance of B lymphocytes.

CONCLUSION

Our study confirms previously reported findings of the prevalence of EBV expression in MCHD and NSHD. Our findings also suggest that EBV expression may be more commonly seen in aggressive forms of HD. Decreased numbers of T lymphocytes in these aggressive subtypes may suggest that a process of more profound T lymphocyte depletion is occurring in these cases, leading to uncontrolled EBV replication and more aggressive disease.

Differences in immunophenotyping of mucosal lymphocytes between ulcerative colitis and Crohn's disease

OBJECTIVES

Immunologic studies have characterized the numbers and types of inflammatory cells in diseased inflammatory bowel disease (IBD) mucosa but have yielded conflicting results regarding intestinal lymphocytes activation in IBD. We investigated the levels of lymphocytes subsets, interleukin-2 receptor, transferrin receptor, and T cell receptors in mainly isolated lamina propria lymphocytes. Including intraepithelial lymphocytes of normal colonic mucosa or IBD (ulcerative colitis and Crohn's disease) mucosa to understand the pathogenesis of IBD. We have results from this study.

RESULTS

1) In comparing ulcerative colitis with control, IL-2R (p < 0.05), TR (p < 0.01), and CD3/HLA-DR (< 0.05) showed a significant increase. 2) In comparing Crohn's disease with control, CD3 (P < 0.05), TCR alpha/beta (p < 0.01) and TCR gamma/delta (p < 0.05) showed a significant decrease. 3) In comparing Crohn's disease with ulcerative colitis, CD19 (p < 0.01), TR (p < 0.01), TCR alpha/beta (p < 0.01) and TCR gamma/delta (p < 0.05) showed a significant decrease.

CONCLUSION

From these results, there are increased T cell markers, IL-2R, TR, and CD3/HLA-DR in UC, but differently, decreased CD3, TCR alpha/beta and TCR gamma/delta in CD compared with control. In addition, definitive differences in lymphocytes markers, CD19, TR, TCR alpha/beta and TCR gamma/delta, which are higher in UC than in CD, may elucidate the different immunopathogenesis between UC and CD.

B- and T-Lymphocyte distribution in benign and malignant lymphoepithelial lesions of the parotid gland: Correlation with Epstein-Barr virus expression and a proposed mechanism of malignant transformation

Epstein-Barr virus expression in malignant lymphoepithelial lesions (LEL) of the parotid gland has been well established. The virus is occasionally expressed in benign LEL, especially in immunocompromised hosts. The pathogenesis of the disease as it relates to virus expression and lymphocyte subsets has not been clearly defined. In this study, we attempted to identify B- and T-lymphocyte distribution in the lesions as it relates to EBV expression in LELs of the parotid gland. Formalin-fixed paraffin-embedded sections of 18 cases of LEL of the parotid gland were immunohistochemically tested for the distribution of B- and T-lymphocytes in the lesions, using the antibodies L-26 (CD 20) for B-lymphocytes and UCHL-1 (CD-45RO) for T-lymphocytes. The sections were also tested by in situ hybridization for EBV mRNA expression, using the EBER-1 probe specific for EBV-1 gene. The 18 lesions included seven malignant LEL, seven benign LEL and four benign lymphoepithelial cysts. All malignant LELs showed a high and diffuse level of epithelial expression of EBV mRNA. Of the 11 benign lesions, only one case showed focal epithelial expression of EBV mRNA. This was a case of benign LEL in an HIV-positive male. All the benign lesions, except that expressing EBV mRNA, showed a T-/B-lymphocyte ratio averaging 2:1. All cases expressing EBV mRNA, including the case of benign LEL in the HIV-positive patient, showed a T-/B-lymphocyte ratio averaging 1:3. Our findings suggest that a T-lymphocyte-mediated immune response may play an essential role in suppressing proliferation of EBV in benign LEL of the parotid gland. This immune mechanism may be significantly disturbed in the malignant lesions, leading to uncontrolled viral replication and carcinogenesis.

Intraepithelial and lamina propria leucocyte subsets in inflammatory bowel disease: an immunohistochemical study of colon and rectal biopsy specimens

AIMS

To gain new insights into the pathogenesis and differential diagnosis of ulcerative colitis and colonic Crohn's disease.

METHODS

Immunohistochemistry for different leucocyte subsets was performed in biopsy specimens of the sigmoid colon and rectum from 55 patients with inflammatory bowel disease and 11 healthy controls.

RESULTS

Colonic biopsy specimens from patients with active ulcerative colitis had significantly higher numbers of CD45+ and CD3+ leucocytes compared with those from patients with inactive disease, and higher numbers of total leucocytes and macrophages than those from patients with Crohn's disease. Rectal biopsy specimens from patients with Crohn's disease had greater numbers of intraepithelial leucocytes (CD45, CD3 and CD8 cells) than specimens from patients with active or inactive ulcerative colitis, or from healthy controls.

CONCLUSIONS

Because of the phenotypic differences in the inflammatory infiltrate in the mucosa from the sigmoid colon and the rectum, the segment of the intestine to be biopsied should be specified. Assessment of the leucocytic component of the intraepithelial infiltrate in rectal biopsy specimens was more useful than examination of colonic biopsy specimens in the differential diagnosis of ulcerative colitis and Crohn's disease.

Elevation of interleukin-6 in inflammatory bowel disease is macrophage- and epithelial cell-dependent

Local interleukin-6 (IL-6) activity was studied using colonic mucosal tissues in inflammatory bowel disease (IBD) and inflammatory control patients. Active IBD specimens exhibited significantly higher IL-6 activity than control specimens in both cultures of isolated lamina propria mononuclear cells (LPMC) and mucosal tissues with an increased number of IL-6-producing cells. However, the activity in inactive IBD or inflammatory controls did not differ from controls. Northern blot analysis demonstrated IL-6 messenger RNA in LPMC and colonic epithelial cells isolated from active IBD specimens but not in control cells. Furthermore, immunofluorescent microscopic study of active IBD specimens showed more conspicuous staining of IL-6 in infiltrating LPMC (mostly CD68+ cells) and colonic epithelial cells. These results suggest that elevation of local IL-6 activity may be a characteristic feature of active IBD and both macrophages and colonic epithelial cells are the major cell types responsible for this phenomenon.

Phenotypic and immunoregulatory analysis of intestinal T-cells in patients with inflammatory bowel disease: evaluation of an in vitro model

Although a disturbed immune response to constituents of the gut mucosa has been implicated in the pathogenesis of inflammatory bowel disease, the mechanisms are still unclear. Intestinal T-cells derived from gut biopsies were propagated in vitro as single and co-cultures under different experimental conditions prior to flow cytometry. Intestinal T-cell lines from inflamed mucosa (n = 69) showed a significant (P < 0.001) decrease in CD4+ T-cells compared to T-cells from normal (n = 49) and uninflamed (n = 29) tissue specimens. Co-culturing of inflamed and uninflamed mucosa led to a normalization of CD4+ T-cells in cultures derived from inflamed mucosa. Analysis of supernatants revealed a significantly (P < 0.001) increased secretion of IL-4 under co-culture conditions. Moreover, stimulation of cultures derived from inflamed mucosa with rIL-4 led to a significant (P < 0.001) increase in CD4+ T-cells, whereas anti-IL-4 antibodies or IFN-gamma supplementation of T-cells derived from uninflamed mucosa significantly (P < 0.001) reduced the CD4+ subset. Treatment with IFN-gamma and anti-IL-4 antibodies did not affect the phenotype of T-cells derived from inflamed mucosa. These data suggest that IL-4 might play a key role in the intestinal immune response. Furthermore, this in vitro system allows the investigation of mucosal immune mechanisms in more detail under standardized conditions.

Pitfalls in the characterization of small intestinal lymphocytes

The morphological characteristics of human intestinal lymphocytes may vary depending upon whether they are examined in tissue sections or after isolation. This study uncovered some causes of these discrepancies. The majority of intraepithelial lymphocytes (IEL) and lamina propria lymphocytes (LPL) are of the same size and granularity as peripheral blood mononuclear cells (PBMC), negating the idea that most IEL are large granular lymphocytes. LPL were previously shown to express markers of early activation by flow cytometry but not by immunohistochemistry. This study shows that it is the low density of surface antigen expression that explains this discrepancy: only the highly sensitive flow cytometric analysis can detect such low-density expression. Previous reports of intestinal macrophage and B cell numbers and functions vary markedly. This may be due to variable amounts of contamination with epithelial cells (EC) that lose their characteristic columnar appearance and cytoplasmic mucin upon isolation. They share many features of macrophages (such as morphology and binding to plastic and latex beads) but lack phagocytic ability and superoxide generation, explaining, perhaps, the wide variation in the reported functions of presumed intestinal macrophages. In addition, a large fraction of EC non-specifically strain with anti-immunoglobulin antibodies. Their contamination of intestinal lymphocyte preparations accounts for the discrepancy in B cell numbers identified by surface immunoglobulin expression versus B cell markers. Intestinal lymphocytes do indeed differ in many ways from circulating lymphocytes, but investigators must be attentive to factors that may artifactually alter their results.

Alterations in the mucosal immune system in ulcerative colitis and Crohn's disease

Emphasis is now being placed upon obtaining a better understanding of the regulatory cytokines that normally downregulate acute intestinal inflammation. These inhibitory cytokines appear to be missing or not functioning properly in patients with inflammatory bowel disease (IBD), thereby leading to perpetuation of inflammation. As we obtain an increased understanding of immune and inflammatory regulatory processes in the intestine, we will be able to devise better future therapeutic strategies for use in our IBD patients.

Expression of adhesion molecules and HLA-DR by macrophages and dendritic cells in aphthoid lesions of Crohn's disease: an immunocytochemical study

The phenotypes and ultrastructure of macrophages and dendritic cells in aphthoid lesions of the colon were immunocytochemically observed in patients with Crohn's disease. Biopsy specimens were endoscopically obtained from both aphthoid and advanced lesions in Crohn's disease patients. Biopsy specimens obtained from patients with infectious colitis and from normal individuals served as controls. Aphthoid lesions contained densely aggregated CD68+ macrophages, which were surrounded by numerous ID-1+ dendritic cells. In the normal controls and infectious colitis patients, however, a few scattered CD68+ macrophages and ID-1+ dendritic cells were noted beneath the surface epithelium. CD3+ lymphocytes were significantly increased in both aphthoid and advanced lesions of Crohn's disease, but the CD4/CD8 ratio was similar in all groups studied. The double immunoperoxidase staining method revealed that both CD68+ macrophages and ID-1+ dendritic cells in the aphthoid lesions simultaneously expressed ICAM-1 and HLA-DR antigens. Electronmicroscopic observation revealed that CD68+ macrophages had numerous vesicles and lysosomal granules and few projections, and that ID-1+ dendritic cells had appreciable cytoplasmic protrusions with a few vacuoles. These findings suggested that the colonic mucosa in Crohn's disease contained two types of macrophage/dendritic cells in the same lineage that expressed intercellular adhesion molecules and class-II MHC antigens. It also appeared that the aphthoid lesions of Crohn's disease featured an increase in macrophages and dendritic cells consistent with immunological activation.

Immune activation genes in inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease is associated with enhanced activation of T cells, but the genes responsible for this state are not well characterized.

METHODS

T-cell activation genes were studied in peripheral blood and intestinal mucosal mononuclear cells of control, Crohn's disease, and ulcerative colitis patients.

RESULTS

In all groups the expression of interleukin-2 (IL-2), IL-2 receptor alpha (IL-2R alpha), and IL-2R beta messenger RNA (mRNA) was significantly higher in intestinal than circulating cells, and it correlated well with protein levels. Both IL-2R alpha and IL-2R beta mRNA were abundant in mucosal cells, suggesting that a substantial number of them displays high affinity IL-2R. This would explain why intestinal cells proliferate more, express more IL-2 transcripts, and secrete more IL-2 than peripheral cells. Inflammatory bowel disease cells produced similar or higher IL-2R alpha and IL-2R beta mRNA than controls but generated significantly lower IL-2 mRNA. Thus, the reported defect of IL-2 activity in Crohn's disease and ulcerative colitis is probably related to decreased IL-2 transcription. Crohn's disease intestinal cells had the highest expression of IL-2R gene products. This provides a mechanism for their increased response to IL-2 and supports claims that elevated soluble IL-2R alpha serum levels reflect gut T-cell hyperactivity in this disease.

CONCLUSIONS

These findings underscore the importance of T cells in mucosal immunity and indicate that abnormal T-cell activation is intimately associated to the pathogenesis of inflammatory bowel disease.

Subacute cutaneous lupus erythematosus in a patient with Crohn's disease

A case of anti-Ro (SS-A) antibody-positive subacute cutaneous lupus erythematosus (LE) occurring in a 47-year-old male with Crohn's disease is described. This is a previously undescribed association.

Increased in vitro release of soluble interleukin 2 receptor by colonic lamina propria mononuclear cells in inflammatory bowel disease

Increased concentrations of the soluble form of the interleukin 2 receptor have been observed in the sera of Crohn's disease and ulcerative colitis patients. In this study we have observed the spontaneous release of soluble interleukin 2 receptor by unstimulated, isolated normal and inflammatory bowel disease colonic lamina propria mononuclear cells. Lamina propria mononuclear cells from Crohn's disease patients (median = 204 U/ml (interquartile range 126-396, n 17) secreted significantly (p less than 0.01) more soluble interleukin 2 receptor than normal controls (median = 124.5 U/ml (108-131), n 12). No statistically significant differences were seen between ulcerative colitis (median = 135 U/ml (92-196), n 20) and normal controls. Moreover, significantly (p less than 0.01) increased amounts of soluble interleukin 2 receptor were secreted by colonic diverticulitis lamina propria mononuclear cells (median = 259 U/ml (149-282), n 15) which were used as disease specificity controls. Time course experiments showed that the majority of soluble interleukin 2 receptor was released by isolated lamina propria mononuclear cells in the first six days of culture. Upon stimulation with pokeweed mitogen, Crohn's disease (median = 2258 U/ml (1435-3584), n 14), normal control (median = 2622 U/ml (2030-3180), n 14) and diverticulitis lamina propria mononuclear cells (median = 2745 U/ml (1733-3192), n 10) reached similar maximal soluble interleukin 2 receptor secretion levels, while ulcerative colitis lamina propria mononuclear cells secreted significantly (p less than 0.005) less soluble interleukin 2 receptor (median = 912 U/ml (494-1259), n 17). These results suggest that enhanced shedding/secretion of soluble interleukin 2 receptor by intestinal lymphocytes may account in part for increased serum soluble interleukin 2 receptor concentrations during chronic intestinal inflammatory reactions.

The CD56 adhesion molecule is the major determinant for detecting non-major histocompatibility complex-restricted cytotoxic mononuclear cells from the intestinal lamina propria

In this study, specific antibodies against natural killer (NK) cell surface markers identify these cells to be commonly present in normal intestinal mucosa of inflammatory bowel disease (IBD) and carcinoma patients. Cells expressing the CD56 adhesion molecule were found to be far more abundant than CD16+ cells. Functional studies revealed that cells mediating non-major histocompatibility complex-restricted cytotoxicity (NK activity) in the lamina propria express the CD56 surface antigen, whereas only a minority of this activity resides in the population with CD16 expression. This is in contrast with peripheral blood NK cells, which were found to be almost exclusively both CD16+ and CD56+. Moreover, in the lamina propria of the intestine we found CD3+ T lymphocytes not to be involved in spontaneous cell-mediated killing of tumor cells. Considerably higher numbers of cells with the CD16 or CD56 surface markers were found to be present in normal mucosa of IBD patients compared with normal mucosa of carcinoma patients, which was also reflected in higher levels of cytotoxicity detected in lamina propria mononuclear cell preparations from normal IBD mucosa. Because of the disease-related localization of the mucosa studied from both patient groups, i.e. ileum vs. colon, the observed differences may be related to tissue characteristics. Within the IBD group, relatively high levels of cytotoxicity were found in cell preparations from normal mucosa of Crohn's disease patients compared with ulcerative colitis patients, which might support the current concept that Crohn's disease affects the whole of the gastrointestinal tract.

Two-color immunofluorescence and flow cytometric analysis of lamina propria lymphocyte subsets in ulcerative colitis and Crohn's disease

By using two-color immunofluorescence with fluorescein isothiocyanate (FITC) and phycoerythrin (PE)-labelled monoclonal antibodies and multiparameter flow cytometry, we investigated lamina propria lymphocyte subsets of patients with ulcerative colitis (UC) and Crohn's disease (CD). Leu-3/Leu-2 (CD4/CD8) ratio of lamina propria lymphocytes (LPL) of CD (mean +/- SD: 1.9 +/- 0.8, P less than 0.01) was significantly decreased compared with controls (3.3 +/- 1.1), because of an increased number of CD8+ lymphocytes. The majority of lamina propria CD4+ cells were CD4+, Leu-8- and CD4+, CD45R- both in controls and IBD tissue. Many lamina propria T lymphocytes were activated, expressing HLA-DR antigen not only in IBD but also in controls. NK cells defined by CD16 and CD 56 (3.0 +/- 1.4%, P less than 0.01) were significantly decreased in patients with UC compared with controls (6.5 +/- 3.0%). A low proportion of B cells in the intestinal mucosa expressed Leu-8 antigen and CD23 antigen. The proportion of activated B cells of LPL was high in IBD mucosa as well as normal mucosa. These findings suggest that local activation of B cells leads to the loss of the expression of Leu-8 antigen and CD23.

Increased activation of isolated intestinal lamina propria mononuclear cells in inflammatory bowel disease

Normal human lamina propria lymphocytes are in a heightened state of activation compared with peripheral blood with regard to cell-surface activation antigen expression (transferrin receptor, interleukin-2 receptor, 4F2) and the increased spontaneous secretion of immunoglobulins in vitro. This study evaluates the cell-surface expression of activation-associated antigens in different subpopulations of isolated colonic lamina propria mononuclear cells in inflammatory bowel disease. In pilot studies using three-color flow cytometry, autofluorescence was observed that was emitted by unstained lamina propria mononuclear cells, which interfered with both the sensitivity and the specificity of the analyses. Because a major portion of the intestinal lymphocyte populations of interest were autofluorescent, a method to remove autofluorescence signals was developed by designing a computer program for the subtraction of autofluorescence from the emissions of each individual cell. This technique increases both the sensitivity and specificity of flow-cytometric analyses of intestinal lamina propria mononuclear cells. Using fluorescence-activated cell-sorter analyses with subtraction of autofluorescence on a single-cell basis, increased expression of lymphocyte activation antigens (interleukin-2 receptor, transferrin receptor, 4F2) was found on the cell surface of isolated intestinal B cells, T cells, CD4+ T cells, and CD8+ T cells in both Crohn's disease and ulcerative colitis. Therefore, markedly increased intestinal lymphocyte activation is a major immunological alteration in inflammatory bowel disease and includes all lymphocyte subpopulations investigated in this study. In addition, 5-aminosalicylic acid, which is used for the treatment of intestinal inflammation in inflammatory bowel disease, inhibits the expression of cell-surface activation antigens on mitogen-activated peripheral blood lymphocytes in a dose-dependent manner. These observations suggest that lymphocyte activation may play an important role in underlying immune processes that lead to chronicity and perpetuation of inflammatory bowel disease and may implicate an additional mechanism for the therapeutic action of 5-aminosalicylic acid.