Intestinal tissue transglutaminase in coeliac disease of children and adults: ultrastructural localization and variation in expression

BACKGROUND: Tissue transglutaminase is the main antigen for the anti-endomysial antibodies used for diagnosis of coeliac disease and can with some specificity in vitro deamidate gliadins generating potent epitopes. The intestinal levels and the ultrastructural localization of tissue transglutaminase in normal and affected persons were investigated to provide further information on its role in this disease. Intestinal biopsies were taken from normal and coeliac children and adults. METHODS: The level of transglutaminase was analysed by means of a quantitative enzymatic assay and its ultrastructural localization by immunogold electronmicroscopy using a monoclonal antibody against tissue transglutaminase. RESULTS: In relation to normal individuals, the enzymatic activity of tissue transglutaminase in adult coeliac patients was increased. The enzyme was found in the enterocytes and in increased amount just beneath the enterocytes, where cytosolic and nuclear labelling of distinct elongated cells was seen in addition to extracellular labelling close to collagen fibrils. In children, the enzymatic activity and the immunogold labelling could not be shown to be related to disease. In all cases the enzyme activity was EDTA-sensitive. CONCLUSIONS: The increased amount of tissue transglutaminase activity in coeliac adults was shown to be due to the appearance of the enzyme in enterocytes and increased expression in the lamina propria. No evidence was found to support the idea of a changed localization or changed amounts as primary elements in coeliac disease pathogenesis, nor for the involvement of non-calcium dependent microbial transglutaminases.     

Dissection of T-cell antigen specificity in human melanoma

Tumor-infiltrating lymphocytes (TIL) isolated from melanoma patients and expanded in vitro by interleukin (IL)-2 treatment can elicit therapeutic response after adoptive transfer, but the antigen specificities of the T cells transferred have not been determined. By compiling all known melanoma-associated antigens and applying a novel technology for high-throughput analysis of T-cell responses, we dissected the composition of melanoma-restricted T-cell responses in 63 TIL cultures. T-cell reactivity screens against 175 melanoma-associated epitopes detected 90 responses against 18 different epitopes predominantly from differentiation and cancer-testis antigens. Notably, the majority of these responses were of low frequency and tumor-specific T-cell frequencies decreased during rapid expansion. A further notable observation was a large variation in the T-cell specificities detected in cultures established from different fragments of resected melanoma lesions. In summary, our findings provide an initial definition of T-cell populations contributing to tumor recognition in TILs although the specificity of many tumor-reactive TILs remains undefined.     

Congenital myasthenic syndromes: recent advances

Congenital myasthenic syndromes (CMS) can arise from presynaptic, synaptic, or postsynaptic defects. Mutations of the acetylcholine receptor (AChR) that increase or decrease the synaptic response to acetylcholine (ACh) are a common cause of the postsynaptic CMS. An increased response occurs in the slow-channel syndromes. Here, dominant mutations in different AChR subunits and in different domains of the subunits prolong the activation episodes of AChR by either delaying channel closure or increasing the affinity of AChR for ACh. A decreased synaptic response to ACh occurs with recessive, loss-of-function mutations. Missense mutations in the low-affinity, fast-channel syndrome and in a disorder associated with mode-switching kinetics of AChR result in brief activation episodes and reduce the probability of channel opening. Mutations causing premature termination of the translational chain or missense mutations preventing the assembly or glycosylation of AChR curtail the expression of AChR. These mutations are concentrated in the epsilon subunit, probably because substitution of the fetal gamma for the adult epsilon subunit can rescue humans from fatal null mutations in epsilon. Recent molecular genetic studies have also elucidated the pathogenesis of the CMS caused by absence of the asymmetric form of acetylcholinesterase from the synaptic basal lamina. Endplate acetylcholinesterase deficiency is now known to be caused by mutations in the collagenic tail subunit of the asymmetric enzyme that prevents the association of the collagenic tail subunit with the catalytic subunit or its insertion into the basal lamina.     

HLA-G polymorphisms and HLA-G expression in sarcoidosis

BACKGROUND: The MHC class Ib molecule Human Leukocyte Antigen (HLA)-G may be important in induction and maintenance of immunological tolerance, and HLA-G expression may have a role in different cancers, in certain diseases with associations to HLA, and in organ transplantation. Sarcoidosis is a systemic granulomatous disease with unknown etiology but at the molecular level several studies have shown HLA associations. METHODS: In the present study, HLA-G alleles/polymorphisms were studied in sarcoidosis patients (n = 47) and controls (n = 129) by PCR techniques and HLA-G protein expression was investigated in granulomas from sarcoidosis patients with the use of immunohistochemistry. RESULTS: The HLA-G*010102/-G*0106 alleles were observed more often in sarcoidosis patients (39.4%) than in controls (26.4%), p = 0.025 (Fisher's exact test); however, not significant after correction (p(c) = 0.15). When HLA-G expression was investigated by immunohistochemistry in granulomas from sarcoidosis patients, weak HLA-G expression was observed in only one patient. CONCLUSIONS: HLA-G alleles that include a 14-bp sequence polymorphism in exon 8 of the HLA-G gene are observed more often in sarcoidosis patients than in controls. The sequence variation may influence HLA-G mRNA stability and influence the expression of soluble isoforms of HLA-G. Only rare and weak expression of HLA-G was observed in granulomas from sarcoidosis patients. More studies are needed to further elucidate the possible role for HLA-G in sarcoidosis.     

Tumor infiltrating lymphocytes in seminoma lesions comprise clonally expanded cytotoxic T cells

Seminoma lesions are characterized by a brisk inflammatory infiltrate containing both CD4 and CD8 T cells, which is of prognostic significance. However, whether seminoma cells express the HLA molecules required for classical T-cell recognition remains controversial. In the present study, we conducted a molecular, phenotypical and functional characterization of tumor infiltrating lymphocytes (TILs) from seminoma lesions. T-cell receptor clonotype mapping demonstrated the presence of clonally expanded T cells in the majority of the lesions. The cytotoxic capacity of TILs was indicated by expression of CD107a, which is a recently described surrogate marker for cytolytic activity. Indeed, the frequency of CD107a positive cells was substantially higher in TILs when compared to peripheral blood mononuclear cells. Moreover, fluorescence activated cell sorting of CD107a positive TILs allowed comparison of the clonotypic T-cell receptor fingerprint and demonstrated the ability of expanded clones to express this cytotoxic marker, suggesting cytotoxic activity at the tumor site. The cytotoxicity was confirmed by in situ granzyme B expression. Furthermore, by staining with multimeric HLA-peptide complexes, we could demonstrate the presence of Mage-3 specific T cells among TILs. In summary, specific and functional T-cell responses are operative in seminoma, indicating that the inflammatory infiltrate is indeed involved in the immunological control of the tumor.     

Congenital myasthenic syndromes: progress over the past decade

Congenital myasthenic syndromes (CMS) stem from defects in presynaptic, synaptic basal lamina, and postsynaptic proteins. The presynaptic CMS are associated with defects that curtail the evoked release of acetylcholine (ACh) quanta or ACh resynthesis. Defects in ACh resynthesis have now been traced to mutations in choline acetyltransferase. A basal lamina CMS is caused by mutations in the collagenic tail subunit (ColQ) of the endplate species of acetylcholinesterase that prevent the tail subunit from associating with catalytic subunits or from becoming inserted into the synaptic basal lamina. Most postsynaptic CMS are caused by mutations in subunits of the acetylcholine receptor (AChR) that alter the kinetic properties or decrease the expression of AChR. The kinetic mutations increase or decrease the synaptic response to ACh and result in slow- and fast-channel syndromes, respectively. Most low-expressor mutations reside in the AChR epsilon subunit and are partially compensated by residual expression of the fetal type gamma subunit. In a subset of CMS patients, endplate AChR deficiency is caused by mutations in rapsyn, a molecule that plays a critical role in concentrating AChR in the postsynaptic membrane.     

Persistence of survivin specific T cells for seven years in a melanoma patient during complete remission

Monitoring and evaluation of biological responses induced by immunotherapy may provide important information with regards to efficacy, side effects, and potential improvements of treatment. Herein, we describe results from monitoring of T cell reactivity against survivin derived peptides, in a melanoma patient in complete remission following IL-2 based immunotherapy. The patient remains in complete remission five years after completion of therapy. Long-time persistence of anti-tumor responses is rarely monitored, however, in the present patient longitudinal examination of anti-survivin reactivity exceeded seven years. Throughout, survivin reactivity was monitored both by INFgamma-ELISPOT as well as by flow cytometry using HLA-multimers. Survivin specific T cell reactivity was found at all time points examined over the 7-year period. Moreover, using these two methods, similar precursor frequencies was found indicating that the majority of the survivin specific T cells posses functional capabilities. Our data demonstrate that anti-survivin T cells may persist in the periphery for extended periods in the absence of clinical manifestation of disease as well as autoimmunity.     

Immunoelectrophoretic studies on human small intestinal brush border proteins--amount of lactase protein in adult-type hypolactasia

Jejunal biopsies from 15 Greenlandic and three Danish patients with adult type hypolactasia and nine Greenlandic and 15 Danish patients with normal lactase activity were analysed quantitatively for lactase protein by crossed immunoelectrophoresis. A constant correlation between the amount of lactase activity and immunologically reactive lactase protein was demonstrated irrespective of the lactase activity level. As immunoelectrophoresis expresses the amount of enzyme protein independent of the enzymatic activity, it is concluded that the low enzymatic activity in adults with hypolactasia is caused by a low amount of lactase and not by a modified inactive enzyme.