Whey filtration: a review of products, application, and pretreatment with transglutaminase enzyme.

In the cheese industry, whey, which is rich in lactose and proteins, is underutilized, causing adverse environmental impacts. The fractionation of its components, typically carried out through filtration membranes, faces operational challenges such as membrane fouling, significant protein loss during the process, and extended operating times. These challenges require attention and specific methods for optimization and to increase efficiency. A promising strategy to enhance industry efficiency and sustainability is the use of enzymatic pre-treatment with the enzyme transglutaminase (TGase). This enzyme plays a crucial role in protein modification, catalyzing covalent cross-links between lysine and glutamine residues, increasing the molecular weight of proteins, facilitating their retention on membranes, and contributing to the improvement of the quality of the final products. The aim of this study is to review the application of the enzyme TGase as a pretreatment in whey protein filtration. The scope involves assessing the enzyme's impact on whey protein properties and its relationship with process performance. It also aims to identify both the optimization of operational parameters and the enhancement of product characteristics. This study demonstrates that the application of TGase leads to improved performance in protein concentration, lactose permeation, and permeate flux rate during the filtration process. It also has the capacity to enhance protein solubility, viscosity, thermal stability, and protein gelation in whey. In this context, it is relevant for enhancing the characteristics of whey, thereby contributing to the production of higher quality final products in the food industry. © 2023 Society of Chemical Industry.

Collagen VII maintains proteostasis in dermal fibroblasts by scaffolding TANGO1 cargo.

Lack of type VII collagen (C7) disrupts cellular proteostasis yet the mechanism remains undescribed. By studying the relationship between C7 and the extracellular matrix (ECM)-associated proteins thrombospondin-1 (TSP1), type XII collagen (C12) and tissue transglutaminase (TGM2) in primary human dermal fibroblasts from multiple donors with or without the genetic disease recessive dystrophic epidermolysis bullosa (RDEB) (n=31), we demonstrate that secretion of each of these proteins is increased in the presence of C7. In dermal fibroblasts isolated from patients with RDEB, where C7 is absent or defective, association with the COPII outer coat protein SEC31 and ultimately secretion of each of these ECM-associated proteins is reduced and intracellular levels are increased. In RDEB fibroblasts, overall collagen secretion (as determined by the levels of hydroxyproline in the media) is unchanged while traffic from the ER to Golgi of TSP1, C12 and TGM2 occurs in a type I collagen (C1) dependent manner. In normal fibroblasts association of TSP1, C12 and TGM2 with the ER exit site transmembrane protein Transport ANd Golgi Organization-1 (TANGO1) as determined by proximity ligation assays, requires C7. In the absence of wild-type C7, or when ECM-associated proteins are overexpressed, C1 proximity and intracellular levels increase resulting in elevated cellular stress responses and elevated TGFß signaling. Collectively, these data demonstrate a role for C7 in loading COPII vesicle cargo and provides a mechanism for disrupted proteostasis, elevated cellular stress and increased TGFß signaling in patients with RDEB. Furthermore, our data point to a threshold of cargo loading that can be exceeded with increased protein levels leading to pathological outcomes in otherwise normal cells.

Evaluation of nuclear NF-κB, transglutaminase2, and ERCC1 as predictors of platinum resistance in testicular tumors

ABSTRACT Purpose: Testicular germ cells tumor (TGCT) are associated with a high cure rate and are treated with platinum-based chemotherapy. However, a group of testicular cancer patients may have a very unfavorable evolution and insensitivity to the main therapeutic agent chemotherapy (CT) cisplatin. The aim of this study was to evaluate the risk of recurrence and overall survival related to the expression of nuclear factor kappa-B (NF-κB), transglutaminase 2 (TG2) and excision repair cross-complementation group 1 (ERCC1) in patients with TGCT treated with platinum combinations. Patients and Methods: A retrospective study was performed with TGCT patients treated with platinum-based chemotherapy. Immunohistochemical analysis was performed and the expression was correlated with clinical and laboratory data. Results: Fifty patients were included, the mean age was 28.4 years (18 to 45), and 76% were non-seminoma. All patients were treated with standard cisplatin, etoposide and bleomycin or cisplatin, and etoposide. Patient's analyzed immunodetection for NF-κB, TG2, and ERCC1 were positive in 76%, 54% and 42%, respectively. Multivariate analysis identified that positive expressions to ERCC1 and NF-κB are independent risk factors for higher recurrence TGCT after chemotherapy (RR 2.96 and 3.16, respectively). Patients with positive expression of ERCC1 presented a poor overall survival rate for 10-year follow (p=0.001). Conclusions: The expression of ERCC1 and NF-κB give a worse prognosis for relapse, and only ERCC1 had an influence on the overall survival of TGCT patients treated with platinum-based chemotherapy. These may represent markers that predict poor clinical outcome and response to cisplatin.

Evaluation of nuclear NF-κB, transglutaminase2, and ERCC1 as predictors of platinum resistance in testicular tumors.

PURPOSE: Testicular germ cells tumor (TGCT) are associated with a high cure rate and are treated with platinum-based chemotherapy. However, a group of testicular cancer patients may have a very unfavorable evolution and insensitivity to the main therapeutic agent chemotherapy (CT) cisplatin. The aim of this study was to evaluate the risk of recurrence and overall survival related to the expression of nuclear factor kappa-B (NF-κB), transglutaminase 2 (TG2) and excision repair cross-complementation group 1 (ERCC1) in patients with TGCT treated with platinum combinations. PATIENTS AND METHODS: A retrospective study was performed with TGCT patients treated with platinum-based chemotherapy. Immunohistochemical analysis was performed and the expression was correlated with clinical and laboratory data. RESULTS: Fifty patients were included, the mean age was 28.4 years (18 to 45), and 76% were non-seminoma. All patients were treated with standard cisplatin, etoposide and bleomycin or cisplatin, and etoposide. Patient's analyzed immunodetection for NF-κB, TG2, and ERCC1 were positive in 76%, 54% and 42%, respectively. Multivariate analysis identified that positive expressions to ERCC1 and NF-κB are independent risk factors for higher recurrence TGCT after chemotherapy (RR 2.96 and 3.16, respectively). Patients with positive expression of ERCC1 presented a poor overall survival rate for 10-year follow (p=0.001). CONCLUSIONS: The expression of ERCC1 and NF-κB give a worse prognosis for relapse, and only ERCC1 had an influence on the overall survival of TGCT patients treated with platinum-based chemotherapy. These may represent markers that predict poor clinical outcome and response to cisplatin.

Transglutaminases: part I-origins, sources, and biotechnological characteristics.

The transglutaminases form a large family of intracellular and extracellular enzymes that catalyze cross-links between protein molecules. Transglutaminases crosslinking properties are widely applied to various industrial processes, to improve the firmness, viscosity, elasticity, and water-holding capacity of products in the food and pharmaceutical industries. However, the extremely high costs of obtaining transglutaminases from animal sources have prompted scientists to search for new sources of these enzymes. Therefore, research has been focused on producing transglutaminases by microorganisms, which may present wider scope of use, based on enzyme-specific characteristics. In this review, we present an overview of the literature addressing the origins, types, reactions, and general characterizations of this important enzyme family. A second review will deal with transglutaminases applications in the area of food industry, medicine, pharmaceuticals and biomaterials, as well as applications in the textile and leather industries.

The effect of enzymatic crosslinking on the viability of probiotic bacteria (Lactobacillus acidophilus) encapsulated by complex coacervation.

Lactobacillus acidophilus were encapsulated by complex coacervation followed by transglutaminase crosslinking, aiming to improve the resistance of the microcapsules and improve the protection for probiotics. Subsequently, microcapsules were dried by freeze drying. The encapsulation efficiency, morphology, thermal resistance, gastrointestinal simulation and storage stability were analysed for wet and dry forms. The treatments offered high encapsulation efficiency (68.20-97.72%). Transglutaminase maintained the structure rounded, multinucleate and homogeneous distribution of probiotics in the microcapsules. In relation to the thermal resistance, in general, microencapsulation was effective in protecting and crosslinked microcapsules demonstrated greater protection for probiotics, obtaining viable cell counts of up to 10 log CFU g-1, approximately. On exposure to the simulated gastrointestinal tract, microencapsulation coupled to crosslinking demonstrated good results and the dry form was more efficient in the protection and the treatment with greater amount of transglutaminase was highlighted (9.07 log CFU g-1). As for storage, probiotic viability was maintained for up to 60 days in freezing temperature, with counts of up to 9.59 log CFU g-1. The results obtained in the present work are innovative and present a promising alternative for the protection of probiotics and their addition in food products.

Modifying Enzymes Are Elicited by ER Stress, Generating Epitopes That Are Selectively Recognized by CD4+ T Cells in Patients With Type 1 Diabetes.

In spite of tolerance mechanisms, some individuals develop T-cell-mediated autoimmunity. Posttranslational modifications that increase the affinity of epitope presentation and/or recognition represent one means through which self-tolerance mechanisms can be circumvented. We investigated T-cell recognition of peptides that correspond to modified ß-cell antigens in subjects with type 1 diabetes. Modified peptides elicited enhanced proliferation by autoreactive T-cell clones. Endoplasmic reticulum (ER) stress in insulinoma cells increased cytosolic calcium and the activity of tissue transglutaminase 2 (tTG2). Furthermore, stressed human islets and insulinomas elicited effector responses from T cells specific for modified peptides, suggesting that ER stress-derived tTG2 activity generated deamidated neoepitopes that autoreactive T cells recognized. Patients with type 1 diabetes had large numbers of T cells specific for these epitopes in their peripheral blood. T cells with these specificities were also isolated from the pancreatic draining lymph nodes of cadaveric donors with established diabetes. Together, these results suggest that self-antigens are enzymatically modified in ß-cells during ER stress, giving rise to modified epitopes that could serve to initiate autoimmunity or to further broaden the antigenic repertoire, activating potentially pathogenic CD4+ T cells that may not be effectively eliminated by negative selection.

Tissue transglutaminase on trophoblast cells as a possible target of autoantibodies contributing to pregnancy complications in celiac patients.

PROBLEM: Women with celiac disease (CD) are often affected by atypical presentations of the disease associated with reproductive disorders as a main extra-digestive complaint. Here, we analyzed if autoantibodies against tissue transglutaminase (tTG) in sera from CD patients with reproductive disorders could display direct effects through their interaction with tTG expressed on trophoblast cells and phagocytes inducing tissue damage and interfering in the clearance of trophoblast apoptotic bodies. METHOD OF STUDY: Sera from CD women with reproductive disorders were obtained, and their ability to induce apoptosis of Swan-71 (cytotrophoblast cell line) and to modulate the wound-healing and phagocytes process was tested. RESULTS: Swan-71 cells expressed tTG and CD sera displayed a significant decrease in trophoblast cell migration and a delay in injury healing on trophoblast cells, compared with those observed with control sera. Moreover, CD sera significantly reduced trophoblast cell proliferation and increased apoptosis levels in comparison with those observed in the control sera. Finally, autoantibodies against tTG interfere in the clearance of trophoblast apoptotic bodies through a mechanism involving MFG-E8 (milk fat globulin-EGF factor 8)-tTG binding. CONCLUSION: The anti-tTG antibodies might contribute to trophoblast damage and disrupt the phagocytosis process of apoptotic bodies that could promote a pro-inflammatory microenvironment.

Transamidation of gluten proteins during the bread-making process of wheat flour to produce breads with less immunoreactive gluten.

Due to an increasing incidence of celiac disease (CD) and other gluten-related disorders, different gluten-free breads have been developed using starches and additives as a substitute for gluten. Thus, patients miss not only the taste and aroma of wheat bread but also risk their sensitive intestines. Therefore, modifying gluten to avoid an immune response in CD and its application to baking is in progress. The aim of the study was to enzymatically modify gluten on wheat flour, during bread-making avoiding the use of additives, to reduce immunoreactivity, preserving its properties. Microbial transglutaminase (mTG) or chymotrypsin (ChT) was used to bind lysine or valine to gluten proteins in a model system. The best conditions were directly applied to wheat flour for bread-making with and without punching at 45 min. Subsequently, the rheological properties of the doughs, specific volume of the loaves, immunoreactive gluten content and modification of the extracted proteins were evaluated. ChT-treated breads presented a better appearance with a more homogeneous crumb, higher specific volume values (3.34-4.25 cm(3) g(-1)) and higher reactive gluten reduction (up to 71%) than the mTG-treated ones (1.23-2.66 cm(3) g(-1)) with only a 42% reactive gluten reduction. Thus, transpeptidation during bread-making is a promising technology, although it is necessary to improve the modification process to obtain the reactive gluten reduction required in breads for the treatment of CD patients and other gluten-related disorders.

Celiac disease and gyneco-obstetrics complications: can serum antibodies modulate tissue transglutaminase functions and contribute to clinical pattern?

PROBLEM: Untreated celiac disease (CD) is often associated with early miscarriages, infertility, and alterations in menstrual cycle. Tissue transglutaminase (tTG) antibodies could be involved by interfering with tTG transamidating activity and/or biological functions mediated by its interaction with fibronectin (FN). METHOD OF STUDY: The correlation between the presence of extra-digestive disorders and the reactivity of sera against tTG-FN and its effects on tTG transamidating activity was analyzed in a group or 50 women with recently diagnosed CD. RESULTS: Heterogeneous behavior was observed among serum samples derived from patients with different complaints, suggesting that differences in fine specificity patterns could condition clinical outcome. Sera from women with gynecological and/or obstetric problems induced significant inhibition of in vitro enzymatic activity in comparison with those without these kinds of disorders. CONCLUSIONS: The significant correlation observed between serum effects and clinical profile suggests a putative involvement of tTG-specific antibodies in gynecological and/or obstetric disorders during active CD.

Early increases in transglutaminase activity and polyamine levels in a Mallory-Denk body mouse model.

Rodents treated with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) are a model of two hepatic toxic manifestations: porphyria and the appearance of hepatic cytoplasmic protein aggregates (Mallory-Denk Bodies, MDBs). MDBs are induced after long-term DDC feeding, consist primarily of keratins 8 and 18, and contain glutamine-lysine cross-links generated by transglutaminases (TGs). TGs are Ca(2+)-dependent enzymes which catalyze the formation of covalent bonds between proteins and between proteins and polyamines. The aim of the current study was to investigate the time-course of TG hepatic activity in CF1 male mice either acutely or chronically treated with DDC and to correlate this activity with polyamine and porphyrin levels. On day 3 of the treatment, statistically significant increases in TG activity (75%), porphyrin content (6740%) and spermidine levels (73%) were observed. Although not statistically significant, at this time point putrescine levels showed an increase of 52%. The highest TG activity was observed on day 30 (522%), while porphyrin levels were still gradually increasing by day 45 (37,000%). From day 7 of the treatment and until the end of the experiment, putrescine levels remained increased (781%). Spermine levels were not affected by the treatment. The DDC-induced increases in putrescine and spermidine levels herein reported seem to be an early event contributing to the stimulation of liver TG activity, and thus to the promotion of cross-linking reactions between keratin proteins. This in turn would contribute to the formation of protein aggregates, which would lead to the appearance of MDBs. Due to the pro-oxidant and antioxidant properties of polyamines, it is possible to speculate that putrescine and spermidine may also participate at several levels in the oxidative stress processes associated with MDB formation.

Environmental effects on transglutaminase production and cell sporulation in submerged cultivation of Bacillus circulans.

In this research, the effects of pH, temperature, and oxygen on growth kinetics of a newly isolated strain of Bacillus circulans from the Amazon and their correlations with transglutaminase (TGase) production and cell sporulation were investigated. Statistical experimental methods were used to optimize these parameters, while induction of sporulation was achieved by oxygen culture control. Full factorial composite experimental design and response surface methodology were experimentally tested. The model showed that temperature has a positive and significant effect on TGase production (P < 0.05) while pH and temperature, associated with anoxic conditions, have a marked effect on cell sporulation which is consistently linked with TGase production. The contour plot of results showed that the best culture conditions for TGase production of B. circulans were 30 degrees C, initial pH 8.5, and the highest production was obtained in late-stationary culture phase with maximal specific enzyme activity of 655 U g(-1) of cells (0.37 U/mL). A correlation between enzyme production and cell sporulation, as mediated by oxygen culture conditions, was also demonstrated and, although demonstrated only for B. subtilis, it corroborates the molecular mechanisms involved in this process. It can be suggested that B. circulans BL32 is a strong biological system for the industrial production of TGases.

Purification and partial characterization of the plasma clotting protein from the pink shrimp Farfantepenaeus paulensis.

A clotting protein (CP) was purified from the plasma of the pink shrimp Farfantepenaeus paulensis by sequential anion-exchange chromatography. The shrimp CP was able to form stable clots in vitro in the presence of hemocyte lysate and Ca2+, suggesting that the clotting reaction is catalyzed by a Ca2+-dependent transglutaminase present in shrimp hemocytes. Dansylcadaverine was incorporated into the shrimp CP in the presence of endogenous transglutaminase (hemocyte lysate), confirming that the shrimp purified CP is the substrate for the transglutaminase enzyme. The molecular mass of the CP was determined by gel filtration to be 341 kDa and 170 kDa by SDS-PAGE under reducing conditions. These results suggest that the shrimp CP consists of two identical subunits, covalently linked by disulphide bonds. The amino acid sequence at the N-terminus was 100% identical to that of the penaeids Litopenaeus vannamei and Penaeus monodon and 66% to 80% identical to the CPs of other decapods. This is the first report of a CP characterization in an Atlantic penaeid species. Further studies, including a molecular cloning approach would enable to detect which tissues express the gene of the clotting protein. It would be also useful to understand the mechanism by which the coagulation time is delayed in shrimps under stress conditions.

Accuracy and cost-effectiveness of a new strategy to screen for celiac disease in children with Down syndrome.

OBJECTIVES: To investigate the best approach to screen for celiac disease (CD) in patients with Down syndrome (DS). STUDY DESIGN: One hundred thirty-seven children with DS were followed up longitudinally. CD screening was offered in 1994, 1996, and 1999 by determination of serum immunoglobulin A-anti-endomysium antibodies (AEA). The HLA-DQA1*0501/DQB1*02 allelic combination known to be strongly positively associated with CD was typed. All IgA-AEA-positive children were given the opportunity to undergo a small bowel biopsy: if villous atrophy was found, the diagnosis of CD was established. RESULTS: CD was diagnosed in 11 (8%) children: 8 in 1994 and 3 in 1996. All of them carried the HLA-DQ alleles associated with CD. The presence of symptoms was not useful in discriminating which children could have CD. CONCLUSIONS: Screening once in a lifetime is not enough to detect CD in patients with DS. We propose a new, accurate, and cost-sparing 2-step strategy for screening, based on selection of the individuals with potential CD by HLA-DQ typing and on longitudinal serologic CD screening in this selected group.

Factor XIIIa+ dermal dendrocytes in erythema elevatum diutinum and ordinary cutaneous leukocytoclastic vasculitis lesions.

Factor XIIIa+ dermal dendrocytes belong to the dermal microvascular unit and are related to wound healing, angiogenic and fibrogenic processes. Erythema elevatum diutinum (EED) is a leukocytoclastic vasculitis followed by repair and fibrosis. In order to verify the involvement of fXIIIa+DD in the pathogenesis of EED and ordinary leukocytoclastic vasculitis (OLV) these cells were immune labeled with anti-factor XIIIa antibody and quantified in 15 biopsies of EED, 18 of OLV and compared with 11 fragments of normal skin (NS). The number of vessels was evaluated by endothelial cell staining with anti CD34 antibody. FXIIIa+DD appeared in both groups of vasculitis with hyperthophic dendrites, with no difference in their number at any level of the dermis. The number of fXIIIa+DD in the superficial dermis was higher in OLV than in NS (p<0.001). The number of dermal vessels in the EED group was higher at all dermis depths evaluated when compared with NS (p<0.05) and in the middle and deep dermis when compared with OLV (p<0.05). The results suggest the participation of fXIIIa+DD in the immunopathological mechanisms of both groups of vasculitis studied. However, there was no correlation between the number of fXIIIa+DD and angiogenesis and fibrogenesis in the EED lesions.

Effects of aflatoxin B(1) on the liver and kidney of broiler chickens during development.

Aflatoxin B(1) (AFB(1)) negatively affects chicken (Gallus domesticus) growth. This effect is more severe during development. We studied the influence of age on the toxic effects of AFB(1) on plasma, renal and hepatic enzymes, under two protocols, in adult and in developing Arbor-Acres chickens. Protocol A: 100 male 4-week-old chickens (640 g), received AFB(1), 0.5, 1.0, or 2.0 microg/g of feed (daily p.o.), a fourth group received an aflatoxin-free diet. Five birds/group were slaughtered at 7, 14, 21 and 28 days of treatment. Body, hepatic and renal weights, succinate-dehydrogenase (SDH) and glutamate-dehydrogenase (GluDH) in plasma and liver were measured. Hepatic SDH and GluDH decreased (P<0.05). Protocol B: two groups of 24 male 1-week-old chickens (106 g) received either aflatoxin-free feed (n=24) or AFB(1) feed (2.0 microg/g). At days 7, 14, 21 and 28, the same parameters of Protocol A were measured. AFB(1) markedly reduced body weight gain (20-30%), plasma proteins, albumin, renal and hepatic protein content (P<0.05) and increased absolute and relative weights of the kidney (P<0.05). SDH and GluDH were reduced (P<0.05), while total renal gamma-glutamyltranspeptidase (GGT) increased (P<0.05). Results suggest that serum proteins, SDH and GluDH are sensitive early indicators of this toxicity that was more severe in developing chickens. Decrease in serum albumin might be used as an early and suitable indicator of the deleterious effect of this mycotoxin in developing chickens.

Increase of a calcium independent transglutaminase activity in the erythrocyte during the infection with Plasmodium falciparum.

We have studied the activity of a calcium dependent transglutaminase (EC 2.3.2.13) during the growth of the parasite Plasmodium falciparum inside the infected human erythrocyte. There is only one detectable transglutaminase in the two-cell-system, and its origin is erythrocytic. No activity was detected in preparations of the parasite devoid of erythrocyte cytoplasm. The Michaelis Menten constants (Km) of the enzyme for the substrates N'N' dimethylcaseine and putrescine were undistinguishable whether the cell extracts used in their determination were obtained from normal or from infected red cells. The total activity of transglutaminase in stringently synchronized cultures, measured at 0.5 mM Ca2+, decreased with the maturation of the parasite. However, a fraction which became irreversibly activated and independent of calcium concentration was detected. The proportion of this fraction grew with maturation; it represented only 20% of the activity in 20 hr-old-trophozoites while in 48-hr-schizonts it was more than 85% of the total activity. The activation of this fraction of transglutaminase did not depend on an increase in the erythrocyte cytoplasmic calcium, since most of the calcium was shown to be located in the parasite.

IgA antibodies to tissue transglutaminase: An effective diagnostic test for celiac disease.

OBJECTIVE: Tissue transglutaminase (tTG) is the main autoantigen recognized by endomysial antibodies. The aim of this study was to assess sensitivity, specificity, and predictive value of IgA and IgG antibodies to tTG in the diagnosis of celiac disease compared with endomysial antibodies. STUDY DESIGN: We established enzyme-linked immunosorbent assay procedures to measure IgA and IgG antibodies to tTG in sera from 48 untreated and 33 treated patients with celiac disease and from 63 patients with gastrointestinal disease who were in a control group. Sera from 10 patients with celiac disease were examined at various times after gluten was reintroduced into the patients' diet. RESULTS: Both IgA and IgG to tTG were significantly (P <.001) higher in serum of untreated patients with celiac disease versus those in the control group; IgA but not IgG was significantly (P <.001) higher in untreated versus treated patients with celiac disease. IgA and IgG antitissue tTG had a diagnostic sensitivity, specificity, and positive predictive value of 92% and 21%, 98% and 97%, and 98% and 83%, respectively. The concordance rate of IgA anti-tTG with IgA antiendomysial antibodies was 95%. In 5 of the 10 patients undergoing gluten challenge, IgA antiendomysium antibodies were detected earlier than IgA anti-tTG antibodies. CONCLUSIONS: tTG-based enzyme-linked immunosorbent assay is an effective diagnostic test, although immunofluorescent-based assays are more sensitive, particularly during gluten challenge.

Thrombomodulin expression on dermal cells in normal and psoriatic skin.

The various subsets of dermal cells with a dendritic appearance can be identified by phenotypic differences in cell markers. We report on the morphology and tissue distribution of dermal cells detected with a monoclonal antibody against thrombomodulin in histological sections of normal arm and scalp skin and psoriatic skin. Double staining with antibodies to factor XIIIa, CD34 and CD68 was also employed in scalp biopsies to elucidate the relationship between thrombomodulin+ dermal cells and dermal dendrocytes and macrophages described by others. Thrombomodulin+ dermal cells in normal arm skin had little cytoplasm with fine branched dendrites and tended to be localized just beneath the epidermis. In scalp skin these cells had longer, more numerous dendrites and were distributed in the papillae and perivascular adventitial dermis primarily in the upper and central reticular dermis. In psoriatic skin, thrombomodulin+ dermal cells had an increased cytoplasmic volume with stout, less branched dendrites and appeared in the papillae and among inflammatory cells. Dermal cells detectable by thrombomodulin expression were factor XIIIa-, CD34- and CD68-, and seemed to represent a distinct subset of dermal cells which may function in tissue repair. However, thrombomodulin+ dermal cells and factor XIIIa+ dendrocytes were frequently seen close together and could act cooperatively to regulate extravascular thrombin homeostasis in both normal and pathological dermal environments.