Monika Maria Welle

Development, significance, and heterogeneity of mast cells with particular regard to the mast cell-specific proteases chymase and tryptase.

Mast cells are one of the major effector cells in the pathogenesis of the immediate‐type hypersensitivity reaction in a number of non‐allergic immune disorders as well as in normal physiological processes. In addition, it has been shown recently that mast cells also play a significant role in a life‐saving host response to bacterial reactions. But as much as the immunopathological role of mast cells has been acknowledged, these cells have also aroused much controversy and confusion. By now it is clear that one explanation for the sometimes even contradictory opinions on mast cell function arise from mast cell heterogeneity. This heterogeneity can express itself as differences in histochemical, biochemical, and functional characteristics. In vitro systems provided a powerful tool for the investigation of the basic mechanisms for mast cell development and differentiation and helped to demonstrate that mast cell heterogeneity can be traced back to certain cytokine patterns that are present in different microenvironments. In this context it has also been shown that the growth factors required for human mast cell differentiation are somewhat different than those for rodents. In rodents, the atypical, T cell‐dependent mucosal type mast cell can be distinguished from the T cell‐independent connective tissue‐type mast cell. In humans, the strict classification into mucosal and connective tissue‐type mast cells is not possible and the content of mast cell‐specific proteases chymase and tryptase is the main criterion for mast cell subtypes in humans. The large quantities of tryptase and chymase that are synthesized by mast cells suggest and emphasize the significance of these proteinases in mast cell function and stimulate d investigations about the biological properties of these mast cell‐specific proteases. Comparing their biological activities it becomes clear that they share some activities. On the other hand, tryptase seems to participate in proinflammatory mast cell function, whereas chymase seems to be more involved in inflammatory reactions. This review provides a short overview of the discovery, origin, development, and biological significance of mast cells and will then concentrate on mast cell heterogeneity in rodents and humans with respect to the mast cell proteases tryptase and chymase and their function. J. Leukoc. Biol. 61: 233–245; 1997.

Canine mast cell tumours: a review of the pathogenesis, clinical features, pathology and treatment

Mast cells (MCs) are well known for their neoplastic transformation in solitary and multiple cutaneous mast cell tumours (MCTs), as well as visceral and systemic mastocytosis. Dogs have a unique risk of developing cutaneous MCTs, and they account for 7% to 21% of all canine skin tumours. The aetiology of canine MCTs is unknown but is probably multifactorial. This article reviews up-to-date knowledge on the pathogenesis, the clinical presentation, the clinical prognostic factors, the diagnostic workup including clinical staging, cytological findings, histological findings and the various grading systems which have been evaluated based on morphology, the assessment of proliferation markers and other factors such as vessel density. Furthermore, detailed information about current treatment protocols for canine cutaneous MCTs is provided.

PCR-based detection of canine Leishmania infections in formalin-fixed and paraffin-embedded skin biopsies: elaboration of a protocol for quality assessment of the diagnostic amplification reaction.

Diagnosis of the cutaneous form of canine leishmaniosis is mostly performed by histological or immunohistological examination of skin biopsies. In modern histology, the polymerase chain reaction (PCR) has gained increasing importance as a complementary tool to directly demonstrate the presence of parasite DNA in the tissue sections. For the present study, a previously described Leishmania-PCR has been further developed and optimised in view of its practicability for routine histological application. Since formalin-fixation of histological specimens causes partial DNA-destruction, which may hamper diagnostic PCR analysis, primers specific for the highly conserved alpha-actin gene sequences were used to pre-diagnostically assess the isolated sample-DNA for its functionality in a PCR-reaction. This alpha-actin-specific PCR detects DNA from a large variety of mammalian species and thus exhibits relevance for both human and veterinary medical application. A recombinant internal positive control was introduced to monitor possible sample-related inhibitory effects during the amplification reaction. We performed a retrospective evaluative study with 18 formalin-fixed samples from dogs with suspected or proven leishmaniosis. Six samples were PCR-incompatible. In turn, 9 of the other 12 samples were PCR-positive, and immunohistochemical results matched these findings. Based on these technical achievements, the Leishmania-PCR proved to be a valuable tool to complement conventional histological and immunohistological methods for diagnosis of cutaneous leishmaniosis in formalin-fixed, paraffin-embedded skin biopsies.

Interleukin-6-Deficient Mice Are Highly Susceptible to Giardia lamblia Infection but Exhibit Normal Intestinal Immunoglobulin A Responses against the Parasite

ABSTRACT In the present study, interleukin-6 (IL-6)-deficient mice were infected with Giardia lamblia clone GS/M-83-H7. Murine IL-6 deficiency did not affect the synthesis of parasite-specific intestinal immunoglobulin A. However, in contrast to wild-type mice, IL-6-deficient animals were not able to control the acute phase of parasite infection. Reverse transcription-PCR-based quantitation of cytokine mRNA levels in peripheral lymph node cells exhibited a short-term up-regulation of IL-4 expression in IL-6-deficient mice that seemed to be associated with failure in controlling the parasite population. This observation suggests a further elucidation of IL-4-dependent, Th2-type regulatory processes regarding their potential to influence the course of G. lamblia infection in the experimental murine host.

Cutaneous Leishmaniasis in Naturally Infected Dogs is Associated with a T Helper-2-biased Immune Response

Skin lesions are a frequent manifestation of Leishmania infantum infections in Mediterranean countries. This study demonstrates by real-time reverse transcriptase-polymerase chain reaction the local cytokine response in skin biopsies from Leishmania-infected dogs (n = 10). As controls, we investigated skin biopsies from healthy (n = 10) and fleabite hypersensitive dogs (n = 10). We established a quantitative PCR to determine the parasite burden in biopsies. The objective was to elucidate whether a correlation exists between parasite number, histologic response, and T helper-1 (TH1)/T helper-2 (TH2) cytokine expression in lesional skin of naturally infected dogs. In Leishmania-infected dogs, interleukin-4 (IL-4), tumor necrosis factor α (TNF-α) and interferon-γ (IFN-γ) messenger RNA production was significantly higher than controls. Furthermore, dogs with a high Leishmania burden had a significantly higher IL-4 expression, whereas no difference was noted with regard to expression of other cytokines. By comparing the pattern of inflammation and cytokine expression, a clear trend became evident in that levels of IL-4, TNF-α, and IFN-γ were elevated in biopsies with a periadnexal nodular pattern and in biopsies where the severity of the periadnexal infiltrate was equal to the perivascular to interstitial infiltrate. Expression of IL-4, IL-13, and TNF-α was slightly increased in biopsies where plasma cells prevailed on lymphocytes, whereas expression of IFN-γ was moderately higher when lymphocytes were predominating. In summary, the present study demonstrates that the local immune response in naturally occurring leishmaniasis includes TH1 as well as TH2 cytokine subsets. Furthermore, respective data suggest that increased expression of the TH2-type cytokine IL-4 is associated with both severe clinical signs and a high parasite burden in the skin lesions.

Occurrence of Leishmania sp. in cutaneous lesions of horses in Central Europe

The present report describes a novel etiological agent of cutaneous leishmaniasis in horses that, at least for some cases, sporadically appeared as autochthonous infections in geographically distant regions of Germany and Switzerland. The infection was initially diagnosed upon clinical and immunohistological findings. Subsequent comparative sequence analysis of diagnostic PCR products from the internal transcribed spacer 1 (ITS1) of ssrRNA classified the respective isolates as neither Old World nor New World Leishmania species. However, four isolates subjected to molecular analyses all exhibited a close phylogenetic relationship to Leishmania sp. siamensis, an organism recently identified in a visceral leishmaniasis patient from Thailand. Future investigations will demonstrate if this form of leishmaniasis represents an emerging, and perhaps zoonotic, disease of European, or even global, importance.

Immunoglobulin-E-bearing cells in skin biopsies of horses with insect bite hypersensitivity

The aim of the present study was to investigate, with immunohistochemistry and in situ hybridisation, if immunoglobulin-E (IgE) and mast cells are involved in the pathogenesis of insect bite hypersensitivity (IBH), an allergic dermatitis of horses. In tissue sections fixed in paraformaldehyde (PFA) for <24 h, significantly more IgE protein-bearing cells were found in the dermis and epidermis of acute and chronic IBH lesions than in skin biopsies from healthy horses (medians = 466, 236 and 110 cells/mm2, respectively; P < or = 0.01). More IgE-mRNA positive (+) cells were observed in the dermis of acute IBH lesions than in the dermis of healthy skin (median = 2.8 vs. 0.0 cells/mm2; P < or = 0.01). Significantly, more mast cells were detected with metachromatic (median = 160 vs. 62 cells/mm2; P < or = 0.001) and tryptase-specific stainings (median = 120 vs. 69 cells/mm2; P < or = 0.001) in the dermis of acute IBH biopsies compared to healthy skin. No chymase+ mast cells were found in any skin biopsy. IBH lesions fixed in PFA for >24 h were compared to dermatomycosis (DM) lesions; IBH biopsies contained a similar number of IgE-protein+ cells to DM biopsies (median = 249 vs. 192 cells/mm2; P = 0.08) but had significantly more IgE-mRNA+, metachromatic and tryptase+ mast cells than DM biopsies. This study suggests an involvement of IgE-mediated immune reactions in the pathogenesis of IBH as well as, sometimes, in dermatomycosis. Using double labelling, cells which expressed IgE protein and contained mast cell enzymes were detected.

Two cases of feline leishmaniosis in Switzerland

Two cats with Leishmania species infections were investigated. The first had been imported from Spain with a non-healing, ulcerated nodule on a hindleg. The presence of Leishmania species was detected by histopathology and PCR on samples of skin. The lesion was unresponsive to treatment with allopurinol for three months but the cat was treated successfully by removing the lesion surgically. The second cat had lived in both Spain and Switzerland, and had a history of recurrent skin lesions on its head and neck. A diagnosis of pemphigus foliaceus was made on the basis of histopathology, but Leishmania species serology (ELISA) and PCR of skin were positive, leading to a diagnosis of a Leishmania species infection combined with pemphigus foliaceus.

The keratinocyte in epidermal renewal and defence

Traditionally, keratinocytes have been considered inert constituents of the multilayered epidermis. Todays understanding has fundamentally changed. The keratinocyte is now recognized as an active player in epidermal renewal with key functions in the skins immune defence. Under homeostatic conditions, keratinocyte progenitor cells are believed to divide symmetrically or asymmetrically, that is they continue to proliferate or go on to terminally differentiate and build up the overlaying epidermis. The fine-tuned process of epidermal renewal relies on an extraordinary network of signalling cascades which are governed by keratinocyte-receptor interactions with the environment through paracrine and autocrine circuits. Opposing this coordinated homeostatic process are signals of wounding and inflammation. They alter the fate of the keratinocyte and its response to the environment through changes in adhesion molecules and surface receptors, in addition to triggering an immediate inflammatory keratinocyte response in terms of secretion of cytokines, chemokines and antimicrobial peptides. If uncontrolled, the fundamental changes imposed by wounding and inflammation upon the homeostatic programme can lead to severe skin lesions including chronic inflammatory disorders. This review will describe the current knowledge of the regulatory signalling network which allows the keratinocyte to actively impact both epidermal homeostasis and the inflammatory response.

Keratinocyte biology and pathology

It is the saying of Socrates, ‘I know that I know nothing’, that comes to mind when reading through our review article from 1997. We realize how limited our knowledge on the biology and pathology of the epidermis was at the time and how much it has evolved since then. In our review, we had focused on the epidermis as a structural membrane protecting inner homeostasis. We also knew and had emphasized how the keratinocyte that forms this structure undergoes a highly orchestrated process of proliferation and differentiation through differential expression of structural proteins, surface molecules and enzymes. In recent years, it has become evident that the epidermis is a complex multicellular organ, in which a sophisticated crosstalk between its cells, the environment and the body’s metabolism takes place to ensure its many essential functions. While the air–liquid and the liquid–liquid barriers of the epidermis (Figure 1) form potent measures for separating the inside from the outside milieu, epidermal keratinocytes also have an immunostimulatory role to build up the defence system in co-operation with epidermal immune cells. The epidermis is, however, not just a protective measure against harmful external influences and maintenance of the inner