Correspondence

Investigation of epidermotropism in canine mycosis fungoides: expression of intercellular adhesion molecule-1 (ICAM-1) and beta-2 integrins

In human mycosis fungoides (MF), interactions between LFA-1 (CD11a/CD18) and ICAM-1 (CD54) are involved in lymphocyte adhesion to keratinocytes. The purpose of this study was to evaluate the expression of ICAM-1, beta-2 integrins and class II major histocompatibility complex molecules (MHC II) on keratinocytes and infiltrating lymphocytes in canine MF. Sections of frozen skin biopsy specimens from normal dogs (n = 3) and dogs with MF (n = 17) were evaluated by immunohistochemistry for expression of ICAM-1, beta-2 integrins, and class II MHC molecules. Our results demonstrated that in canine MF, ICAM-1 was expressed variably on epidermal and follicular keratinocytes. The extent of keratinocyte ICAM-1 expression did not correlate with the degree of lymphocyte epithelial infiltration, nor with lymphocyte LFA-1 expression. This was especially evident in cases of Pagetoid reticulosis-like disease in which prominent lymphocyte epidermotropism was not accompanied by keratinocyte ICAM-1 expression. Keratinocyte class II MHC molecule expression did not correlate with keratinocyte ICAM-1 expression. In conclusion, in canine MF, the lack of statistically significant correlations between epithelial lymphocyte infiltration and keratinocyte ICAM-1 expression, and between keratinocyte ICAM-1 and lymphocyte LFA-1 staining, suggests that the LFA-1/ICAM-1 pathway is not the major adhesion mechanism between lymphocytes and keratinocytes. It is suspected that different ligands of the LFA-1 integrin (e.g. ICAM-2) or other adhesion molecules (e.g. CD2/LFA-3, VLA-1) might be involved in the epitheliotropism phenomenon in canine MF. These hypothesis cannot be evaluated in the dog at this time owing to the lack of specific monoclonal antibodies.

Epitope mapping of CD1a, CD1b, and CD1c antigens in human skin: differential localization on Langerhans cells, keratinocytes, and basement membrane zone

CD1 antigens are classified into at least three groups, CD1a, CD1b, and CD1c. In order to delineate the localization of epitopes of CD1 antigens in human skin, we examined the immunoreactivity of fourteen different CD1 antibodies (seven CD1a, five CD1b, and two CD1c antibodies). The epitopes for CD1a, CD1b, and CD1c are differentially localized on epidermal Langerhans cells, dermal dendritic cells, keratinocytes, the luminal portion of eccrine gland ducts, and the basement membrane zone in normal human skin.

Epitopes for CD1a, CD1b, and CD1c antigens are differentially mapped on Langerhans cells, dermal dendritic cells, keratinocytes, and basement membrane zone in human skin

BACKGROUND

CD1 antigens are classified serologically into at least three groups, CD1a, CD1b, and CD1c, and many kinds of monoclonal antibodies are available for each subgroup of CD1 antigens. CD1a, CD1b, and CD1c antigens have been shown to be selectively and differentially expressed on epidermal Langerhans cells and dermal dendritic cells in normal human skin.

OBJECTIVE

The objective was to further delineate the localization of epitopes of CD1 antigens in human skin.

METHODS

We examined the immunoreactivity of 14 different CD1 antibodies (seven CD1a, five CD1b, and two CD1c antibodies) with the immunoperoxidase technique. We also studied the reactivity of NU-T2 (CD1b) antibody by immunogold electron microscopy.

RESULTS

The epitopes for CD1a, CD1b, and CD1c antigens were differentially mapped on epidermal Langerhans cells, dermal dendritic cells, keratinocytes, the luminal portion of eccrine gland ducts, and the basement membrane zone in human skin.

CONCLUSION

These CD1 antibodies may be useful to analyze the phenotypic alteration of immune and nonimmune cells in various skin diseases.

Electron microscopy of epidermal and dermal Langerhans' cells in long-lasting allergy patch tests

In rare cases, normal allergy patch tests persist for weeks or months. Here, seven biopsies from six patients with long-lasting allergy patch tests, taken 15-75 days after allergen challenge, were analysed by transmission electron microscopy. In accordance with clinical expression of the test site, fine structural evidence of persistent activity of immunocompetent cells in the epidermis and dermis was observed. Moderate numbers of exocytic lymphocytes and macrophages were seen in the epidermis. Langerhans' cells (LC) appeared active, and LCs with Birbeck granules were detected both in the epidermis and the dermis and were also seen to cross the dermoepidermal junction. LC-mononuclear cell contacts were more frequent in the epidermis than is normal in allergy patch tests. A strong infiltrate of lymphocytes, macrophages, fibroblasts, mast cells, and cells resembling LCs but devoid of Birbeck granules, i.e. indeterminate cells, was seen in the upper dermis. Less than 10% of the dermal cells showing the fine structural appearance of LCs had Birbeck granules, as seen in a single section. Both indeterminate cells and LCs were apposed by lymphocytes in the dermis, often in a rosette-like fashion. The present paper is descriptive but gives background to the understanding of events in long-lasting allergy patch tests. However, the reason for and the basic mechanisms of long-lasting allergy patch tests are not known. A defect in down-regulation of the contact hypersensitivity reaction and/or a constant antigen stimulation could be responsible for the persistence of these allergy patch test reactions.