Abstract:
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In this study biopsies from skin lesions and draining lymph nodes of patients suffering from
cutaneous leishmaniasis caused by Leishmania major were examined by immunohistochemistry,
and by light and electron microscopy to identify the types of antigen-presenting cells (APC) and
their location. APC, identified morphologically and by their expression of specific cell markers,
included Langerhans cells, macrophages, follicular dendritic cells, and interdigitating reticulum
cells of the paracortex of lymph nodes. These cells expressed MHC class II antigens and contained
Leishmania antigen. Since some keratinocytes and endothelial cells also showed these characteristics,
they may also act as APC. By examining tissue samples from skin lesions and draining lymph
nodes it was possible to follow the probable route of trafficking of various inflammatory cells
between the skin lesion and lymph nodes. Leishmania antigen containing Langerhans cells were
found in the epidermis, dermis and the regional lymph nodes. We believe these cells translocate
from the epidermis to the dermis, where they take up antigen and migrate to the paracortex of the
regional lymph nodes. There they are intimately associated with cells of the paracortex, and could
be involved in the generation of Leishmania-specific T memory cells. LFA-l-positive T cells of the
CD45RO phenotype were found in the skin lesion. Venular endothelium in the skin lesions
expressed intercellular adhesion molecule-I (ICAM-1), which is the ligand for LFA-1. The
migration of lymphocytes from the vascular lumen to the site of inflammation is possibly a
result of the interaction of these two adhesion molecules. |