American cutaneous leishmaniasis is characterized by a spectrum of clinical manifestations. These include localized, often self-healing single lesions, intermediate forms which frequently produce mucosal lesions and often show exaggerated delayed-type hypersensitivity (DTH), and the rare diffuse cutaneous leishmaniasis in which no reaction of protective cell-mediated immunity or DTH can be demonstrated. Clinical, pathological and immunological studies have begun to unravel some of the mechanisms associated with different disease manifestations, dependent on complex interactions between the host immune response, measured in terms of indices including lymphocyte subsets and lymphokines in vitro and within active lesions, and different species of Leishmania.
Accessory signals, which include adhesion molecules, MHC-II molecules and cytokines, are necessary to foster the interaction between memory T cells and epidermal cells, that is required to promote cutaneous inflammatory responses. American cutaneous leishmaniasis (ACL) is characterized by a spectrum of immunological manifestations, and is a prototype disease for the study of regulatory mechanisms involved in immune protection against protozoal infection. In the present study, we show that diffuse cutaneous leishmaniasis (DCL) epidermis contains keratinocytes that do not express ICAM-1 and HLA-DR molecules. Langerhans cells (LC) are within normal values or somewhat lower, and a very few cells expressing the HB15 molecule--a new described member of the Ig superfamily--are found in such lesions. Mucocutaneous leishmaniasis (MCL) epithelium shows an increased expression of ICAM-1 and HLA-DR molecules, few HB15+ cells, and an absence of epithelial LC. Localized cutaneous leishmaniasis (LCL) epidermis displays ICAM-1+ keratinocytes organized in patches, a uniform expression of HLA-DR, hyperplasia of LC, and numerous HB15+ cells. In all forms of the disease, infiltrating T cells express more LFA-1 beta than LFA-1 alpha, but LFA-1 beta+ T cells are more abundant in LCL granulomas. In contrast, there are more LFA-1 alpha+ T cells in DCL and MCL than in LCL granulomas. LCL lesions also show the highest numbers of HB15+ cells within the granuloma. These results indicate the importance of adhesion molecules in ACL lesions, and open new possibilities for therapeutic schemes oriented towards the control of cell migration.
We report a case of Plasmodium vivax infection manifested as severe thrombocytopenia, bilateral hydronephrosis, and hypotension in a returning traveler from a malaria-endemic area in Venezuela. While most of the efforts to prevent malaria in travelers focus on the life-threatening consequences of Plasmodium falciparum malaria, nonimmune travelers who encounter infection with P vivax may also develop serious complications. This case highlights the importance of preventing malaria cases among nonimmune or semi-immune individuals traveling to P vivax-endemic areas.
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