Intermediate or chronic cutaneous leishmaniasis: leukocyte immunophenotypes and cytokine characterisation of the lesion

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Abstract
The American cutaneous forms of leishmaniasis include immune‐responder individuals with localised cutaneous leishmaniasis (LCL) and non‐responder individuals with diffuse cutaneous leishmaniasis (DCL). Patients with intermediate or chronic cutaneous leishmaniasis (ICL) have increased morbidity due to the length of their illness, atypical forms and areas of compromise. In the present study, we evaluated the expression of the leukocyte antigens (CD4, CD8, CLA: cutaneous lymphocyte antigen, CD69, CD83 and CD1a) and cytokines (IFN‐γ, IL‐4, IL‐10 and TGF‐β1) in the lesions of patients with ICL (n = 18) using an immunocytochemical procedure. ICL results were compared with the information for LCL (n = 19) and DCL (n = 4). The numbers of CD4+ and CD8+ T cells in ICL were similar to those of LCL lesions, but significantly different (P ≤ 0.05) from DCL lesions. LCL lesions have about half the numbers of early activated CD69+ cells as ICL, but most are CLA+ skin homing memory T cells, whereas ICL lesions have the highest number of CD69+ T cells, but about one‐third of these cells expressed CLA. This suggests that the granuloma of ICL patients contains many activated T cells that are unprimed to cutaneous‐launched antigens, thus contributing to an aberrant immune response. In contrast, DCL granulomas presented the lowest numbers of activated CD69+ and CLA+ cells, associated with the characteristic tolerogenic state of these patients. The immunolocalisation of cytokines showed a mixed cytokine pattern in ICL lesions with many positive cells for IL‐10, TGF‐β1, IL‐4 and IFN‐γ, with a preponderance of the first two, and different from the prevalent Th1 and Th2 responses associated with LCL and DCL lesions, respectively. CD1a+ Langerhans cells were decreased (P ≤ 0.05) in both ICL (271 ± 15 cells/mm2) and DCL (245 ± 19 cells/mm2) as compared to LCL (527 ± 54 cells/mm2) epidermis. The percentage of IL‐10+ epidermal Langerhans cells in ICL (33.69), from the total CD1a+ population, was higher than in LCL (17.45). In addition, fewer CD83+ primed Langerhans cells were present in ICL epidermis. The diminished participation of epidermal Langerhans cells, causing a defective signalling by the epidermis, in ICL lesions may account for the tissue‐damaging state observed in these patients.