Expression of inducible nitric oxide synthase in skin lesions of patients with american cutaneous leishmaniasis

Abstract

Cytokine-inducible (or type 2) nitric oxide synthase (iNOS) is indispensable for the resolution of Leishmania major or Leishmania donovani infections in mice. In contrast, little is known about the expression and function of iNOS in human leishmaniasis. Here, we show by immunohistological analysis of skin biopsies from Mexican patients with local (LCL) or diffuse (DCL) cutaneous leishmaniasis that the expression of iNOS was most prominent in LCL lesions with small numbers of parasites whereas lesions with a high parasite burden (LCL or DCL) contained considerably fewer iNOS-positive cells. This is the first study to suggest an antileishmanial function of iNOS in human Leishmania infections in vivo.

FIG. 1.

Immunoperoxidase staining of skin lesions from patients with LCL (A to D) or DCL (E to H) for L. mexicana parasites (panels A and E), macrophages (panels B and F), T cells (panels C and G), and iNOS (panels D and H). Magnifications: panels A to C and E to G, ×200; panels D and H, ×400; insets, ×1,000. Note that in the sections from LCL, there were only a few parasites compared to the DCL sections (cf. panels A and E), whereas the intensity and the frequency of the iNOS staining was much more prominent in the former than in the latter (cf. panels D and H) (panel H shows one of the strongest iNOS stainings obtained in a DCL lesion).