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The interaction of plasminogen with Leishmania mexicana promastigotes was found, using immunoperoxidase assays, to occur with a specific morphotype. In in vitro cultured promastigotes, the morphotype that possessed the plasminogen binding capacity had round to ovoid cell bodies. In contrast, neither slender nor metacyclic promastigotes showed this property. In vivo plasminogen immunofluorescence assays showed deposits of plasminogen exclusively on the cell surface of promastigotes. This was observed as intense patches spread around the cell, with higher intensities towards the flagellar pocket. Plasminogen binding capacity detected by plasmin activity increased with the age of the promastigote culture, at pH 7.2 and pH 5.5, as well as after heat shock. The total amastigote population, freshly isolated from a hamster lesion, also bound plasminogen in a lysine-dependent manner as detected by immunoperoxidase studies.

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This immunocytochemical study evaluates the presence of IgG1-4, IgA and IgE immunoglobulins in active lesions of 25 localized cutaneous leishmaniasis patients from three bioclimatic areas (Awa, Afa and Bsha) in Mérida State, Venezuela. All immunoglobulin isotypes except IgE were detected, with variable intensity, in one or more of the epidermal or dermal components of skin lesions. IgG1 and IgG2 were detected significantly more frequently than IgG3, IgG4 and IgA. The ranking of the isotypes according to frequency of detection was the same in all areas: IgG1 = IgG2 > IgG3 = IgG4 = IgA, but considered as whole, all isotypes were detected significantly more frequently in patients from the Awa area than in those from the Bsha area. The predominant expression of isotypes IgG1 and IgG2 suggests a preferential Th1 like immune response. Anti-Leishmania immunoserum stained only parasites and their debris, suggesting that most of the immunostaining was nonspecific.