Peripheral blood mononuclear cells (PBMC) collected from subjects prior to treatment and post-treatment with a vaccine composed of leishmania antigens were analyzed by flow cytometry. Upon analysis, it was noticed that lymphocyte subsets (LS) varied with psoriasis area and severity index (PASI) range (1-10, 11-20 and 21-72). Pre-treatment absolute values of gated LS were as follows. CD4+CD8-, CD3+CD8-, CD8+CD3+, CD8+CD4- and CD8+HLA- decreased in PBMC as PASI increased, suggesting migration from the blood to the skin. Contrary to the previous finding, the following LS, CD8+HLA+ and HLA+CD8-, and membrane surface immunoglobulin IgA+, IgD+ and IgM+ increased in PBMC as PASI increased, suggesting activation and proliferation by unknown antigens. After treatment with seven doses of AS100, the following LS, CD3+CD8-, CD8+CD3-, HLA+CD8-, CD8+HLA+ and CD4+CD8-, increased, while CD8+CD3+, CD8+HLA-, CD19 and CD8+CD4+ decreased in PBMC.