Immunological mechanisms play an important role in the pathogenesis of psoriasis. Lesional psoriatic skin-derived T-cell clones have been shown to stimulate keratinocyte proliferation and to predominantly express a T-helper type 1 cytokine pattern. However, T-helper type 2-like cytokines have also been identified in some psoriatic T-cell clones. In parallel to the T-helper type 1/type 2 dichotomy, a distinction between interferon-gamma-induced (classically activated) macrophages and interleukin-4/glucocorticoid-induced (alternatively activated) macrophages has been put forward as a conceptual framework for a better understanding of immunopathological processes. In the present study, the phenotype of mononuclear phagocytes in psoriatic skin lesions (n = 21), allergic contact dermatitis (n = 4) and normal skin (n = 2) was investigated using a panel of monoclonal antibodies (mAb) against monocytes/macrophages and dendritic cells (mAb MS-1, RM 3/1, and 25F9 against subsets of in vitro alternatively activated macrophages, and mAb against myeloid antigens CD1a, CD11b, CD11c, CD34, CD36, and CD68). With regard to mononuclear phagocytes, psoriatic skin was found to be compartmentalized into epidermis, subepidermal space, and upper and lower dermis. RM 3/1++ +, MS-1+/-, 25F9- dendritic macrophages previously classified as type II alternatively activated macrophages were the dominant dermal macrophage population in psoriatic skin, while intraepidermal and epithelium-lining macrophages expressed a different, presumably classically activated, macrophage phenotype (RM 3/1-, MS-1-, 25F9-, CD68+2, CD11b+2). In allergic contact dermatitis, a classical T-helper type 1 disease, RM 3/1++ + macrophages were less prominent. Since MS-1 high molecular weight protein is much more sensitive to interferon-gamma-induced suppression than RM 3/1 antigen, a predominance of T-helper type 1 cytokines in psoriasis could explain why dermal dendritic macrophages do not express the fully induced MS-1++ +, RM 3/1++ +, 25F9+/- phenotype of type I alternatively activated macrophages.

Immunological mechanisms play an important role in the pathogenesis of psoriasis. Lesional psoriatic skin-derived T-cell clones have been shown to stimulate keratinocyte proliferation and to predominantly express a T-helper type 1 cytokine pattern. However, T-helper type 2-like cytokines have also been identified in some psoriatic T-cell clones. In parallel to the T-helper type 1/type 2 dichotomy, a distinction between interferon-gamma-induced (classically activated) macrophages and interleukin-4/glucocorticoid-induced (alternatively activated) macrophages has been put forward as a conceptual framework for a better understanding of immunopathological processes. In the present study, the phenotype of mononuclear phagocytes in psoriatic skin lesions (n = 21), allergic contact dermatitis (n = 4) and normal skin (n = 2) was investigated using a panel of monoclonal antibodies (mAb) against monocytes/macrophages and dendritic cells (mAb MS-1, RM 3/1, and 25F9 against subsets of in vitro alternatively activated macrophages, and mAb against myeloid antigens CD1a, CD11b, CD11c, CD34, CD36, and CD68). With regard to mononuclear phagocytes, psoriatic skin was found to be compartmentalized into epidermis, subepidermal space, and upper and lower dermis. RM 3/1++ +, MS-1+/-, 25F9- dendritic macrophages previously classified as type II alternatively activated macrophages were the dominant dermal macrophage population in psoriatic skin, while intraepidermal and epithelium-lining macrophages expressed a different, presumably classically activated, macrophage phenotype (RM 3/1-, MS-1-, 25F9-, CD68+2, CD11b+2). In allergic contact dermatitis, a classical T-helper type 1 disease, RM 3/1++ + macrophages were less prominent. Since MS-1 high molecular weight protein is much more sensitive to interferon-gamma-induced suppression than RM 3/1 antigen, a predominance of T-helper type 1 cytokines in psoriasis could explain why dermal dendritic macrophages do not express the fully induced MS-1++ +, RM 3/1++ +, 25F9+/- phenotype of type I alternatively activated macrophages.

Between 1982 and 1995, over 700 HIV-infected patients with different skin diseases were registered at the Department of Dermatology, Benjamin Franklin Medical Center, The Free University of Berlin. Thirty-six of them (approximately 5%) were diagnosed as having psoriasis. This is clearly a higher prevalence of psoriasis than in the general population (1-2%). If psoriasis lesions are not clinically seen before diagnosis of HIV infection, the disease will preferentially (approximately 80% of these cases) appear during the late stages of the infection (CD4/CD8 ratio < 0.4). Six of the 36 patients with HIV-related psoriasis (= 16%) were found to have severe disease, showing an exsudative clinical picture. In this paper we report in detail on two representative cases from this group of patients. Histological examination also revealed exsudative changes in HIV-infected patients with clinically moderate psoriasis. Immunohistochemically, HIV-related psoriasis showed a moderately decreased number of infiltrating T-cells, in contrast to psoriatic skin from non-infected patients. A marked difference was the reduced expression of the lymphocyte antigen OPD-4 in HIV-related psoriasis. Routine antipsoriatic treatment modalities in combination with systemic retinoids and phototherapy (SUP/PUVA) were successful in the treatment of severe exsudative psoriasis in HIV patients, but the course of the disease was prolonged and exacerbation was more frequent. HIV-related psoriasis was found not to influence the underlying HIV infection.