J Histochem Cytochem 1997 Dec;45(12):1665-72 

Constant detection of CD2, CD3, CD4, and CD5 in fixed and paraffin-embedded tissue using the peroxidase-mediated deposition of biotin-tyramide. 

Malisius R, Merz H, Heinz B, Gafumbegete E, Koch BU, Feller AC. 

Department of Pathology, Medical University of Lubeck, Lubeck, Germany.             

    Immunohistochemical methods are widely used for diagnostic purposes in histopathology. However, the use of most monoclonal anti-leukocyte antibodies is limited to frozen tissues. Initially, it was believed that formalin fixation in particular, which is the gold standard for morphological tissue preservation, destroys most of the antigen binding sites. In recent years, protease digestion and the introduction of microwave techniques have significantly enhanced the sensitivity of immunohistochemical techniques, and a variety of hidden antigen sites in formalin-fixed tissue have been retrieved for initially unreactive antibodies. It therefore became clear that many of the leukocyte antigens are not irreversibly destroyed but are most probably masked during the fixation process. We developed a technique combining optimized pretreatment of formalin-fixed tissue with a dramatic enhancement of the immunohistochemical sensitivity and named it the ImmunoMax method. The ImmunoMax method proves that by optimizing the technique at the following three levels it is possible to detect formalin-sensitive leukocyte antigens: (a) standard fixation of the tissue; (b) sufficient antigen unmasking; and (c) increasing the substrate turnover by multiplication of binding sites with subsequent enhancement of the immunohistochemical reaction. Using this optimized ImmunoMax method, we were able to detect CD2, CD3, CD4, and CD5 with conventional monoclonal antibodies in formalin-fixed, paraffin-embedded tissue specimens of various lymphoid tissues.

Nat Med 1999 Mar;5(3):344-6 

CCR5- and CXCR4-tropic HIV-1 are equally cytopathic for their T-cell targets in human lymphoid tissue. 

Grivel JC, Margolis LB. 

Laboratory of Molecular and Cellular Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA. 

    A rapid decline in T-cell counts and the progression to AIDS is often associated with a switch from CCR5-tropic (R5) HIV-1 to CXCR4-tropic (X4) HIV-1 or R5/X4 HIV-1 variants. Experimental infection with R5 HIV-1 causes less T-cell depletion than infection with X4 or R5/X4 variants in T-cell cultures, in ex vivo infected human lymphoid tissue and in SCID/hu mice, despite similar replication levels. Experimental genetic changes in those sequences in gp120 that transform R5 HIV-1 variants into otherwise isogenic X4 viruses make them highly cytopathic. Thus, it is now believed that R5 variants are less cytopathic for T cells than are X4 variants. However, it is not known why CCR5-mediated HIV-1 infection does not lead to a massive CD4+ T-cell depletion, as occurs in CXCR4-mediated HIV-1 infection. Here we demonstrate that R5 HIV-1 isolates are indeed highly cytopathic, but only for CCR5+/CD4+ T cells. Because these cells constitute only a small fraction of CD4+ T cells, their depletion does not substantially change the total CD4+ T-cell count. These results may explain why the clinical stage of HIV disease correlates with viral tropism.

J Virol 2001 Jul;75(14):6710-3 

Plasmacytoid dendritic cells are highly susceptible to human immunodeficiency virus type 1 infection and release infectious virus. 

Patterson S, Rae A, Hockey N, Gilmour J, Gotch F. 

Department of Immunology, Imperial College School of Medicine,  United Kingdom. 

    Plasmacytoid dendritic cells (pcDC) and myeloid dendritic cells (myDC) are shown to express CD4 and low levels of CCR5 and CXCR4, but only myDC express DC SIGN, a C-type lectin that binds human immunodeficiency virus but does not mediate virus entry. Both DC types were more susceptible to infection with a macrophage than a lymphotropic strain of human immunodeficiency virus type 1, but pcDC were more readily infected than myDC.

Nat Immunol 2000 Oct;1(4):305-10 

 Plasmacytoid dendritic cells activated by influenza virus and CD40L drive a potent TH1 polarization. 

Cella M, Facchetti F, Lanzavecchia A, Colonna M. 

Basel Institute for Immunology, CH-4005 Basel, Switzerland. 

    Plasmacytoid dendritic cells (PDCs) are a subset of dendritic cells present in human blood and inflamed lymph nodes. Here we show that blood PDCs, when stimulated with influenza virus and CD40L in vitro, undergo a maturation process characterized by up-regulation of major histocompatibility complex proteins and adhesion and costimulatory molecules. In addition, PDCs down-regulate CXCR3 and L-selectin, which mediate migration and homing of these cells into the lymph node. Mature PDCs efficiently stimulate T cells and drive a potent TH1 polarization in vitro, which is mediated by the synergistic effect of interleukin 12 and type 1 interferon. In vivo, mature PDCs are found in secondary lymphoid organs, where they represent the principal source of type 1 interferon during inflammation. Thus, PDCs probably participate in antiviral and pro-inflammatory responses, rather than in TH2 polarization and tolerance induction.

Am J Pathol 1988 Oct;133(1):15-21 

Plasmacytoid T cells. Immunohistochemical evidence for their monocyte/macrophage origin. 

Facchetti F, de Wolf-Peeters C, Mason DY, Pulford K, van den Oord JJ, Desmet VJ. Department of Pathology, Catholic University of Leuven, Belgium. 

    To elucidate the lineage of plasmacytoid T cells, their immunophenotype was studied in reactive lymph nodes with a broad panel of monoclonal antibodies. Plasmacytoid T cells expressed several myelomonocytic markers, and almost all markers highly selective for macrophages. They lacked granulocyte-associated and B or T lymphocyte-associated antigens. These results provide strong evidence that plasmacytoid T cells are of monocyte lineage.

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Settembre 2002