Dendritic cells and macrophages can mature independently from a human bone marrow-derived, post-colony-forming unit intermediate.

CD34+ precursors in normal human bone marrow (BM) generate large numbers of dendritic cells alongside macrophages and granulocytic precursors when cultured for 12 to 14 days in c-kit ligand, granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor-alpha (TNF-alpha). This study reports an intermediate cell type that develops by day 6, and has the potential to differentiate into either macrophages or dendritic cells. When the d6 progeny are depleted of mature macrophages and residual CD34+ precursors, a discrete CD14+ HLA-DR+ population persists in addition to immunostimulatory CD14- HLA-DR() dendritic cells.

Low levels of HIV-1 infection in cutaneous dendritic cells promote extensive viral replication upon binding to memory CD4+ T cells.

Earlier work has identified a cell population that replicates HIV-1 in the absence of standard T cell stimuli. The system consists of dendritic cells and memory T lymphocytes that emigrate from organ cultures of human skin and together support a productive infection with HIV-1. These emigrants resemble cells that can be found in mucous membranes and that normally traffic in afferent lymph.

Susceptibility of dendritic cells to HIV-1 infection in vitro.

We review recent work on the extent of HIV-1 infection of dendritic cells (DCs) and the consequences of exposure to virus. The reported levels of infection of DCs from blood have varied from "explosive" to "undetectable." The only study that used sorted DCs demonstrated little if any infectability, which may not be surprising given the very low levels of CD4 on the populations that were studied.

Conjugates of dendritic cells and memory T lymphocytes from skin facilitate productive infection with HIV-1.

Experimentally, a productive infection with HIV-1 requires that virus be administered to T cells that are activated by mitogens. We describe a productive milieu for HIV-1 within the confines of normal skin that does not require standard stimuli. The milieu consists of dendritic cells and T cells that emigrate from skin and produce distinctive stable, nonproliferating conjugates.

Human blood contains two subsets of dendritic cells, one immunologically mature and the other immature.

Two subsets of dendritic cells, differing in T-cell stimulatory function, have been purified directly from human blood. Both subsets are positive for major histocompatibility complex (MHC) class II expression and negative for lineage-specific antigens (e.g.

Infection and apoptotic cell death of CD4+ T cells during an immune response to HIV-1-pulsed dendritic cells.

Interacting dendritic cells and helper CD4+ lymphocytes form a microenvironment that is permissive for HIV-1 replication. The virus need only be pulsed initially onto the dendritic cells, which then transfer HIV-1 to the lymphocytes that are responding to presented antigens or superantigens. We have pursued underlying mechanisms in this system, because it provides a model for the infection of antigen-reactive, primary T cells.

Dendritic cells freshly isolated from human blood express CD4 and mature into typical immunostimulatory dendritic cells after culture in monocyte-conditioned medium.

A procedure has been developed to isolate dendritic cells to a high degree of purity from fresh blood. Prior enrichment methods have relied upon an initial 1-2-d culture period. Purified fresh isolates lack the characteristic morphology, phenotype, and immunostimulatory function of dendritic cells.

Dendritic cells exposed to human immunodeficiency virus type-1 transmit a vigorous cytopathic infection to CD4+ T cells.

The paucity of virus-laden CD4+ cells in individuals infected with human immunodeficiency virus type-1 (HIV-1) contrasts with the greatly reduced numbers and function of these lymphocytes. A pathway is described whereby dendritic cells carry HIV-1 to uninfected T cells, amplifying the cytopathic effects of small amounts of virus. After exposure to HIV-1, dendritic cells continue to present superantigens and antigens, forming clusters with T cells that are driven to replicate.

Use of the fluorescence activated cell sorter to enrich dendritic cells from mouse spleen.

Dendritic cells are a specialized but trace population of antigen presenting cells that always have been enriched by multi-step procedures over a period of 1 or more days in tissue culture. Here we describe the isolation of dendritic cells from fresh mouse spleen suspensions using the FACS and a monoclonal antibody, N418, to the p150/90 member of the leukocyte integrin family (Metlay et al., 1990).