Lymphoid/myeloid cell function

While changes in cell phenotypes have proved useful in some settings to characterize the immunotoxicity of xenobiotics,1 phenotypic analysis alone is often not a sensitive indicator of low dose immunotoxicity for many agents that alter immune function. Xenobiotics that exert selective toxicity on lymphoid and myeloid cells may be discovered through immunophenotypic analysis. However, most agents produce immunotoxicity at doses much lower than those required to produce cytotoxicity or interfere with primary lymphoid organ differentiation. Some of the most potent immunosuppressive chemicals that have been tested, such as cyclosporine A, do not alter immunophenotype at doses that are immunosuppressive. On the other hand, when phenotyping is linked to assessment of functional parameters of the cells, immunotoxic effects are more likely to be identified. 

There are literally hundreds of markers that are currently available for the mouse and human than can be used to characterize lymphoid and myeloid cells and subsets in primary and secondary lymphoid organs. Many of the markers expressed in mammals are highly conserved across species and have been designated as genetic clusters of differentiation (CD). CDs can be identified with fluorescently labeled monoclonal antibodies. As presented previously, when combined with other fluorescent probes, important information on intracellular biochemistry and cell function can be obtained. Many of the biochemical markers used by immunotoxicologists are common to other... 

The murine hematopoietic stem cell line Myl-D7 spontaneously differentiate along the lymphoid, myeloid and erythroid lineages. Myl-7 cells shows a strict stromal dependence for growth of self-renewing stem cells and express high levels of CSF-1 receptor (Itoh et al., 1996). We used this cell line to analyze the function of CSF-1 in maintaining multipotent cells. In an other attempt to characterize unknown factors that could sustain stem cells we... 

Lymphoid dendritic cells promote negative selection in the thymus. This may be attributed to their ability to induce fas-mediated apoptosis. Based on their ability to cause apoptosis and their ability to eliminate self-reactive T cells, lymphoid dendritic cells exhibit a regulatory function instead of a stimulatory immune effector function. Myeloid dendritic cells also have differential effects. For example, T cells can be primed to selectively activate THi responses by CD14-derived myeloid dendritic cells. Naive B cells can be activated in the presence of CD40L and IL-2 to secrete IgM by CD34+, CD14-derived myeloid dendritic cells. This effect on naive B cells is not observed with CD la-derived dendritic cells. 

SFlP-l is a tyrosine phosphatase found primarily in hematopoietic cells that is necessary for proper development of myeloid and lymphoid lineages. Its function is to dephosphorylate JAK2, thereby inactivating it. 

Colonna M, Navarro F, Bellon T, Llano M, Garcia P, Samaridis J, Angman L, Celia M, Lopez-Botet M (1997) A common inhibitory receptor for major histocompatibility complex class I molecules on human lymphoid and myelomonocytic cells. J Exp Med 186 1809-1818 Colonna M, Navarro F, Lopez-Botet M (1999) A novel family of inhibitory receptors for HLA class I molecules that modulate function of lymphoid and myeloid cells. Curr Top Microbiol Immunol 244 115-122... 

Colonna M, Nakajima H, Celia M (2000) A family of inhibitory and activating Ig-like receptors that modulate function of lymphoid and myeloid cells. Semin Immunol 12 121-127... 

CML arises from a defect in an early progenitor cell. Several cell lines may be affected, including myeloid, erythroid, megakaryocyte, and rarely, lymphoid lineages. These cells remain functional in chronic-phase CML, which is why patients in this phase are at low risk for developing infectious complications. 

The bone marrow functions as a primary lymphoid organ and serves as the principal source of uncommitted stem cells, including both myeloid and ery-throid precursor cells. The bone marrow architecture is highly organized and complex, consisting of a matrix or cellular stroma derived from local mesenchymal cells, as well as cells of hemopoietic parenchyma that are descendants... 

Hematopoiesis is the development of blood lineage cells from stem and progenitor cells, including both red blood cells (erythrocytes) and white blood cells (leukocytes). There are two types of hematopoietic tissue, myeloid and lymphoid tissue. Myeloid tissue is found in the bone marrow and produces red and white blood cells. Lymphoid tissue functions to mature lymphocytes and is found in the lymph nodes, thymus, spleen, and mucosa of respiratory and digestive tracts. 

The fiver is responsible for protein, carbohydrate and lipid metabolism, bile secretion and detoxification. With such critical metabolic functions it is often forgotten that it is also an important immune organ. In mammals the fiver is a mediator of systemic and local innate immunity and is an important site of immune regulation. Hepatic cells of the myeloid lineage are present, including Kupffer cells and DCs. Intrahepatic lymphocytes are also present but distinct in both phenotype and function from their counterparts in other organs and include both conventional T cells, B cells, NK cells and nonconventional lymphoid cells (natural killer T (NKT) cells, y5TCR+ T... 

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