8536d_ch02_024-0568/5/02 4: 02 PM Page 26 mac79 Mac 79: 45_BW: Godsby et al. /Immunology 5e apacity for self-renewal and are committed to a particular cell possible to identify many hematopoietic growth factors. In neage. Common lymphoid progenitor cells give rise to B, T, these in vitro systems, bone-marrow stromal cells are cul- and nk(natural killer)cells and some dendritic cells. Myeloid tured to form a layer of cells that adhere to a petri dish stem cells generate progenitors of red blood cells(erythro- freshly isolated bone-marrow hematopoietic cells placed on ytes), many of the various white blood cells(neutrophils, this layer will grow, divide, and produce large visible colonies eosinophils, basophils, monocytes, mast cells, dendritic cells),(Figure 2-2). If the cells have been cultured in semisolid agar, nd platelets Progenitor commitment depends on the acquisi- their progeny will be immobilized and can be analyzed for tion of responsiveness to particular growth factors and cy- cell types. Colonies that contain stem cells can be replated to tokines. When the appropriate factors and cytokines are produce mixed colonies that contain different cell types, in present, progenitor cells proliferate and differentiate into the cluding progenitor cells of different cell lineages. In contrast, corresponding cell type, either a mature erythrocyte, a partic- progenitor cells, while capable of division, cannot be replated ular type of leukocyte, or a platelet-generating cell(the and produce lineage-restricted colonies. megakaryocyte). Red and white blood cells pass into bone Various growth factors are required for the survival, pro- marrow channels, from which they enter the circulation liferation, differentiation, and maturation of hematopoietic In bone marrow, hematopoietic cells grow and mature on cells in culture. These growth factors, the hematopoietic a meshwork of stromal cells, which are nonhematopoietic cytokines, are identified by their ability to stimulate the for- cells that support the growth and differentiation of hema- mation of hematopoietic cell colonies in bone-marrow topoietic cells Stromal cells include fat cells, endothelial cells, cultures. Among the cytokines detected in this way was a ibroblasts, and macrophages Stromal cells influence the dif- family of acidic glycoproteins, the colony-stimulating fac- ferentiation of hematopoietic stem cells by providing a tors(CSFs), named for their ability to induce the formation hematopoietic-inducing microenvironment(HIM)con- of distinct hematopoietic cell lines. Another importan sisting of a cellular matrix and factors that promote growth hematopoietic cytokine detected by this method was the gly- and differentiation. Many of these hematopoietic growth coprotein erythropoietin(EPO). Produced by the kidney, factors are soluble agents that arrive at their target cells by this cytokine induces the terminal development of erythro diffusion, others are membrane-bound molecules on the cytes and regulates the production of red blood cells. Fur surface of stromal cells that require cell-to-cell contact be- ther studies showed that the ability of a given cytokine to tween the responding cells and the stromal cells. During in- signal growth and differentiation is dependent upon the fection, hematopoiesis is stimulated by the production of presence of a receptor for that cytokine on the surface of the hematopoietic growth factors by activated macrophages and target cell--commitment of a progenitor cell to a particular Tcells differentiation pathway is associated with the expression of membrane receptors that are specific for particular cy Hematopoiesis Can Be Studied In Vitro tokines. Many cytokines and their receptors have since been shown to play essential roles in hematopoiesis. This topic is Cell-culture systems that can support the growth and differ- explored much more fully in the chapter on cytokines entiation of lymphoid and myeloid stem cells have made it Chapter 11) Adherent layer of marrow cells Culture in semioli Visible colonies of bone-marrow cells ∠s8、g 發 FIGURE2-2(a) Experimental scheme for culturing hematopoietic in long-term culture of human bone marrow.[Photograph from ells Adherent bone-marrow stromal cells form a matrix on which M.J. Cline and D. W. Golde, 1979, Nature 277: 180; reprinted by the hematopoietic cells proliferate. Single cells can be transferred permission;@ 1979 Macmillan Magazines Ltd, micrograph cour. to semisolid agar for colony growth and the colonies analyzed for tesy of S. quan J differentiated cell types. (b) Scanning electron micrograph of cells26 PART I Introduction capacity for self-renewal and are committed to a particular cell lineage. Common lymphoid progenitor cells give rise to B, T, and NK (natural killer) cells and some dendritic cells. Myeloid stem cells generate progenitors of red blood cells (erythro￾cytes), many of the various white blood cells (neutrophils, eosinophils, basophils, monocytes, mast cells, dendritic cells), and platelets. Progenitor commitment depends on the acquisi￾tion of responsiveness to particular growth factors and cy￾tokines. When the appropriate factors and cytokines are present, progenitor cells proliferate and differentiate into the corresponding cell type, either a mature erythrocyte, a partic￾ular type of leukocyte, or a platelet-generating cell (the megakaryocyte). Red and white blood cells pass into bone￾marrow channels, from which they enter the circulation. In bone marrow, hematopoietic cells grow and mature on a meshwork of stromal cells, which are nonhematopoietic cells that support the growth and differentiation of hema￾topoietic cells. Stromal cells include fat cells, endothelial cells, fibroblasts, and macrophages. Stromal cells influence the dif￾ferentiation of hematopoietic stem cells by providing a hematopoietic-inducing microenvironment (HIM) con￾sisting of a cellular matrix and factors that promote growth and differentiation. Many of these hematopoietic growth factors are soluble agents that arrive at their target cells by diffusion, others are membrane-bound molecules on the surface of stromal cells that require cell-to-cell contact be￾tween the responding cells and the stromal cells. During in￾fection, hematopoiesis is stimulated by the production of hematopoietic growth factors by activated macrophages and T cells. Hematopoiesis Can Be Studied In Vitro Cell-culture systems that can support the growth and differ￾entiation of lymphoid and myeloid stem cells have made it possible to identify many hematopoietic growth factors. In these in vitro systems, bone-marrow stromal cells are cul￾tured to form a layer of cells that adhere to a petri dish; freshly isolated bone-marrow hematopoietic cells placed on this layer will grow, divide, and produce large visible colonies (Figure 2-2). If the cells have been cultured in semisolid agar, their progeny will be immobilized and can be analyzed for cell types. Colonies that contain stem cells can be replated to produce mixed colonies that contain different cell types, in￾cluding progenitor cells of different cell lineages. In contrast, progenitor cells, while capable of division, cannot be replated and produce lineage-restricted colonies. Various growth factors are required for the survival, pro￾liferation, differentiation, and maturation of hematopoietic cells in culture. These growth factors, the hematopoietic cytokines, are identified by their ability to stimulate the for￾mation of hematopoietic cell colonies in bone-marrow cultures. Among the cytokines detected in this way was a family of acidic glycoproteins, the colony-stimulating fac￾tors (CSFs), named for their ability to induce the formation of distinct hematopoietic cell lines. Another important hematopoietic cytokine detected by this method was the gly￾coprotein erythropoietin (EPO). Produced by the kidney, this cytokine induces the terminal development of erythro￾cytes and regulates the production of red blood cells. Fur￾ther studies showed that the ability of a given cytokine to signal growth and differentiation is dependent upon the presence of a receptor for that cytokine on the surface of the target cell—commitment of a progenitor cell to a particular differentiation pathway is associated with the expression of membrane receptors that are specific for particular cy￾tokines. Many cytokines and their receptors have since been shown to play essential roles in hematopoiesis. This topic is explored much more fully in the chapter on cytokines (Chapter 11). FIGURE 2-2 (a) Experimental scheme for culturing hematopoietic cells. Adherent bone-marrow stromal cells form a matrix on which the hematopoietic cells proliferate. Single cells can be transferred to semisolid agar for colony growth and the colonies analyzed for differentiated cell types. (b) Scanning electron micrograph of cells Add fresh bone￾marrow cells Culture in semisolid agar Adherent layer of stromal cells Visible colonies of bone-marrow cells (a) (b) in long-term culture of human bone marrow. [Photograph from M. J. Cline and D. W. Golde, 1979, Nature 277:180; reprinted by permission; © 1979 Macmillan Magazines Ltd., micrograph cour￾tesy of S. Quan.] 8536d_ch02_024-056 8/5/02 4:02 PM Page 26 mac79 Mac 79:45_BW:Goldsby et al. / Immunology 5e: