21 research outputs found
Microenvironments of T and B lymphocytes : a light- and electromicroscopic study
Peripheral blood cells- erythrocytes, granulocytes, monocytes, thrombocytes
and lymphocytes-are the end products of a differentiation process which
occurs in the bone marrow and, in rodents, also in the spleen. Normal
haemopoietic tissue is a cell renewal system with an accurate balance between
cell production originating from pluripotent haemopoietic stem cells and
continuous cell loss. The important function of haemopoietic stem cells was
emphasized by Till and McCulloch (1961) in bone marrow transplantation
studies in mice. They noted that intravenous injection of small numbers of
bone marrow cells into lethally irradiated syngeneic recipient mice caused the
appearance of haemopoietic colonies in the spleen of the recipient mice. These
colonies consisted either of erythroid, gran uloid, megakaryocytic or mixed cell
populations (Curry and Trentln, 1967). The technique used by Till and
McCulloch is known as the "spleen colony assay" and has established two
major qualities of haemopoietic stem cells: (I) they have the capacity of self
replication (Trentin and Fahlberg, 1963; Curry et a!., 1967) and (2) they are
pluripotent since they give rise to clones of different cell types of which the
differentiated "end" cells recirculate in the blood (Till and McCulloch, 1961;
Becker eta!., 1963; Till, 1976). In contrast to erythroid and myeloid colonies,
lymphoid colonies were not detectable with the spleen colony assay; however,
Ford et al. (1966), Micklem et a!. (1966), and Wu et a!. (1968) demonstrated
with chromosome marker techniques that lymphoid cells were also derived
from pluripotent haemopoietic stem cells.
One of the major questions in cell biological investigations of haemopoiesis
concerns the factors which determine the commitment and differentiation of
pluripotent haemopoietic stem cells. At present it is generally accepted that
two types of factors are involved in the regulation of haemopoiesis: (I)
microenvironmental factors (see 1.2), and (2) humoral factors (see 1.4)
Crosstalk in the mouse thymus
The development of mature T cells within the thymus is dependent upon intact cortical and medullary microenvironments. In turn, thymic microenvironment themselves are dependent on lymphoid cells to maintain their integrity. Here, Willem van Ewijk and colleagues discuss experiments that have established the phenomenon of ‘crosstalk’ within the mouse thymus and suggest a mechanism whereby lymphoid and stromal cells influence each other in a consecutive manner during T-cell development
Inhibition of proliferation and differentiation during early T cell development by anti-transferrin receptor antibody
Proliferating cells require iron and, therefore, express the transferrin receptor (CD71) that mediates cellular iron uptake. Cycling thymocytes, which have the CD4−8−3−, CD4−8+3−, or CD4+8+3− phenotypes, also express CD71. The importance of CD71-mediated iron uptake for proliferation and maturation of thymocytes was studied using fetal thymus organ cultures at day 14 of gestation and treating them for 7 days with a CD71 monoclonal antibody (mAb). The intracellular iron deficiency caused by this treatment, inhibits both proliferation and maturation of the thymocytes. Cell recovery was reduced by 60%, but cells still expanded tenfold during the culture. Remarkably, the final maturation of αβ T cells was completely blocked as no thymocytes with low or high CD3/αβTcR expression developed. Moreover, only few cells reached the CD4+8+3− stage of T cell development. CD4−8−3− thymocytes, however, as well as its CD44−25+ subset developed in normal numbers, suggesting that CD44−25+ CD4−8−3− cells, or their immediate progeny, were most vulnerable to CD71 mAb treatment. The development of γδ T cells, which also express CD71, was not affected in these cultures. This suggests that γδ T cells are either less iron-dependent or possess alternative iron-uptake mechanisms. Thus, our observation
Stepwise development of thymic microenvironments in vivo is regulated by thymocyte subsets
T-cell development is under the tight control of thymic microenvironments.
Conversely, the integrity of thymic microenvironments depends on the
physical presence of developing thymocytes, a phenomenon designated as
'thymic crosstalk'. We now show, using three types of immunodeficient
mice, i.e. CD3(epsilon) transgenic mice, RAG(null) mice and
RAG(null)-bone-marrow-transplanted CD3(epsilon) transgenic mice, that the
control point in lymphoid development where triple negative
(CD3(-),CD4(-),CD8(-)) thymocytes progress from CD44(+)CD25(-) towards
CD44(-)CD25(+), influences the development of epithelial cells, critically
inducing the extra, third dimension in the organization of the epithelial
cells in the cortex. This tertiary configuration of the thymic epithelium
is a typical feature for the thymus, enabling lymphostromal interaction
during T-cell development. Crosstalk signals at this control point also
induce the formation of thymic nurse cells. Moreover, our data indicate
that establishment of a thymic cortex is a prerequisite for the
development of the thymic medulla. Thus, differentiating thymocytes
regulate the morphogenesis of thymic microenvironments in a stepwise
fashion
The monoclonal antibody ER-BMDM1 recognizes a macrophage and dendritic cell differentiation antigen with aminopeptidase activity
Abstract
Here we describe the reactivity of monoclonal antibody (mAb) ER-BMDM1, directed against a 160-kDa cell membrane-associated antigen (Ag) with aminopeptidase activity. The aminopeptidase recognized by ER-BMDM1 is present on various mouse macrophage (MΦ) and dendritic cell (DC) subpopulations as well as on microvillous epithelia. Analysis of ER-BMDM1 Ag expression in in vitro models of MΦ maturation revealed that the Ag is expressed at increasing levels upon maturation of MΦ. In vivo, high level expression of the ER-BMDM1 Ag occurs after thmonocytic stage of maturation, since bone marrow cells and peripheral blood monocytes are essentially ER-BMDM1 negative. Analysis of isolated-resident and elicited MΦ populations showed that ER-BMDM1 recognizes a specific subpopulation of mature MΦ: only some resident peritoneal and alveolar MΦ are ER-BMDM1 positive, whereas virtually all thioglycollate-elicited peritoneal exudate MΦ bind the mAb. In lymphoid organs, a subpopulation of MΦ is recognized as well as interdigitating cells (IDC) located in T cell areas. Phenotypic analysis of isolated DC- the in vitro equivalents of IDC - from spleen and lymph nodes confirmed that the majority of this important antigen-presenting cell population expresses the ER-BMDM1 aminopeptidase. The molecular characteristics of the ER-BMDM1 Ag suggest that it may represent the mouse homolog of human CD13
Differential inhibition of macrophage proliferation by anti-transferrin receptor antibody ER-MP21: correlation to macrophage differentiation stage
Abstract
Monoclonal antibodies (mAbs) directed against the transferrin receptor are known to inhibit proliferation of cells due to iron deprivation. Some cell types, however, escape from growth inhibition by a mechanism which is unclear at present. This mechanism is the subject of the present study. We investigated the differential growth inhibition caused by anti-transferrin receptor mAb ER-MP21 in connection with the differentiation of murine macrophages (Mφ). Therefore, we applied two models of Mφ differentiation, namely, culture of bone marrow cells in the presence of M-CSF and a panel of Mφ cell lines ordered in a linear differentiation sequence. In both models we observed that proliferation of Mφ precursors was strongly inhibited by ER-MP21. In contrast, proliferation of more mature stages of Mφ differentiation was hardly affected. Remarkably, iron uptake by Mφ precursor and mature Mφ cell lines was inhibited by ER-MP21 to the same extent. However, mature Mφ cell lines showed an iron uptake two-to threefold higher than that of Mφ precursor cell lines. These observations strongly suggest that mature Mφ escape from ER-MP21-mediated growth inhibition, because these cells take up more iron than is actually needed for proliferation. Furthermore, we found that enhanced iron uptake by mature Mφ is not necessarily accompanied by a higher cell surface expression of transferrin receptors, thus suggesting an increased recycling of transferrin receptors in mature Mφ
Markers of mouse macrophage development detected by monoclonal antibodies
In this review, we present and discuss a selected panel of antibody-defined markers expressed during different stages of mouse macrophage d
Heterogeneity of mouse spleen dendritic cells: in vivo phagocytic activity, expression of macrophage markers, and subpopulation turnover
In the normal mouse spleen, two distinct populations of dendritic cells
(DC) are present that differ in microanatomical location. The major
population of marginal DC is found in the "marginal zone bridging
channels" and extends into the red pulp. The interdigitating cells (IDC)
are localized in the T cell areas in the white pulp. The aim of the
present study was to characterize these two splenic DC populations with
regard to their phenotype, in vivo phagocytic function, and turnover. Both
marginal DC and IDC are CD11c+ and CD13+, but only IDC are NLDC-145+ and
CD8alpha+. Notably, both populations, when freshly isolated, express the
macrophage markers F4/80, BM8, and Mac-1. To study the phagocytic capacity
of these cells, we employed the macrophage "suicide" technique by
injecting liposomes loaded with clodronate i.v. Marginal DC, but not IDC,
were eliminated by this treatment. Phagocytosis of DiI-labeled liposomes
by DC confirmed this finding. The two DC populations differed
significantly with regard to their turnover rates, as studied in a
transgenic mouse model of conditional depletion of DC populations with
high turnover. In these mice, marginal DC were completely eliminated, but
the IDC population remained virtually intact. From these data we conclude
that the marginal DC population has a high turnover, in contrast to the
IDC population. Taken together, the present results indicate that marginal
DC and IDC represent two essentially distinct populations of DC in the
mouse spleen. They differ not only in location, but also in phenotype,
phagocytic ability, and turnover
Mice lacking the MHC class II transactivator (CIITA) show tissue-specific impairment of MHC class II expression
CIITA activates the expression of multiple genes involved in antigen presentation and it is believed to be required for both constitutive and IFN\xce\xb3-inducible expression of these genes. To understand the role of CIITA in vivo, we have used gene targeting to generate mice that lack CIITA. CIITA-deficient (-/-) mice do not express conventional MHC class II molecules on the surface of splenic B cells and dendritic cells. In addition, macrophages resident in the peritoneal cavity do not express MHC class II molecules upon IFN\xce\xb3 stimulation nor do somatic tissues of mice injected with IFN\xce\xb3, in contrast with wild-type mice. The levels of li and H-2M gene transcripts are substantially decreased but not absent in CIITA (-/-) mice. The transcription of nonconventional MHC class II genes is, however, not affected by CIITA deficiency. A subset of thymic epithelial cells express MHC class II molecules. Nonetheless, very few mature CD4 T cells are present in the periphery of CIITA (-/-) mice despite MHC class II expression in the thymus. Consequently, CIITA (-/-) mice are impaired in T-dependent antigen responses and MHC class II-mediated allogeneic reponses
Distinct mouse bone marrow macrophage precursors identified by differential expression of ER-MP12 and ER-MP20 antigens
The characterization of early branch points in the differentiation of leukocytes requires identification of precursor cells in the bone marrow. Recently, we produced two monoclonal antibodies, ER-MP12 and ER-MP20, which in two-color flow-cytometric analysis divide the murine bone marrow into six defined subsets. Here we show, using fluorescence-activated cell sorting followed by macrophage colony-stimulating factor-stimulated culture in soft agar, that precursors of the mononuclear phagocyte system reside only within the ER-MP12hi20−, ER-MP12+20+ and ER-MP12−20hi bone marrow subsets. Together, these subsets comprise 15% of nucleated bone marrow cells. Furthermore, we provide evidence that the macrophage precursors present in these subsets represent successive stages in a maturation sequence where the most immature ER-MP12hi20− cells develop via the ER-MP12+20+ stage into ER-MP12−20hi monocytes