Clement Beauchemin

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The fate of thymic emigrants had so far been studied using a variety of markers, each of which had inherent limitations as to stability, toxicity, or selectivity. We describe a new technique which relies on the in vivo injection of CFSE, an esterified vital dye hitherto used at 80 times lower concentrations for in vitro cell labeling. We show that CFSE(More)
Thymocytes not only receive signals from thymic epithelial cells but can also activate the latter, at least in the medulla. We have previously reported tyrosine phosphorylation of medullary epithelial cell substrates, after co-culture with thymocytes, and identified a number of protein tyrosine kinases in a line of thymic epithelial cells. We report here(More)
Skin tumors show variable infiltration by subtypes of inflammatory cells. The composition of these cellular infiltrates, particularly tumor-associated macrophages and dendritic cell numbers, may be responsible for skin tumor progression or regression. In addition, these cells may give rise to diagnostic dilemmas on immunohistochemical studies. The authors(More)
X irradiation of C57BL/Ka mice induces thymic lymphoma after a period of 8 to 36 weeks. This latency period represents an ideal time window in which to follow the development of prelymphoma cells that give rise to overt thymic lymphoma. Several attempts have been made to identify an unequivocal prelymphoma cell marker but these efforts have so far been(More)
Thymic lymphomas develop in C57BL/Ka mice within 36 weeks after split-dose X-irradiation. Lymphoma development can be abrogated in such mice by the injection of syngeneic bone marrow from healthy donors. The abrogation mechanism is unknown, but since bone marrow supplies the thymus with precursors of thymocytes and of dendritic cells, we tested the ability(More)
Thymic stromal cells were cultured in conditions which select for epithelial cells. These were then transformed in vitro by contact with N-methyl-N′-nitro-N-nitrosoguanidine and cloned at limit dilution. One of the clones was characterized as being of medullary origin on the basis of its reactivity with a battery of antibodies previously shown to(More)
Thymic medullary epithelial cells of the E-5 line were shown to form in vitro complexes with thymocytes resulting in no apparent modification to the thymocytes participating in the complex, but in tyrosine phosphorylation on a glycoprotein associated with the epithelial adhesion molecule. Because signal transduction from lymphocytes to stromal cells is(More)
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