Mechanism of T cell proliferation in vivo: analysis of IL-2 receptor expression and activation of c-myc and c-myb oncogenes during lymphatic regeneration.
The mechanism of T cell proliferation was studied using in vivo lymphatic regeneration as the model. Lymphatic regeneration was induced by injecting a sublethal dose (300 mg/kg) of cyclophosphamide (Cy) into mice. Majority of the regenerating splenic T cells were found to be in the cell cycle, nearly 30% being found in S/G2+M phases resembling the ratio obtained for mitogen activated T cells in vitro. Expression of interleukin-2 receptor (IL-2R) was defined by the monoclonal anti-IL-2R antibody, AMT-13. Only 1-3% of regenerating T cells were IL-2R positive (while about 30% of the in vitro activated T cells were IL-2R positive). Accordingly, these cells did not respond to IL-2 in vitro. However, when the freshly isolated regenerating T cells were cultured in the presence of Con A or PMA + ionophore A 23187, IL-2R was readily induced. The regenerating T cells were further analyzed for the expression of the cellular oncogenes c-myc and c-myb. These cells expressed about three times more c-myb mRNA than Con A-stimulated T cells and the levels were comparable to those seen in thymocytes. By contrast, the amount of c-myc mRNA was similar in the regenerating T cells and in Con A-activated T cells, but weak or barely detectable in splenocytes and thymocytes. Taken together, our results imply that the vigorous T cell proliferation during cyclophosphamide-induced lymphatic regeneration is independent of the IL-2/IL-2R hormone system, like T-cell precursor proliferation in the thymus, and is characterized by both high c-myb expression typical for thymocytes and high c-myc expression typical for in vitro proliferation-activated T cells.
Sihvola
M
M
Department of Bacteriology, University of Helsinki, Finland.
Sistonen
L
L
Alitalo
K
K
Hurme
M
M
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002455:Cell Division; D003208:Concanavalin A / Q000494:pharmacology; D003520:Cyclophosphamide / Q000494:pharmacology; D005786:Gene Expression Regulation; D008208:Lymphatic System / Q000502:physiology*; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D020598:Proto-Oncogene Proteins c-myb; D016271:Proto-Oncogene Proteins c-myc; D011519:Proto-Oncogenes; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis* / Q000235:genetics; D012038:Regeneration / Q000187:drug effects; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D011518:Proto-Oncogene Proteins; D020598:Proto-Oncogene Proteins c-myb; D016271:Proto-Oncogene Proteins c-myc; D015375:Receptors, Interleukin-2; D003208:Concanavalin A; D000001:Calcimycin; D003520:Cyclophosphamide; D013755:Tetradecanoylphorbol Acetate