Granulocyte-macrophage colony-stimulating factor augmentation of T-cell
receptor-dependent and T-cell receptor-independent thymocyte proliferation
AM Stewart-Akers, JS Cairns, DJ Tweardy and SA McCarthy
Department of Molecular Genetics and Biochemistry, University of
Pittsburgh, PA 15213.
The effects of granulocyte-macrophage colony-stimulating factor (GM- CSF)
are not confined to cells of the myeloid lineage. GM-CSF has been shown to
have effects on mature T cells and both mature and immature T- cell lines.
We therefore examined the GM-CSF responsiveness of murine thymocytes to
investigate whether GM-CSF also affected normal immature T lymphocytes. The
studies presented here indicate that GM-CSF augments accessory cell
(AC)-dependent T-cell receptor (TCR)-mediated proliferation of unseparated
thymocyte populations. To identify the GM- CSF responsive cell type, thymic
AC and T cells were examined for GM- CSF responsiveness. We found that
GM-CSF augmentation of TCR-induced thymocyte proliferation appears to be
mediated via augmentation of AC function, and not via direct effects on
mature single-positive (SP) thymocytes. Enriched double-negative (DN)
thymocytes were also tested for GM-CSF responsiveness. GM-CSF induced the
proliferation of adult and fetal DN thymocytes in an AC-independent and
TCR-independent single- cell assay. Thus, in contrast to the SP thymocytes,
a DN thymocyte population was directly responsive to GM-CSF. GM-CSF
therefore may play a direct role in the expansion of DN thymocytes and an
indirect role in the expansion of SP thymocytes.
Volume 83,
Issue 3,
pp. 713-723,
02/01/1994
Copyright © 1994 by The American Society of Hematology
