The Journal of Immunology, Vol 137, Issue 8 2508-2513, Copyright © 1986 by American Association of Immunologists
The influence of T lymphocyte subsets and humoral factors on colony formation by human bone marrow and blood megakaryocyte progenitor cells in vitro
D Geissler, L Lu, E Bruno, HH Yang, HE Broxmeyer and R Hoffman
Cellular and humoral influences of T lymphocytes on human megakaryocyte
colony formation in vitro were assessed by using a microagar system.
Megakaryocyte colony formation from nonadherent low density T
lymphocyte-depleted (NALDT-) bone marrow cells was increased significantly
after the addition of aplastic anemia serum (AAS) or purified megakaryocyte
colony-stimulating factor (Meg-CSF). The addition of conditioned medium
obtained from phytohemagglutinin- stimulated T lymphocytes replaced, at
least partially, the requirement for AAS or purified Meg-CSF for the growth
of megakaryocyte colonies. The cellular influence of T lymphocytes and T
lymphocyte subsets on megakaryocyte colony formation was assessed by
removing either T cells from nonadherent peripheral blood mononuclear cells
with monoclonal OKT4, OKT8, or OKT3 antibodies plus complement, or by
adding back populations of bone marrow or blood T4+ or T8+ lymphocytes,
isolated by means of fluorescence-activated cell sorting, respectively, to
NALDT-- bone marrow or -blood cells. When sorted T cell subpopulations were
added to a fixed number of NALDT--bone marrow or -peripheral blood cells in
the presence of AAS or Meg-CSF, T4+ cells enhanced megakaryocyte colony
formation and T8+ cells decreased it. These studies demonstrate that
although the stimulation of megakaryocytic progenitor cells by Meg-CSF may
not require the presence of monocytes or T lymphocytes, T4+ lymphocytes
enhance and T8+ lymphocytes down- regulate megakaryocyte colony formation
induced by Meg-CSF. These observations suggest that the immune system is
capable of modulating the proliferative response of human megakaryocytic
progenitor cells to Meg-CSF.
