SECRETION OF CYTOKINES (INTERLEUKIN-1-ALPHA, INTERLEUKIN-3, AND INTERLEUKIN-6 AND GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR) BY NORMAL HUMAN BONE-MARROW MEGAKARYOCYTES
C. Wickenhauser et al., SECRETION OF CYTOKINES (INTERLEUKIN-1-ALPHA, INTERLEUKIN-3, AND INTERLEUKIN-6 AND GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR) BY NORMAL HUMAN BONE-MARROW MEGAKARYOCYTES, Blood, 85(3), 1995, pp. 685-691
The effects of cytokine stimulation [recombinant human interleukin (rh
IL)-1 alpha, rhIL-3, rhIL-8, rhIL-11, and rh granulocyte-macrophage co
lony-stimulating factor (GM-CSF)] on the secretory activity of normal
human megakaryocytes were studied by means of the reverse hemolytic pl
aque assay (RHPA) in enriched cell preparations. This test facilitates
an extremely sensitive determination of cytokine secretion at the sin
gle-cell level, together with the clear-cut identification of each imm
unostained (CD61) secretory active megakaryocyte. Moreover, the revers
e transcriptase-polymerase chain reaction (RT-PCR) was used to investi
gate the expression of IL-6, IL-6 receptor (IL-6R), IL-9, IL-10, IL-12
, and IL-13 mRNA in highly concentrated megakaryocyte preparations. In
comparison with the spontaneous secretion rate, stimulation with rhIL
-1 alpha, rhIL-6, and rhGM-CSF failed to induce a significant increase
in the release of cytokines by CD61(+) cells. On the other hand, both
rhIL-8 and, in a less pronounced way, rhIL-11 exerted a marked effect
on IL-6 secretion. Additionally, after stimulation with rhIL-3, a sig
nificant enhancement of the secretion of IL-3 and GM-CSF, but not of I
L-1 alpha, could be observed. Using the RT-PCR, a significant inductio
n of IL-6 expression could be appreciated in the enriched megakaryocyt
e population (60% to 80%) stimulated with rhIL3. The results of this s
tudy provide persuasive evidence that a number of cytokines are synthe
sized and secreted by human megakaryocytes and not only by hematopoiet
ic stroma cells. These data suggest the existence of autocrine and par
acrine mechanisms that may influence maturation and differentiation of
megakaryocytes as well as act on various stroma cells to sustain an a
ppropriate hematopoietic microenvironment. (C) 1995 by The American So
ciety of Hematology.