Bs. Wilkins et al., EXTRAMEDULLARY HEMATOPOIESIS IN FETAL AND ADULT HUMAN SPLEEN - A QUANTITATIVE IMMUNOHISTOLOGICAL STUDY, Histopathology, 24(3), 1994, pp. 241-247
Haemopoietic cells were assessed in spleens from normal adults, adults
with splenic extramedullary haemopoiesis due to chronic myeloprolifer
ative disorders and fetuses of 17-21 weeks' gestation. A variety of an
tigens expressed by developing granulocytes and erythrocytes were demo
nstrated immunohistochemically. The relative proportions of early and
late precursor cells of these two lineages were quantified. There was
no significant haemopoiesis in normal adult spleen, while there was ab
undant (predominantly granulocytic) haemopoiesis in patients with chro
nic myeloproliferative disorders. Fetal spleens contained numerous lat
e erythroid precursors but few early erythroid or granulocytic cells.
The relative numbers of early and late haemopoietic cells in adult chr
onic myeloproliferative disorders and fetal spleens showed statistical
ly significant differences. Our findings indicate that haemopoiesis in
the spleens of adult patients with these disorders differs fundamenta
lly from that occurring in fetal life. They support the view that the
human spleen does not have a significant role in fetal haemopoiesis, b
ut that it filters circulating nucleated erythroid precursors and is p
ermissive of their terminal differentiation only. Our results also fav
our the view that adult splenic haemopoiesis originates by displacemen
t of precursor cells from the bone marrow rather than by activation of
stem cells which have lain dormant in the spleen since fetal life.