The time-course of differentiation/proliferation
of mast cells in gut epithelium was investigated in mice infected with
the
nematode Strongyloides venezuelensis. After infection, expression
of proliferating cell nuclear antigen increased in gut
intraepithelial mast cells on days 7 to 11, followed by an increase
in the number of intraepithelial mast cells from days 11
to 14. Mast cell precursors were defined as cells that formed mast
cell colonies in methylcellulose culture. After infection,
the numbers of mast cell precursors in the population of gut
intraepithelial mononuclear cells (IEMNC) increased
significantly on day 3 and returned to the pre-infection level by
day 7. Mast cell precursors in Peyer's patches, mesenteric
lymph nodes (MLN), and spleen also increased from day 7 p.i.
Production of IL-3 and IL-4 in MLN and spleen were
increased between 7 and 11 days p.i. These results show that
murine intestinal mastocytosis is initiated by an early increase
in mast cell precursor number in the gut epithelium followed
by proliferation/differentiation of mast cells. Mast cell
precursor numbers increased even before the production of
IL-3 and IL-4 in MLN and spleen, suggesting that some local
factors might be involved in this phenomenon.