Stem cell factor dependent hyperplasia of mucosal-type mast cells but not eosinophils in Schistosoma mansoni-infected rats.

Stem cell factor (SCF) is a growth factor with multiple activities which acts on numerous cell types including primordial germ cells, haemopoietic stem cells, melanocytes and mast cells. SCF is critical for the development of the mast cell hyperplasia associated with infection with the intestinal parasites Nippostrongylus brasiliensis and Trichinella spiralis. In the present study we have assessed the role of SCF in the mast cell and eosinophil responses to Schistosoma mansoni in the rat by blocking its effects in vivo with polyclonal antibody to SCF. Rats treated with sheep anti-SCF antibody on days 21, 24, 27 and 30 of infection with S. mansoni showed a rapid decrease in serum concentrations of the mucosal mast cell-associated protease rat mast cell protease II (RMCP II) by day 24, compared with normal sheep IgG-treated controls. Similarly, the number of mucosal mast cells and RMCP II levels in both small intestine and liver were also significantly reduced by day 32 of infection. In contrast with the depeletion of mast cells and mast cell proteases, eosinophil numbers in liver or intestine did not change significantly after anti-SCF treatment compared with controls. These results confirm that mast cell survival and hyperplasia are dependent on the presence of SCF whilst demonstrating that the eosinophil recruitment to liver and intestine associated with S. mansoni infection is SCF-independent.