STEM-CELL FACTOR-DEPENDENT HYPERPLASIA OF MUCOSAL-TYPE MAST-CELLS BUTNOT EOSINOPHILS IN SCHISTOSOMA-MANSONI-INFECTED RATS

Stem cell factor (SCF) is a growth factor with multiple activities whi ch acts on numerous cell types including primordial germ cells, haemop oietic stem cells, melano-cytes and mast cells. SCF is critical for th e development of the mast cell hyperplasia associated with infection w ith the intestinal parasites Nippostrongylus brasiliensis and Trichine lla 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. R ats treated with sheep anti-SCF antibody on days 21, 24, 27 and 30 of infection with S. mansoni showed a rapid decrease in serum concentrati ons of the mucosal mast cell-associated protease rat mast cell proteas e II (RMCP II) by day 24, compared with normal sheep IgG-treated contr ols. 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 ma st cell proteases, eosinophil numbers in liver or intestine did not ch ange significantly after anti-SCF treatment compared with controls. Th ese results confirm that mast cell survival and hyperplasia are depend ent on the presence of SCF whilst demonstrating that the eosinophil re cruitment to live and intestine associated with S. mansoni infection i s SCF-independent.