The effects of Fasciola hepatica tegumental antigens on mast cell function

Fasciola hepatica infection is associated with T helper 2/T regulatory immune responses and increased mast cell numbers. The aim of this study was to examine the interaction between F. hepatica tegumental coat antigen and mast cells in vivo and in vitro. Firstly, BALB/C, C57BL/6 or STAT6(-/-) mice were infected with F. hepatica metacercarie or mice were treated with F. hepatica tegumental coat antigen and then mast cells numbers in the peritoneal cavity and/or the liver were quantified. Also, the proliferation, chemotaxis, degranulation and cytokine secretion of mast cells from bone marrow or from peritoneal exudate cells stimulated with F. hepatica tegumental coat antigen were measured. Finally, we tested whether F. hepatica tegumental coat antigen inhibits degranulation of mast cells in vivo in a passive cutaneous and systemic anaphylaxis mouse model. Mast cell numbers increased in the peritoneal cavity and liver of F. hepatica infected mice, and this was mimicked by injection of F. hepatica tegumental coat antigen in a STAT6(-/-) independent manner. The increase in mast cell number was not the result of F. hepatica tegumental coat antigen-induced proliferation; rather F. hepatica tegumental coat antigen indirectly induces mast cell migration by dendritic cell-derived chemokines. Fasciola hepatica tegumental coat antigen interactions with mast cells do not drive T helper 2 or T regulatory immune responses. These studies on mast cell and F. hepatica tegumental coat antigen interaction may help us to understand the function of mast cells in immunity against F. hepatica and the immunomodulatory effect of F. hepatica tegumental coat antigen on these cells.