B cell mitogenic activity of Toxocara canis adult worm antigen.

The effect of Toxocara (T.) canis antigen (TcAg) on lymphocytes was studied in vitro using normal murine spleen cells and human peripheral blood lymphocytes. TcAg prepared from adult worms stimulated murine spleen cells to proliferate at concentrations of 1-125 micrograms/ml. The responder cells TcAg are B cells, because the response was depleted by the treatment of spleen cells with anti-immunoglobulin (Ig) antibody and complement and after separation on a nylon wool column. This response was not due to the contamination of lipopolysaccharide (LPS), because TcAg could stimulate C3H/HeJ spleen cells which are low responders to LPS. Not only the proliferative response but also polyclonal IgG and IgE production were stimulated with TcAg. TcAg also stimulated macrophages to produce interleukin-1 and could stimulate human B cells. These results suggest that TcAg is a potent B cell mitogen and this activity may be relevant to the alteration of immunological functions in hosts infected with T. canis.