The effects of liquid culture filtrates of medicinal entomogenous fungi, Paecilomyces tenuipes (Peck) Samson (=Isaria japonica Yasuda or Isaria tenuipes) (PTCF) and Paecilomyces cicadae (Miquel) Samson (=Isaria sinclairii (Berk.) Llond) (PCCF), on cytokine productions in cultured Peyer's patches (PP) from C57BL/6J mice were investigated in vitro and ex vivo. In an in vitro experiment, PTCF (100 and 10 microg/ml) enhanced the production of T helper 1 (Th1) cytokines, interleukin (IL)-2 and interferon (IFN)-gamma, in cultured PP cells stimulated with 5 microg/ml concanavalin A (Con A) but did not influence on the production of T helper 2 (Th2) cytokines, IL-4 and IL-5. PTCF also enhanced the production of granulocyte macrophage colony-stimulating factor (GM-CSF) and IL-10 in the cultured PP cells. While, PCCF enhanced the production of IFN-gamma but did not alter the level of IL-2 in the PP cells. In an ex vivo experiment using PP cells removed from the mice after oral treatment of PTCF (10 and 100 mg/kg daily for 7 consecutive days), the production of IL-2 and IFN-gamma were increased in response to Con A. On the other hand, orally treated PCCF (10 mg/kg/day) suppressed IL-2 production but did not change the levels of IFN-gamma and IL-10 in the isolated PP cells. The flow cytometric analysis revealed that the population of CD3(+) cells in the PP cells slightly but significantly increased after oral administration of PCCF. Orally administered PTCF did not change the population of T (CD3(+)), B (CD19(+)), T cell subset (CD4(+)and CD8(+)) and Th1 (IFN-gamma(+)) and Th2 (IL-4(+)). From PTCF, the fraction rich in proteoglycans was separated as active fraction that stimulates Th1 immune response. These results indicate that the mode of action of PTCF and PCCF on mucosal immune response is different and this is contributed to their metabolites. Taken together, there is a possibility of PTCF and PCCF being therapeutic or preventive agents for immune diseases such as cancer, allergy and parasitic disease through activation of mucosal immune response.