In fascioliasis, T-helper 2 (Th2) responses predominate, while little is known regarding early immune phenomenon. We herein analyzed early immunophenotype changes of BALB/c, C57BL/6, and C3H/He mice experimentally infected with 5 Fasciola hepatica metacercariae. A remarkable expansion of CD19(+) B cells was observed as early as week 1 post-infection while CD4(+)/CD8(+) T cells were down-regulated. Accumulation of Mac1(+) cells with time after infection correlated well with splenomegaly of all mice strains tested. The expression of tumor necrosis factor (TNF)-α mRNA in splenocytes significantly decreased while that of IL-4 up-regulated. IL-1β expression was down-modulated in BALB/c and C57BL/6 mice, but not in C3H/He. Serum levels of transforming growth factor (TGF)-β were considerably elevated in all mice during 3 weeks of infection period. These collective results suggest that experimental murine fascioliasis might derive immune suppression with elevated levels of TGF-β and IL-4 during the early stages of infection.