The effects of an
oral administration of BLP, a preparation of viable Lactobacillus casei
YIT 9018, upon
tumor growth and the mitogenic responses of splenocytes from
tumor-bearing mice were studied. BALB/c mice were insufficiently pre-immunized by resecting a Colon 26
tumor mass (primary
tumor) grown for 5 days intradermally. Thereafter, mice were rechallenged by injecting Colon 26
tumor (secondary
tumor) into the hind footpad. The secondary
tumor grew progressively in control mice, but was markedly suppressed by
oral administration with BLP at a dose of 100 or 200 mg/kg/day for 7 consecutive days. The suppression was a primary
tumor-specific response. Viable L. casei, not heat-killed L. casei, could suppress the secondary
tumor. Although the lymphoproliferative responses of splenocytes from the secondary
tumor-bearing mice with T-cell
mitogens (
concanavalin A and phytohaemagglutinin) and
cytokines (interleukin-1 and interleukin-2) were lower than those of normal mice, this suppression of mitogenic responses under
tumor-bearing conditions was abolished by
oral administration with BLP. Thus we concluded that oral BLP potentiated systemic immune responses that modified T-cell functions in
tumor-bearing mice.