PROTECTIVE EFFECT OF ADMINISTRATION OF SKIM MILK ON EXOGENOUS AND ENDOGENOUS INFECTION IN MICE

In order to minimize the denaturation of proteins in milk, normal cow' s milk was pasteurized at 61 C for 20 min. The protective effects of t he thus prepared skim milk (low-heat skim milk) on exogenous and endog enous infection were examined as compared with conventional skim milk which was pasteurized at 121 C for 2 sec. The antibody titers to Liste ria monocytogenes and Escherichia coli of low-heat skim milk were almo st equal to that of raw milk, while no antibody was detected in the co nventional skim milk. When mice were given low-heat skim milk or conve ntional skim milk, the incidence of the translocation of orally inocul ated Listeria monocytogenes to the spleen was lower in the low-heat sk im milk group than that in the conventional skim milk group. The life span of 7 Gy X-ray irradiated mice given low-heat skim milk was signif icantly prolonged in comparison to that of mice given conventional ski m milk. However, there were no differences in the number of bacteria i n the feces or IgA production by Peyer's patch cells between the two g roups. These results suggest that antibodies in low-heat skim milk, wh ich still have reactivity to exogenous or indigenous bacteria, may con tribute to the protective effects against bacterial infection.