A Possible Effect of Oral Tolerance in Casein Induced Murine Amyloidosis?

Abstract

Mice raised on a normal mouse chow diet have a low immune response to immunization with casein. In addition, attempts to experimentally induce oral tolerance with casein in mice raised on a normal diet failed. Normal mouse chow contains substantial casein as a protein source. However, when mice were raised on a casein free diet and immunized with casein they had 4–5× the immune response of the normal diet mice. If such casein free mice were fed casein experimentally and then immunized the immune response was markedly suppressed. Thus mice raised on normal mouse chow are orally tolerized by the casein it contains, and this accounts for the low immune responses to casein previously reported. There are conflicting reports regarding the effect of neonatal parenterally induced tolerance to casein on susceptibility to amyloidosis, but no reports have ever considered a possible role of dietary induced tolerance in interpreting the results, a phenomenon which might well be a variable in different studies. In fact we found that one of the so called “tolerizing” protocols actually immunized the mice and prevented the development of oral tolerance due to the dietary casein. This raises the intriguing possibility that oral tolerance may be a susceptibility factor in amyloidosis.