Mice presensitized with SEA and subsequently injected with S. japonicum eggs into their lungs or liver developed pathology similar to that found in infected mice and were consequently resistant to challenge (average 33% and 53%, respectively). However, soluble egg antigens were also capable of inducing low levels of resistance in mice (average 22·5%), but intact eggs alone injected into the lungs, liver or subcutance tissues were not. Thus, prior sensitization to ‘marginally’ protective soluble egg antigens is necessary for egg induced resistance.
