Investigations of 'transfer factor' activity in the transfer of immunity to Trichostrongylus axei infections in sheep.

Three investigations are described in which non-dialysed and dialysed leucocyte lysates, 'transfer factor' prepared from the blood of sheep infected with Trichostrongylus axei successfully transferred immunity to challenge infection with that parasite in susceptible lambs. Similar leucocyte lysates from parasite-free lambs failed to transfer a similar resistance to challenge infection. 'Transfer factor' treatment produced a 30--72 per cent reduction in a total worm burden compared to susceptible control lambs. In the first two investigations the donor and recipient lambs were genetically dissimilar and in the third investigation were of different breeds. The resistance transfer was considered to operate independently of immune incompetence.