1. Burridge, M.J., Morzaria, S.P., Cunningham, M.P. & Brown, C.G.D. (1972) Parasitology
64, 511.
2. Cikes, M., Friberg, S. Jr. & Klein, G. (1973) J. Natl. Cancer Inst. 50, 347.
3. Emery, D.L. (1981) Res. vet. Sci., in press.
4. Emery, D.L., Eugui, E.M., Nelson, R.T. & Tenywa, T. (1981) Imnunology, in press.
5. Eugui, E.M. & Emery, D.L. (1981) Nature, in press.