1. Lanzavecchia, A. Nature 314, 537 (1985).
2. Paul. W.E. (Ed.) Fundamental Immunology (Raven, New York, 1984).
3. Hood, L.E., Weissman, I.L., Wilson, J.H. & Wood, W.B. Immunology 2nd edn (Benjamin-Cummings, 1984).
4. Mitchison, N.A. Eur. J. Immun. 1, 18 (1971).
5. Katz, D.H., Hamaoka, T., Dorf, M.E., Maurer, P.H. & Benacerraf, B. J. exp. Med. 138, 734 (1973).