The 55th Nobel Symposium entitled "Genetics of the Immune Response" took place in Saltsjobaden, Sweden, June 15 - 17, 1982. The topic was selected for several reasons, such as the rapid progress in the genetic analysis of immunoglobulin and MHC genes and the elucidation of the mechanism of switch to different immunoglobulin classes and subclasses. The genetic advances formed a basis for discussions of problems relating to regulation of T cell subsets, mechanisms of activation and regulation of B cell differentiation and an analysis of the network hypothesis. The format of the symposium was arranged so as to include two sessions in the morning and two in the afternoon. Each session was introduced by one speaker, followed by free discussion. The intro ductory lectures are included in the proceedings. The participants summarized their contributions to the discussion in written form. In addi tion to the closed sessions, there was one open session at the Karolinska Institute with lectures by Drs. L. Hood, C. Milstein, D. Baltimore, J. Klein and B. Benacerraf, which are not included in these procee din gs. The symposium was sponsored by the Nobel Foundation and its Nobel Symposium Committee through grants from the Tercentenary Fund of the Bank of Sweden and the Knut & Alice Wallenberg Foundation. The Swedish Medical Research Council, the Swedish Cancer Society and the Swedish Ministry of Education and Cultural Affairs also made contri butions."

This volume deals with the structure and function of molecules that have, during the last decade, turned out to have a central role in immune responses. Trans plantation antigens were discovered and characterized by Gorer about 50 years ago, and the biological basis for the unequalled complexity of their variability between individuals within a species, in spite of extreme conservation between species, was the subject of intense research and discussion for many years. During the days of belief in "immune surveillance" against spontaneously developing tumors, it was suggested that histoincompatibility between members of one species would prevent cancer from being a contagious disease and thus a threat to the species. Immunologists involved in human transplantation had to learn and care about the complexity, especially after 1967, when it was found that HLA antigens were the products of the human MHC. Rejection of HLA-identical sib kidney grafts was so rare, even in those days, that cases of rejection were described in scientific papers."