In 1958, just a little more than 50 years ago, an alloantigen present on human leucocytes was detected, which was to become the 'first' human leucocyte antigen (HLA); HLA-A2. Since then, we have seen a tremendous development of the HLA field, which has moved from histocompatibility to become one of the most central fields in basic and clinical immunology. This development is briefly reviewed in this article, focusing on some highlights of the history of HLA class I and II molecules and their role in immune responses. It is emphasized that the quick and extensive development of the HLA field is the result not only of excellent individual contributions by outstanding pioneers in the field, but also of an extensive international collaboration, in particular through the many international histocompatibility workshops. Admitting that it is too late to change the name now, it is concluded that instead of calling the HLA complex and similar complexes in other species the major histocompatibility complex, these gene complexes should better have been named the major immune response complex, the MIRC.