The process of categorizing the antigenic molecules and epitopes associated with human white cells, via the collaborative study of monoclonal antibodies, dates back to the early 1980s, when the first HLDA (Human Leukocyte Differentiation Antigen) Workshop was held in Paris. This initial meeting listed only 15 agreed molecular entities, but it created an internationally agreed basis for the nomenclature of leukocyte molecules (the CD scheme), and also provided a forum for reporting studies on their function and practical relevance. A further six HLDA meetings have been held since the first Paris meeting. The most recent of these ("HLDA7") took place last year in Harrogate, GB, and the proceedings of the meeting will be published later this year (Leucocyte Typing VII, Oxford University Press).
