A Matter of FACS: Constituting Novel Entities in Immunology

This article contributes to the development of an anthropology of biomedicine that takes as its subject matter the content of biomedical knowledge and practices. It offers an ethnographic account of the establishment of the international classification of white blood cells, known as the “CD nomenclature,” and goes beyond the assertion that biomedical knowledge is “socially constructed,” providing a fine‐textured analysis of how, in this specific case, knowledge was constituted. The CD nomenclature found its way into newspapers and daily medical practice mainly through the involvement of the CD4 subclass of lymphocytes (white blood cells) in AIDS definition and diagnosis. The establishment of the CD nomenclature is thus part of the recent movement of immunology to the center stage of the biomedical sciences. This study analyzes the articulation of the elements (institutions, tools, concepts) that made the classification possible. By focusing on the material practices of immunologists, the analysis shows that the present‐day classification of lymphocytes has as its precondition the constitution of a network for the establishment of identities between immunological reagents produced by different laboratories. Furthermore, it is argued that the standards by which identities are established are inseparable from the entities (lymphocyte subsets) that are classified. Finally, it is claimed that an ethnography of the practices by which such a network comes into being provides an adequate analysis of the constitution of knowledge, specifically, of scientific information about the entities known as lymphocyte subsets.