Evidence for melano-macrophage centres of teleost as evolutionary precursors of germinal centres of higher vertebrates: an immunohistochemical study.

The melano-macrophage centres (MMCs) of the haemolymphopoietic organs of teleost fish trap and retain antigens and are closely associated with immunoglobulin-secreting cells. The hypothesis that they are the phylogenetic precursors of the germinal centres of higher vertebrates has been questioned due to their apparent lack of organising cells. In this study the immunoreactivity of MMC cells from spleen and kidney of the teleosts Cyprinus carpio, Odontesthes bonariensis and Solea senegalensis to CNA-42, an antibody usually employed for labelling follicular dendritic cells of higher vertebrates was investigated. Free melano-macrophages and MMCs in the spleens of all three species were labelled by the antibody. This finding adds new evidence to the hypothesis that an evolutionary relationship exists between the MMCs of fish and the germinal centres of many birds and mammals.