Histophysiology of follicular structures and germinal centres in relation to B cell differentiation.

A historical review of germinal centres since their original description in 1885 by Flemming is given, followed by a description of the germinal centre reaction. Microenvironmental aspects are discussed, special attention being paid to the role of antigen in the induction and further regulation of germinal centre activity. Germinal centres give rise to a new population of lymphocytes (germinal centre-derived cells). Their immune capacities were studied using the rabbit appendix as an experimental model. The possible properties of the cell from which a germinal centre develops (germinal centre precursor cell) were investigated using germinal centre cell suspensions from the rabbit appendix and bone marrow and thoracic duct lymphocytes in the rat in adoptive transfer systems. From these experiments a working hypothesis was formulated for the possible role of germinal centres in B cell differentiation. Essentially, germinal centres are thought not only to be sites of selective amplification of antigen-reactive but still immature B cells, resulting in the generation of memory cells, but also to contribute to the overall pool of B cells by polyclonal amplification of B cells of specificities unrelated to the antigen inducing the germinal centre.