Germinal Centers and the B-Cell System: B Cell Differentiation in Rabbit Appendix Germinal Centers

Abstract

Recently a choice of B cell differentiation models has become available (1,2,3). In general, peripheral mature (a.o. surface immunoglobulin- and complement receptor-bearing) B cells are thought to derive from relatively undifferentiated though committed (containing cytoplasmic IgM, no surface markers) pre-B cells as present in the bone marrow (4,5). Usually this process is considered to be antigen independent and to occur also in germfree animals (6). Antigen dependent B cell differentation is mainly restricted to terminal differentiation of mature B cells (antibody forming cell precursors, AFCP’s) into actually antibody forming cells (AFC’s or plasmacells). In some instances, however, (7,8) it is suggested that antigen may also be instrumental in the earlier stages of B cell maturation, and there are some indications that spleen B cells from germfree animals cannot do all the tricks that B cells from conventionally reared animals can, i.e. respond to LPS stimulation by polyclonal antibody formation (9). It should be noted that due to a lack of antigenic stimulation germfree animals are also germinal center free (10).