Comparative gene expression profiles of T-dependent and T-independent germinal centre B cells in mice

Selection of B cells subjected to hypermutation in germinal centres (GC) during T-dependent (TD) antibody responses yields memory cells and long-lived plasma cells that produce high affinity antibodies biased to foreign antigens rather than self-antigens. GC also form in T-independent (TI) responses to polysaccharide antigens but failed selection results in GC involution and memory cells are not generated. To date there are no markers that allow phenotypic distinction of T-dependent and T-independent germinal centre B cells. We have now compared the global gene expression of GC B cells purified from mice immunized with either TD or TI antigens and identified eighty genes that are differentially expressed in TD GC. Keywords: T-dependent and T-independent germinal center B cells QMxB6 F1 mice were immunised with T-independent antigens (NP-Ficoll) or T-dependent antigens (NP-CGG). T-dependent responses were analysed in carrier primed mice and non-carrier primed mice. The kinetics in carrier primed mice are comparable to those of TI-2 antigens, and thus, both of these groups were analysed 4 days after immunization with soluble antigen. The response in non-carrier primed mice peaks later, and was therefore analysed on day 10 after immunization. Germinal centre B cells were MACS enriched and then FACS sorted according to GL-7 and B220 expression. Sorted B cells from the relevant mice were pooled (4-10 mice per sample). Each sample thus contains B cells from different mice, and the replicates are biological, not technical replicates.