Gene expression by human splenic B-cell subsets

Enhanced secondary Ab responses are a vital component of adaptive immunity, yet little is understood about the intrinsic and extrinsic regulators of naïve and memory B cells that results in differences in their responses to Ag. Microarray analysis, together with surface and intracellular phenotyping, revealed that memory B cells have increased expression of members of the TNF receptor, SLAM, B7 and Bcl2 families, as well as the TLR-related molecule CD180 (RP105). Accordingly, memory B cells exhibited enhanced survival, proliferation and Ig secretion, as well as entered division more rapidly than naïve B cells in response to both T-dependent and T-independent stimuli. Furthermore, both IgM and isotype switched memory B cells, but not naïve B cells, co-stimulated CD4+ T cells in vitro through a mechanism dependent on their constitutive expression of CD80 and CD86. This study demonstrates that upregulation of genes involved in activation, co-stimulation and survival provides memory B cells with a unique ability to produce enhanced immune responses and contributes to the maintenance of the memory B cell pool. Keywords: cell type comparison Four subsets of human splenic B cells (naïve, IgM-memory, Ig isotype switched memory and plasma cells); sort-purified and analysed immediately ex vivo; performed in duplicate.