TLR1/2, TLR7, and TLR9 Signals Directly Activate Human Peripheral Blood Naive and Memory B Cell Subsets to Produce Cytokines, Chemokines, and Hematopoietic Growth Factors

Recently, it has been reported that using multiple signals, murine and human B cells secrete several cytokines with pro-inflammatory and immunoregulatory properties. We present the first comprehensive analysis of 24 cytokines, chemokines, and hematopoietic growth factors production by purified human peripheral blood B cells (CD19+), and naive (CD19+CD27-) and memory (CD19+CD27+) B cells in response to direct and exclusive signaling provided by toll-like receptor (TLR) ligands Pam3CSK (TLR1/TLR2), Imiquimod (TLR7), and GpG-ODN2006 (TLR9). All three TLR ligands stimulated B cells (CD19+) to produce cytokines IL-1 alpha, IL-1 beta, IL-6, TNF-alpha, IL-13, and IL-10, and chemokines MIP-1 alpha, MIP-1 beta, MCP-1, IP-10, and IL-8. However, GM-CSF and G-CSF production was predominantly induced by TLR2 agonist. Most cytokines/chemokines/hematopoietic growth factors were predominantly or exclusively produced by memory B cells, and in general, TLR2 signal was more powerful than signal provided viaTLR7 and TLR9. No significant secretion of eotaxin, IFN-alpha, IFN-gamma, IL-2, IL-3, IL-4, IL-5, IL-7, IL-15, IL-17, IL-12p40, IL-12p70, and TNF-beta (lymphotoxin) was observed. These data demonstrate that human B cells can be directly activated viaTLR1/TLR2, TLR7, and TLR9 to induce secretion of cytokines, chemokines, and hematopoietic growth factors and suggest a role of B cells in immune response against microbial pathogenesis and immune homeostasis.