Plasma cell toll-like receptor (TLR) expression differs from that of B cells, and plasma cell TLR triggering enhances immunoglobulin production.

Toll-like receptors (TLRs) are key receptors of the innate immune system and show cell subset-specific expression. We investigated the messenger RNA (mRNA) expression of TLR genes in human haematopoietic stem cells (HSC), in naïve B cells, in memory B cells, in plasma cells from palatine tonsils and in plasma cells from peripheral blood. HSC and plasma cells showed unrestricted expression of TLR1-TLR9, in contrast to B cells which lacked TLR3, TLR4 and TLR8 but expressed mRNA of all other TLRs. We demonstrated, for the first time, that TLR triggering of terminally differentiated plasma cells augments immunoglobulin production. Thus, boosting the immediate antibody response by plasma cells upon pathogen recognition may point to a novel role of TLRs.