The receptor tyrosine kinase MerTK regulates dendritic cell production of BAFF

Abstract

The MerTK receptor tyrosine kinase is an important negative regulator of dendritic cell function and is required to prevent B cell autoimmunity in vivo. It is not currently known however, if any causal relationship exists between these two aspects of MerTK function. We sought to determine if dendritic cells (DC) from mice lacking MerTK (mertk^{− / −} mice) have characteristics that may aid in the development of B cell autoimmunity. Specifically, we found that mertk^{− / −} mice contain an elevated number of splenic DC, and this population contains an elevated proportion of cells secreting the critical B cell pro-survival factor, B cell activating factor (BAFF). Elevated numbers of BAFF-secreting cells were also detected among mertk^{− / −} bone marrow-derived dendritic cell (BMDC) populations. This was observed in both resting BMDC, and BMDC stimulated with lipopolysaccharide (LPS) or treated with exogenous apoptotic cells. We also found that DC in general have a pro-survival effect on resting B cells in co-culture. However, despite containing more BAFF-secreting cells, mertk^{− / −} BMDC were not superior to C57BL/6 or baff-deficient BMDC at promoting B cell survival. Furthermore, using decoy receptors, we show that DC may promote B cell survival and autoimmunity through a BAFF-and a proliferation-inducing ligand-independent mechanism.

• MerTK
• BAFF
• dendritic cell
• autoantibody
• B cell survival

Acknowledgements

We thank Dr. Susan Kalled (Biogen Idec) for review of this manuscript. This work is supported by NIAID AI50736.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.