Finding a home for plasma cells--a niche to survive.

Long-term survival of plasma cells (PCs) and sustained antibody secretion require a specific microenvironment that provides the appropriate prosurvival signals. This plasma cell niche involves both mesenchymal and hematopoietic components. Although a consensus exists about the essential contribution of CXCL12(+) stromal cells in this environment, the identity of the hematopoietic participants remains a matter of debate. In this issue of the European Journal of Immunology, Zehentmeier et al. [Eur. J. Immunol. 2014. 44: 2306-2317] aim to identify the components of the bone marrow plasma cell niche in C57BL/6 mice in an unbiased manner by using a streamlined analysis of histological colocalization data. Apart from stromal cells, the authors showed that eosinophils are the only population specifically localized in the vicinity of PCs. In addition, the authors performed intravital imaging demonstrating that PCs are sessile and form stable contacts with reticular stromal cells. This work opens the door to a more rational approach to characterize the plasma cell niche.