Identification of Ly-6K as a novel marker for mouse plasma cells.

Plasma cells are the main producers of antibody and key effector cells of the immune system. Despite their importance, analytics of plasma cells still suffers from the limited availability of specific markers. Currently, plasma cell identification relies on the expression of a single marker, CD138/syndecan-1. However, syndecan-1 is widely expressed on various cell types outside the hematopoietic compartment, and furthermore, not expressed on all subsets of plasma cells. To discover novel surface markers, a differential screening followed by signal sequence trap cloning was developed, leading to the identification of mouse Ly-6K (mLy-6K). Expression profiling confirmed that mLy-6K is expressed by plasma cells but not B cells or tissues not containing plasma cells. Expression at the surface of plasma cells isolated from spleen, lymph node, bone marrow, and lamina propria of the small intestine was demonstrated at the protein level using a polyclonal rabbit antibody. This novel plasma cell marker shows promise to help broaden our understanding of plasma cell differentiation and function.