Characterization of B cell subsets in cynomolgus monkeys

Plasma cells are believed to play a prominent role in the pathogenesis of autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus. In support of biomarker identification for B‐cell‐targeted therapies, we used an intracellular FACS‐based assay for the endoplasmic reticulum (ER)‐associated plasma cell marker PC (VS38c) and intracellular immunoglobulin to characterize plasma cells in non‐human primates. We identified two distinct subsets of PC‐expressing cells in cynomolgus monkey spleen – a population that expresses high levels of PC and IgG or IgM (PChighIghigh), and another subset that expresses intermediate levels of PC and IgG (PCintIgGint). Similar to human CD138+ plasma cells, the PChigh and PCint populations do not express CD20, express low levels of the BAFF receptor‐3 (BAFF‐R, BR3), and appear to be larger and more granular than PCneg B‐cells. There are increased percentages of Ki67+ proliferating cells in the PChighIgGhigh subset compared to the PCintIgGint population. The characterization of plasma cell populations in non‐human primates will expand our knowledge of B‐cell development and contribute to the development of novel therapies for autoimmune and inflammatory diseases.