Thymus Antibody-Secreting Cells Represent a Tissue Specific Population That Possess an Activated Cellular Phenotype

Summary Antibody-secreting cells (ASCs) are key contributors to humoral immunity through immunoglobulin production and the potential to be long-lived. ASCs have been recently identified in the thymus (THY) which is of interest as autoreactive THY B cells regulate T cell tolerance. Here, we showed that the young female THY was skewed towards higher production of ASCs relative to males. However, these differences disappeared with age. Intravenous labeling combined with blockade of CD154(CD40L) suggested that THY ASCs were generated in situ in a T cell dependent fashion. Single cell RNA-sequencing revealed that THY ASCs possessed a transcriptional signature indicative of interferon signaling and activation. Flow cytometry confirmed that THY ASCs had increased levels of Toll-like receptor 7 as well as the activation markers CD69 and major histocompatibility class II. Overall, THY ASCs are a unique population that require further investigation to fully appreciate their biological significance.