No strict requirement for eosinophils for bone marrow plasma cell survival

Lasting antibody responses are maintained by long‐lived plasma cells, which are thought to lodge in the BM in specialized survival niches. Eosinophils have been reported to function as a critical component of the BM survival niche where they are thought to provide pro‐survival signals to nearby plasma cells. Recent study shows that many BM plasma cells are recently generated and chiefly short‐lived cells, raising the possibility that rare plasma cell–eosinophil interactions are a rate‐limiting step needed to establish lasting humoral immunity. To address these issues, we examined the impact of eosinophil depletion on short‐ and long‐lived BM plasma cells in the context of antibody responses induced by both T‐cell dependent and T‐cell independent antigens. Surprisingly, our results failed to support a role for eosinophils in either plasma cell generation or survival. These studies included examination of plasma cell frequencies in mice lacking eosinophils either after antibody‐mediated depletion, or due to mutation of the GATA1 locus. Depletion of eosinophils with antibodies or by genetic manipulation has no appreciable effect on the mature or immature plasma cell pools in the bone marrow, suggesting that plasma cells receive survival signals from multiple redundant sources.