Exercise-induced B cell mobilisation: Preliminary evidence for an influx of immature cells into the bloodstream.

The number of peripheral blood B lymphocytes doubles during acute exercise, but the phenotypic composition of this response remains unknown. In two independent exercise studies, using complimentary phenotyping strategies, we investigated the mobilisation patterns of distinct B cell subsets. In study one, nine healthy males (mean±SD age: 22.1±3.4years) completed a continuous cycling bout at 80% V̇O2MAX for 20min. In study two, seven healthy experienced cyclists (mean±SD age: 29.9±4.7years) completed a 30min cycling trial at a workload corresponding to +5% of the individual blood lactate threshold. In study one, CD3-CD19+ B cell subsets were classified into immature (CD27-CD10+), naïve (CD27-CD10-), memory (CD27+CD38-), plasma cells/plasmablasts (CD27+CD38+) and finally, recently purported 'B1' cells (CD27+ CD43+ CD69-). In study two, CD20+ B cells were classified into immature (CD27-IgD-), naïve (CD27-IgD+), and IgM+/IgG+/IgA+ memory cells (CD27+IgD-). Total B cells exhibited a mean increase of 88% (study one) and 60% (study two) during exercise. In both studies, immature cells displayed the greatest increase, followed by memory cells, then naïve cells (study one: immature 130%>mature 105%>naïve 84%; study two: immature 110%>mature 56%>naïve 38%). Our findings show that, unlike T cells and NK cells, B cell mobilisation is not driven by effector status, and, for the first time, that B cell mobilisation during exercise is comprised of immature CD27- IgD-/CD10+ cells.