Dynamic changes of B‐cell compartments in kidney transplantation: lack of transitional B cells is associated with allograft rejection

Abstract B cellsplay an important role in the immune responses which affect the outcomes of kidney allografts. Dynamic changes of B-cellcompartments in clinical kidney transplantationare still poorly understood. B-cellsubsets were prospectively monitored using flow cytometry for 1 year in 98 kidney transplantrecipients. Data were correlated with immunosuppression and clinical outcomes. An increase in the total population of B lymphocytes was observed during the first week after transplantation. The level of IgM(high) CD38(high) CD24(high) transitional B cellsreduced significantly up until the third month, with partial repopulationin the first year. Lower numbers of transitional B cellsin the third month were associated with higher risk of graft rejection. IgM(+) IgD(+) CD27(-) naive B cellsdid not change within follow-up. IgM(+) CD27(+) nonswitched memory B cellsand IgM(-) CD27(+) switched memory B cellsincreased on post-operative day 7. IgM(-) CD38(high) CD27(high) plasmablasts showed similar kinetics during the first post-transplant year, similar to transitional B cells. In conclusion, sensitized kidney transplantrecipients as well as those with either acute or chronic rejection within the first post-transplant year exhibited lower levels of transitional B cells. Therefore, these data further support the hypothesis that transitional B cellshave a protective role in kidney transplantation.