Acknowledgment
We thank Mr. Semba in Division of Laboratory Medicine, Chiba University Hospital for technical assistance on flow cytometric analysis.
Disclosure statement
No potential conflict of interest was reported by the authors.
Authorship contributions
Y.N. and S.T. wrote the manuscript; C.N. and E.S. reviewed and revised the manuscript; Y.I. and M.Y. supported flow cytometric analysis; and Y.H., S.I., T.M., N.O-H., S.M., Y.T., N.M., M.T., C.O., T.I. participated in acquisition of data and interpretation of data.