B220 is Expressed on Apoptotic Thymocytes Induced by X-Irradiation

抄録

CD45 is cell surface glycoprotein and expressed on all haematopoietic cells except mature erythrocytes and platelets. Eight isoforms of CD45 are generated by alternative splicing of exons 4-6. B220 including all three exons is expressed specifically on pan-B cell lineage. Recently, it was reported that B220 was expressed on apoptotic T cells induced by staphylococcal enterotoxin B (SEB). In the present study, we investigated the expression of B220 on murine thymocytes after whole-body X-irradiation. We used the forward light scattering of flow cytometry as a parameter of cell size, and defined two populations; FSC^high (normal cell size) and FSC^low (correspond to apoptotic cell in size) fraction. B220⁺ cells in FSC^high fraction reached a maximum value (35%) at 18 hr after irradiation. In FSC^low fraction, 40-60% cells were positive for B220 at any time points. These results suggest that B220 is expressed on thymocytes in the pre-apoptotic stage, because B220 was expressed on not only FSC^low cells but also FSC^high cells.