Expressions of CD180 on Spleen cells induced Apoptosis by X-ray-irradiation

The CD180, a cell surface receptor of lipopolysaccharide (LPS) and ahomologue of Toll-like 4(TLR4) on B lymphocyte, has been revealed as asuppressing molecule of radiation-induced apoptosis in vitro and as aphysiological negative regulator of TLR4 responses. However, few studiesregarding the functional mechanism of the CD180 molecule associated withradiation-induced apoptosis have been reported in vivo. In the presentstudy, we have examined the effect of irradiation on the expression patternsof CD180 and apoptosis of spleen cells associated with the expression ofCD19 and CD22, B-cell signal transduction molecules, in vivo. BALB/c femalemice (7-8 weeks) were irradiated with X-ray machine operated at 150 kVp and20 mA at a dose rate of 5.4 Gy/m. Spleens were removed after wholebody-irradiation. Histochemical analysis demonstrated that the number ofCD180-positive B lymphocytes was significantly increased at 6 h afterirradiation compared with that in both 3 h and 0 h (sham irradiation),whereas no significant change of the numbers of B lymphocytes positive forCD19 or CD22 was detected at 0 h, 3 h, and 6 h after irradiation. Flowcytometric analysis of the spleen cells showed that the percentage ofCD180-presenting cells increased at 6 h after irradiation than that at 0 h.The expression of CD180 was increased dependently on radiation dose from 0Gy to 10 Gy with histochemical analysis. To clarify the relationship of theexpression patterns between apoptosis and CD180, double staining for TUNELand CD180 was performed and showed that the number of CD180-positive cellspositive for TUNEL was significantly less than that of CD180-negative cellspositive for TUNEL at 6 h after irradiation. These results suggested thatCD180-positive B lymphocytes were resistant to apoptosis induced byirradiation in vivo.第38回日本免疫学会総会・学術集