Abstract
The CD180, a cell surface receptor of lipopolysaccharide (LPS) and a homologue of Toll-like 4(TLR4) on B lymphocyte, has been revealed as suppressing molecule of radiation-induced apoptosis in vitro. However, few studies regarding the functional mechanism of the CD180 molecule associated with radiation-induced apoptosis have been reported in vivo. In the present study, we have examined the effect of irradiation on the expression patterns of CD180 and apoptosis of spleen cells associated with the expression of CD19 and CD22 in vivo. BALB/c female mice (7-8 weeks) were irradiated with X-rays at 150 kVp and 20 mA at a dose rate of 5.4 Gy/m. Spleens were removed after whole body 4 Gy-irradiation. Histochemical analysis demonstrated that the number of CD180 positive- B lymphocytes was significantly increased at 6 h after irradiation when compared with both 3 h after irradiation and 0 h (sham irradiation), irrespective of no significant change of the numbers of B lymphocytes positive for CD19 or CD22 after irradiation for 0 h, 3 h, and 6 h. To clarify the relationship of the expression patterns between apoptosis and CD180, double staining for TUNEL and CD180 was performed and results showed that the number of CD180-negative cells undergoing apoptosis was less than that of CD180-positive cell undergoing apoptosis at 6 h after irradiation. These results suggested that CD180-positive B lymphocytes were resistant to apoptosis induced by irradiation in vivo.
