When C57BL/6 (B6) mice were irradiated (9Gy) and received bone marrow (BM) cells of B6-
lpr/lpr mouse origin (i.e.,
lpr→B6), all mice died within 6 days. In the irradiated B6 mice, radioresistant CD3
- IL-2Rβ
+ NK cells and IL-2Rβ
+ CD3
int cells (i.e., CD3
int cells of extrathymic origin) remained, especially in the liver. There were two subsets, NK1.1
+ and NK1.1
-, among the IL-2Rβ
+ CD3
int cells. However, the NK1.1
+ subset (i.e., NK1.1
+ T cells) was much more radioresistant, and the majority of CD3
int cells belonged to this subset in irradiated mice. The expansion of lymphocytes from injected BM cells did not occur in the irradiated B6 mice. However, such expansion did take place in irradiated B6-
lpr/lpr mice injected with both BM cells of B6-
lpr/lpr and B6 origin. As a result, the mice subjected to BM cells survived. Irradiated B6 mice were treated
in vivo with anti-NK1.1mAb or anti-asialoGM
1 antibody to eliminate NK cells alone or both NK cells and NK1.1
+ T cells. When irradiated B6 mice were pretreated with anti-NK1.1mAb, the mice could survive. These results suggest that intact NK1.1
+ T cells of extrathymic origin may recognize abnormal BM cells with the
lpr gene and inhibit the expansion of lymphocytes, including abnormal double-negative CD4
- 8
- cells, in B6-
lpr/lpr mice. To inhibit the expansion of lymphocytes, mechanisms other than Fas ligand/Fas molecules on extrathymic T cells may be responsible.
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