マウスリンパ組織におけるレプチンレセプターの発現

Abstract

The mammalian thymus involutes with age. Both the decrease of lymphocyte-accumulated region and the replacement by fat tissue begin at puberty and continue throughout life. In the mouse thymus, though no typical fat cells are found at birth, fat cells appeared at the latest 3 weeks old preceding to the atrophy of cortical and medullary regions. Physiological functions of fat cells proliferated and differentiated in the thymus after birth are unknown. As fat cells appeared in the 3-week-old mouse thymus have shown to express leptin mRNA, we examined whether leptin receptor type b (OBRL) is expressed or not in the thymus and, in comparison, in the secondary lymphoid tissues, spleen, mesenteric lymph node and Peyer' s patch. OBRL mRNA was detected in both thymus and all secondary lymphoid tissues examined by RTPCR method. Furthermore, OBRL mRNA was also detected in the isolated cells with mouse-lymphocyte separation medium from both thymus and spleen free cells washed out in saline from dissected tissues. It is suggested that fat cells differenciated as early as 3 weeks old in the thymus produce leptin and affect other thymus cells, lymphocytes probably, through OBRL. It remains to be clarified whether the leptin-OBRL interaction influences age involution in the thymus.