흰쥐 가슴샘 재생과정에서 CD70의 발현 특성 = Expression of CD70 during Thymus Regeneration in the Rat

국문 초록 (Abstract)

CD70은 TNF superfamily에 속하는 제2형 막당단백질로써 주로 큰포식세포, 활성화된 T 세포 그리고 B 세포에서 발현된다. CD70은 T 및 B 세포와 NK 세포에서 주로 발현되는 TNF receptor superfamily에 속하는 CD27과 결합함으로써 면역반응 동안에 림프구의 증식, 분화, 성숙 그리고 이동을 조절한다.
본 연구에서는 흰쥐에 cyclophosphamide (CY)를 투여하여 가슴샘의 급성 퇴축을 유발시킨 후, 가슴샘 재생과정 동안에 면역조직화학, 이중면역형광조직화학 및 역전사 중합효소 연쇄반응법을 이용하여 CD70의 발현 특성을 관찰하였다. 역전사 중합효소 연쇄반응 분석 결과, 가슴샘속질수지상세포주, DC2.4 세포주 및 RAW264.7 세포주에서 CD70의 발현을 확인하였다. 면역조직화학염색 결과, 정상 및 재생중의 흰쥐 가슴샘에서는 CD70이 큰 포식세포에서 발현되었고, 이들은 주로 가슴샘겉질에 분포하였을 뿐만 아니라 가슴샘 재생과정 동안 CD70 양성반응 세포들의 수와 크기가 현저하게 증가하였다. 또한 재생중의 가슴샘으로부터 분리한 가슴샘세포와 가슴샘 바탕질세포에서 CD70 mRNA 발현이 정상 대조군에 비해 증가하는 것을 확인하였다. 따라서 본 연구의 결과는 가슴샘 재생과정 동안 CD70이 그 수용체인 CD27을 통해 가슴샘 재생에 중요한 역할을 수행할 것이라는 사실을 시사해준다

다국어 초록 (Multilingual Abstract)

The thymus is the central lymphoid organ for development of bone marrow-derived precursor cells into mature T-cells. The thymic stroma provides the specialized microenvironment for the proliferation, differentiation, and maturation of the immature T-cells, thymocytes. The CD27 is a tumor necrosis factor (TNF) receptor family
member whose expression is limited to cells of the lymphoid lineage. CD70, the ligand of CD27, is a TNF related
trans-membrane protein induced upon activation on T and B cells, dendritic cells and macrophages. CD70/CD27
interaction plays a key role in T dependent B cell responses and is responsible for plasma cell differentiation. This study was performed to investigate the expression of CD70 during regeneration following acute involution induced by cyclophosphamide (CY) in the rat thymus using RT-PCR analysis and single and double immunohistochemistry. The results from RT-PCR analysis showed that CD70 is expressed in mouse thymic medullary interdigitating (IDC)-like cells (MDC), DC2.4 and Raw264.7 but not expressed in the mouse thymic epithelial cells (subcapsular/cortex epithelial cells, cortical epithelial cells and medullary epithelial cells). Interestingly, upregulation of CD70 expression was observed in the thymic stromal cells and thymocytes isolated from rat thymus during thymus regeneration. Furthermore, immunohistochemistry demonstrated that CD70 was mainly expressed in the ED1 positive macrophages predominantly in the thymic cortex both in the normal thymus and during thymus regeneration. In line with the data obtained by biochemical analysis, CD70 immunoreactive macrophages is increased both in number and in size during thymus regeneration. Thus, the results of the present study suggest that CD70 expressed on the thymic macrophages could play a role in the development of new T cells to replace T cells damaged by cyclophosphamide treatment during thymus regeneration.

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