犬週邊血液CD5lo淋巴球具有自然殺手細胞之特性

Abstract

自然殺手細胞(natural killer cells, NKC)是先天免疫系統中的重要角色，可在未經刺激的情形下毒殺MHC class I表現不正常之病毒感染及腫瘤細胞。NKC之作用最主要是來自其表面抑制型與活化型接受器之調控。NKC在人、小鼠、大鼠、豬和牛等物種有許多研究與結果，但是在犬方面，仍無相關的報告可以提供NKC之特異性接受器或抗原之資訊。本實驗室先前之實驗發現犬週邊血液淋巴球中CD5陽性之細胞可分為低度表現CD5的細胞 ( CD5lo，CD5 low density )和高度表現CD5的細胞 ( CD5hi，CD5 high density )。由於我們於光學及電子顯微鏡下觀察發現CD5lo細胞在IL-2激化後較CD5hi細胞大，並於細胞質中有較多量的大型顆粒。因此我們進一步研究並證實CD5lo細胞在IL-2激化後對CTAC細胞株（犬NKC之標的細胞）有很強的毒殺能力。除此之外，藉由定量RT-PCR的方法，我們發現CD5lo PBL較CD5hi PBL表現較高量的NKC相關基因包括NKG2D、CD16、CD94、CD160、peforin和granzyme B。在IL-2激化後CD5lo細胞較CD5hi細胞表現較高量的NKC相關基因包括NKp30、NKp44、CD16和CD94。綜合上述結果，我們認為CD5lo細胞族群與犬NKC具有密切的關係。此論文乃第一篇針對犬CD5lo細胞進行詳盡的研究及報告並對未來犬NKC的研究有很大的幫助。

Natural killer cell ( NKC) play an important role in innate immune responses. They kill virus infected cells and tumor cells without previous sensitization that lack or have a modified major histocompatibility class I surface molecule. The function of NK cells is regulated by a balance of activating receptors and inhibitory receptors. NK cells have been well-studied in many species, including humans, mouse, rat, procine and bovine. As for canine species, there is lack of data related to NK cell specific receptors or markers. Previous study of our laboratory had discovered that CD5 positive cells in canine peripheral blood lymphocytes can be divided into two populations, CD5 low density (CD5lo) cells and CD5 high density (CD5hi) cells. The size of CD5lo cells were larger than most of T cells and CD5hi cells, and contained numerous large cytoplasmic granules after IL-2 stimulation examined by light and electron microscopy. For this reason, we further studied and prove that after IL-2 stimulation, the CD5lo cell had strong cytotoxicity for CTAC, the target cell for canine NKC, after IL-2 stimulation. In addition, by Real-time RT-PCR, we found that CD5lo PBL had higher level of mRNAs of NK cell-related receptor than CD5hi PBL including NKG2D, CD16, CD94, CD160, perforin and Granzyme B. After IL-2 stimulation, CD5lo cells had significantly higher NK cell-related receptor mRNAs than CD5hi cells including NKp30, NKp44 , CD16 and CD94. Taken together, we belive that CD5lo subset is strongly associated with canine NKC activities. This is the first report to detaily characterize CD5lo in canine speies. These findings are useful for the study of canine NKC.