接種過犬傳染性花柳性腫瘤痊癒犬隻的周邊血液來源單核細胞的免疫特性

Abstract

犬傳染性花柳性腫瘤(Canine transmissible venereal tumor, CTVT)是一個可在犬隻間藉由黏膜接觸而傳播的腫瘤；當CTVT細胞在實驗室被接種至健康犬隻身上後，會呈現一個自然生長期，但隨著時間發展又自行消退，因此這種腫瘤的發展模式就成為研究「腫瘤與宿主間免疫反應」的一種良好的實驗性腫瘤模式。但在過去的研究中我們發現，CTVT細胞無法再被接種至已經接種過CTVT且痊癒的犬隻身上，因此本研究擬藉由比較「未接種過CTVT犬隻」及「接種過CTVT犬隻」的周邊血液單核細胞(Peripheral blood mononuclear cells, PBMCs)，在經過與CTVT腫瘤細胞共同培養後的反應，來探討可能的免疫機制。在本研究中，我們首先將此兩種來源的PBMCs先進行淋巴細胞表現型的偵測，結果顯示無論CD3, CD4, CD8, CD21的表現量都無顯著差異。接著再將兩種犬隻來源的PBMCs分別與P期的CTVT細胞共同培養後，進行PBMCs增生試驗、IFN-γ分泌試驗、細胞毒殺試驗及數種細胞素如發炎前驅(Proinflammatory)細胞素(TNF-α, IL-1β, IL-6, TGF-β)、第一類助手(Th1)細胞素(IL-2, IFN-γ)、第二類助手(Th2)細胞素(IL-4,IL-10)與細胞毒殺(Cytotoxic)蛋白(Granzyme B, Perforin)的mRNA表現量偵測等；結果發現兩種犬隻來源的PBMCs經與CTVT細胞共同培養後，除了IL-1β及IL-6兩種細胞素的基因在未接種過CTVT犬隻中的表現量較高外(p<0.05)，其它細胞素表現量及細胞學試驗，均無顯著差異。目前已知IL-1β與IL-6不僅是炎症反應的前驅分泌細胞素，在腫瘤發展過程中也是導致腫瘤發生的前驅因子，具有促腫瘤細胞增生、存活的功能，甚至可導致腫瘤血管增生及轉移；因此我們推測接種過CTVT犬隻的PBMCs再次遇到CTVT細胞時，可能因無法製造足夠量的IL-1β及IL-6，故不利CTVT的生長，但是後續仍需要更深入的研究來證實。

Canine transmissible venereal tumor (CTVT) is a tumor which can be transmitted naturally through mucosa contact between dogs. After CTVT cells were inoculated to healthy dogs, it will grow rapidly and then regress spontaneously. Therefore, it is a good model to investigate the interactions between tumor and host immune system. Previous studies have shown that CTVT cells can not survive in recovered tumor-inoculated dogs. Thus, the present study was designed to investigate the immunity changes of peripheral blood mononuclear cells (PBMCs) from “uninoculated” or “CTVT inoculated and recovered” canines after cocultured with CTVT cells in vitro to infer the possible mechanisms. The analysis of lymphocyte phenotypes showed that CD3, CD4, CD8, or CD21 expression percentage had no significant difference between these two groups. After cocultured of PBMCs from these two sources with P phase CTVT cells, cell proliferation, IFN-γ secretion, and cell cytotoxicity were examined. The degrees of mRNA expression of proinflammatory cytokines (TNF-α, IL-1β, IL-6, TGF-β), Th1 cytokines (IL-2, IFN-γ), Th2 cytokines (IL-4, IL-10) and cytotoxic proteins (Granzyme B, Perforin) were assayed as well. The results indicated that no significant difference were observed in most criteria tested except that cytokines gene expression of IL-1β and IL-6 in uninoculated canine was higher than in CTVT recovered canines (p <0.05). IL-1β and IL-6 are proinflammatory cytokines which has a strong pro-tumorigenic activity to promote tumor cell proliferation and survival and even can cause tumor angiogenesis and metastasis. It is thus speculated that secondary inoculated CTVT cells can not survive may be due to the insufficient production of IL-1β and IL-6. Further investigation is requied to explore the exact roles of these cytokines in CTVT growth.