研究B-1a與B-2細胞免疫調節的機轉

Abstract

研究背景： 一群有功能性的B細胞，稱為調節性B細胞，被證明可以維持免疫系統的平衡。它們有能力分泌介白素-10 (interleukin-10, IL-10) 並且表現CD5和CD1d。另一群B細胞，B-1a細胞擁有調節性B細胞的特色，且經過刺激後分泌介白素-10的能力會增加。然而，傳統的B-2細胞在刺激後只能分泌少量介白素-10。根據這兩種B細胞亞群的特色，我們推測B-1a細胞會在免疫反應中扮演調節的角色。因此，我們想要研究B-2細胞和B-1a細胞的調節作用的機轉。 實驗方法： 在共同培養或分隔培養的系統中，我們將分離出的B-2細胞或B-1a細胞和以塗層形式的anti-CD3及anti-CD28單株抗體刺激的CD4+ T細胞培養在一起。經過3天培養，T細胞被分離出來且其增生能力可用[3H]-thymidine incorporation程度及CFSE染色來決定。在抑制過程中是否需要介白素-10的作用是使用中和介白素-10的單株抗體、阻斷介白素-10的單株抗體或介白素-10基因剔除鼠而證明。此外，T細胞和B細胞的特性由FACS分析而細胞激素的分泌由ELISA偵測。 實驗結果： 是B-1a細胞而非B-2細胞藉由介白素-10且不需要細胞之間的接觸有調節作用進而抑制T細胞的增生；然而，從野生型或介白素-10基因剔除鼠分離的B-1a和B-2細胞都可以誘導產生調節性T細胞。經過再刺激，T of B-2細胞產生較多的介白素-2 (interleukin-2, IL-2) 及介白素-10而T of B-1a細胞會分泌較多的干擾素-γ (interferon-γ, IFN-γ) 及介白素-17 (interleukin-17, IL-17)。 結論： 本篇研究結果證明B-1a細胞會藉由分泌介白素-10而執行調節功能且B-2及B-1a細胞都可以藉由誘導調節性T細胞的產生而調控免疫反應。因此，未來更需要進一步研究B-2及B-1a細胞在調控免疫疾病上的應用。 關鍵字： B-1細胞、B-2細胞、調節性B細胞、介白素-10、調節性T細胞、免疫調節

Background: A functional B cell subset, regulatory B cells, has recently been shown to contribute to maintain the balance of the immune system. They are IL-10 competent and express CD5 as well as CD1d. Another B cells subset, B-1a cells, has the features of regulatory B cells and the basal levels of IL-10 increase in response to stimulation. However, conventional B-2 cells secrete only small amount of IL-10 with or without stimulation. Based on the different characters of these two B cell populations, we speculated that B-1a cells might play a regulatory role in immune responses. Hence, we aimed to study the regulatory mechanisms compared between B-2 and B-1a cells. Methods: B-2 and B-1a cells were isolated and cultured with CD4+ T cells which stimulated with coating form of anti-CD3 and anti-CD28 in co-culture or transwell system. After 3 days incubation, T cells were purified and the proliferation ability was determined by [3H]-thymidine incorporation and CFSE stain. The requirement of IL-10 during the suppression process was investigated by using IL-10 neutralizing or blocking antibodies as well as IL-10 knockout mice. Moreover, the features of T and B cells were analyzed by FACS and the cytokines production was determined by ELISA. Results: B-1a cells but not B-2 cells had the regulatory function to suppress the proliferation of T cells through IL-10 dependent but cell-cell contact independent pathway; however, both of B-1a and B-2 cells purified from wild type or IL-10 knockout mice were able to induce regulatory T cells from naive CD4+ T cells. T of B-2 cells produced more IL-2 and IL-10 while T of B-1a cells secreted more IFN-γ and IL-17 after restimulation. Conclusions: Our results demonstrated that B-1a cells executed the regulatory function by secretion of IL-10 and both B-2 as well as B-1a cells might modulate immune responses through the induction of regulatory T cells. In the future, B-2 and B-1a cells should be studied more for further application to modulate immunological diseases via distinct strategies. Keywords: B-1 cells, B-2 cells, regulatory B cells, IL-10, regulatory T cells, immunoregulation