Weltzien H U, Kempkes B, Studer R, Melchers I, Eichmann K
Max-Planck-Institut for Immunbiologie, Freiburg.
Eur J Immunol. 1988 Mar;18(3):431-7. doi: 10.1002/eji.1830180317.
The specificity of major histocompatibility complex (MHC)-restricted antigen recognition by cytotoxic T cells (CTL) has been clearly correlated to the alpha/beta T cell receptor (TcR) complex on the T cell surface. Occasional changes in the specificity of in vitro cultivated CTL clones, therefore, have been suspected to result from alterations of the genes coding for the TcR alpha and/or beta chain. Here we demonstrate that pronounced variations in the stringency of MHC restriction, previously reported to occur during long-term culture of 2,4,6-trinitrophenyl (TNP)-specific CTL clones, may occur rapidly in a growth-dependent, reversible manner, i.e. without structural TcR variation. Several H-2b TNP-specific CTL clones were shown to possess strong cross-reactivity for H-2k TNP target cells when seeded at low cell numbers, but exhibit reduced or undetectable cross-reaction to H-2k TNP in high-density cultures. Another clone revealed "heteroclitic" properties with significantly stronger cytotoxic activity towards allogeneic (H-2k) than syngeneic (H-2b) TNP-modified target cells. In this case dilute cultures appeared as exclusively allo-MHC restricted, whereas dense cultures were allo/self cross-restricted. In all instances these phenomena were accompanied by cell density-dependent quantitative changes in the expression of Ly-2 and T cell antigen receptor. CTL from dilute cultures had at least 2-fold higher surface concentrations of Ly-2 and CD3 antigens than cells from dense cultures while other surface markers such as Thy-1 or LFA-1 were completely identical. No such effects were observed for CTL clones exhibiting cell density-independent specificity patterns. We conclude from these findings that (a) the stringency of MHC restriction specificity may be significantly affected by the amount of expressed TcR and/or Ly-2 molecules, (b) CTL possess mechanisms to regulate Ly-2 and TcR expression and, hence, their MHC-restricted antigen recognition, and (c) the ability to regulate Ly-2 and TcR expression may be altered during prolonged culture of a CTL clone.
细胞毒性T细胞（CTL）对主要组织相容性复合体（MHC）限制抗原的识别特异性已明确与T细胞表面的α/βT细胞受体（TcR）复合体相关。因此，体外培养的CTL克隆特异性偶尔发生的变化被怀疑是由编码TcRα和/或β链的基因改变所致。在此我们证明，先前报道在2,4,6 -三硝基苯（TNP）特异性CTL克隆的长期培养过程中出现的MHC限制严格性的显著变化，可能以生长依赖、可逆的方式迅速发生，即无需TcR结构改变。几个H - 2b TNP特异性CTL克隆在低细胞数接种时对H - 2k TNP靶细胞具有很强的交叉反应性，但在高密度培养时对H - 2k TNP的交叉反应性降低或无法检测到。另一个克隆表现出“交叉反应性变异”特性，对同种异体（H - 2k）TNP修饰靶细胞的细胞毒性活性明显强于同基因（H - 2b）TNP修饰靶细胞。在这种情况下，稀释培养物似乎完全受同种异体MHC限制，而密集培养物则是同种异体/自身交叉限制。在所有情况下，这些现象都伴随着Ly - 2和T细胞抗原受体表达的细胞密度依赖性定量变化。来自稀释培养物的CTL的Ly - 2和CD3抗原表面浓度比来自密集培养物的细胞至少高2倍，而其他表面标志物如Thy - 1或LFA - 1则完全相同。对于表现出细胞密度非依赖性特异性模式的CTL克隆未观察到此类效应。我们从这些发现中得出结论：（a）MHC限制特异性的严格性可能受到表达的TcR和/或Ly - 2分子数量的显著影响；（b）CTL具有调节Ly - 2和TcR表达的机制，从而调节其MHC限制的抗原识别；（c）在CTL克隆的长期培养过程中，调节Ly - 2和TcR表达的能力可能会改变。
