Rock K L, Rothstein L, Benacerraf B
Division of Lymphocyte Biology, Dana-Farber Cancer Institute, Boston, MA 02115.
Proc Natl Acad Sci U S A. 1992 Oct 1;89(19):8918-22. doi: 10.1073/pnas.89.19.8918.
The association of major histocompatibility complex (MHC) class I molecules on the surface of cells with synthetic antigenic peptides of eight or nine amino acid residues was examined. Peptides were synthesized that correspond to the antigenic sequences from ovalbumin and influenza nucleoprotein believed to be naturally processed and presented by cells with Kb and Db MHC class I molecules, respectively. Consistent with the results of others, these peptides were 10(3)-10(5) times more active in stimulating specific T cells as compared to peptides of longer sequences. When cells are incubated with these peptides at less than 0.01-0.1 microM, the association of the peptides with class I molecules is dependent on (i) the reassociation of free beta 2-microglobulin from the extracellular fluids, (ii) a process that requires cells to be metabolically active, or (iii) stabilization of class I heterodimers by chemical crosslinking. In contrast, when cells are incubated with these peptides at greater than 0.1-1.0 microM, the peptides associate with class I molecules in the absence of exogenous beta 2-microglobulin, energy, or chemical crosslinking. Antigen competition experiments suggest that the class I molecules that bind peptides offered at high concentration become only transiently receptive to binding peptide. The concentration of peptides required for presentation to T cells under these conditions corresponds to those that stabilize Kb molecules on the surface of RMA-S mutant cells in the absence of exogenous beta 2-microglobulin. These results support the concept that the receptivity of class I molecules on cells is determined by the dissociation of beta 2-microglobulin from MHC class I that lacks bound peptides.
研究了细胞表面主要组织相容性复合体（MHC）I类分子与含8或9个氨基酸残基的合成抗原肽之间的关联。合成了与卵清蛋白和流感核蛋白的抗原序列相对应的肽，据信这些抗原序列分别由表达Kb和Db MHC I类分子的细胞进行天然加工和呈递。与其他人的结果一致，与较长序列的肽相比，这些肽在刺激特异性T细胞方面的活性高10³ - 10⁵倍。当细胞与这些肽在低于0.01 - 0.1微摩尔浓度下孵育时，肽与I类分子的结合取决于：（i）细胞外液中游离β2 - 微球蛋白的重新结合；（ii）一个需要细胞具有代谢活性的过程；或（iii）通过化学交联稳定I类异二聚体。相反，当细胞与这些肽在高于0.1 - 1.0微摩尔浓度下孵育时，肽在没有外源性β2 - 微球蛋白、能量或化学交联的情况下与I类分子结合。抗原竞争实验表明，结合高浓度提供的肽的I类分子仅短暂地易于结合肽。在这些条件下呈递给T细胞所需的肽浓度与在没有外源性β2 - 微球蛋白的情况下稳定RMA - S突变细胞表面Kb分子的肽浓度相对应。这些结果支持了这样一种概念，即细胞上I类分子的接受性由缺乏结合肽的MHC I类分子中β2 - 微球蛋白的解离所决定。
