Jensen P E
Department of Pathology, Emory University School of Medicine, Atlanta, GA 30322.
J Immunol. 1989 Jul 15;143(2):420-5.
Th cells recognize a processed form of Ag in association with class II histocompatibility molecules expressed on the surface of APC. The physical nature of the cell surface association of physiologically processed Ag was investigated by using membranes isolated from Ag-pulsed APC. Such membranes were sufficient to directly activate class II-restricted T cell hybridomas without further Ag processing. T cell-stimulating activity remained after treatment of membranes in harsh conditions, including pH 4.0, pH 9.0, high salt, and chaotropic solvents. Activity was lost after exposure to pH 2.0 or protease. The capacity of pH 2.0 (but not protease) treated membranes to present artificially processed, peptide Ag to T cells suggests that exposure to pH 2.0 results in the selective dissociation of processed Ag from membranes. Similar results were obtained in parallel experiments with peptide-pulsed membranes. No qualitative differences were found between physiologically processed Ag and peptide Ag with respect to their remarkably stable association with the APC plasma membrane.
辅助性T细胞识别与抗原呈递细胞（APC）表面表达的II类组织相容性分子相关的经加工的抗原形式。通过使用从经抗原脉冲处理的APC分离的膜，研究了生理加工抗原在细胞表面结合的物理性质。这种膜足以直接激活II类限制性T细胞杂交瘤，而无需进一步的抗原加工。在包括pH 4.0、pH 9.0、高盐和离液剂等苛刻条件下处理膜后，T细胞刺激活性仍然存在。暴露于pH 2.0或蛋白酶后活性丧失。经pH 2.0（而非蛋白酶）处理的膜将人工加工的肽抗原呈递给T细胞的能力表明，暴露于pH 2.0会导致加工后的抗原从膜上选择性解离。在肽脉冲膜的平行实验中也获得了类似结果。在生理加工抗原和肽抗原与APC质膜的显著稳定结合方面，未发现定性差异。
