McCoy K L, Page M S, Merkel B J, Inman J K, Stutzman R
Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond 23298.
J Immunol. 1993 Dec 15;151(12):6757-68.
The Ag, pigeon cytochrome c, was coupled to human ferric transferrin by a heteroligation technique to target Ag into the endosomal transport pathway via transferrin receptors. The ability of various types of APC that do or do not express transferrin receptors to process exogenous Ag in their endosomes was investigated by the stimulation of Ag-specific CD4+ T cells with the transferrin-Ag conjugate in a serum-free assay. When two B lymphoma cells were the source of APC, the conjugate was significantly more potent than native Ag in activating the T cells, agreeing with our previous finding using a third B lymphoma cell. The conjugate and Ag were similarly presented by splenic B cells that lack transferrin receptors to the T cells. However, both a macrophage hybridoma and a MHC class II-L cell transfectant hardly elicited a T cell response to the conjugate, although a response to native Ag was readily observed. These findings could not be attributed to an absence of transferrin receptors or receptor-mediated internalization of the conjugate, nor to differential expression of MHC class II molecules or li chain by the APC. The poor presentation of the conjugate by the L cell transfectants was associated with diminished catabolism of the conjugate, however, the macrophage hybridoma rapidly degraded the conjugate, similar to the B lymphoma cell. Peritoneal macrophages, which lack transferrin receptors, and the macrophage hybridoma induced a response to the conjugate only at concentrations that allowed internalization by fluid phase pinocytosis. The lower potency of the conjugate compared with native Ag with non-B-presenting cells suggest that these cell types process the conjugate by a different mechanism than used by B cells. Differences in the mechanism of Ag processing used by APC of distinct cell lineages may possibly influence immune responsiveness.
通过异源连接技术将抗原（鸽细胞色素c）与人铁传递蛋白偶联，以使抗原通过转铁蛋白受体进入内体转运途径。在无血清试验中，用转铁蛋白-抗原偶联物刺激抗原特异性CD4 + T细胞，研究了表达或不表达转铁蛋白受体的各种类型抗原呈递细胞（APC）在其内体中处理外源性抗原的能力。当两种B淋巴瘤细胞作为APC来源时，与天然抗原相比，该偶联物在激活T细胞方面明显更有效，这与我们之前使用第三种B淋巴瘤细胞的发现一致。缺乏转铁蛋白受体的脾B细胞将偶联物和抗原以相似的方式呈递给T细胞。然而，尽管对天然抗原有明显反应，但巨噬细胞杂交瘤和MHC II类-L细胞转染体几乎不能引发对该偶联物的T细胞反应。这些发现不能归因于转铁蛋白受体的缺失或偶联物的受体介导内化，也不能归因于APC的MHC II类分子或Ii链的差异表达。L细胞转染体对偶联物的呈递较差与偶联物分解代谢减少有关，然而，巨噬细胞杂交瘤与B淋巴瘤细胞一样迅速降解偶联物。缺乏转铁蛋白受体的腹腔巨噬细胞和巨噬细胞杂交瘤仅在允许通过液相胞饮作用内化的浓度下才诱导对偶联物的反应。与非B呈递细胞相比，偶联物的效力低于天然抗原，这表明这些细胞类型处理偶联物的机制与B细胞不同。不同细胞谱系的APC处理抗原的机制差异可能会影响免疫反应性。
