McCoy K L, Noone M, Inman J K, Stutzman R
Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond 23298.
J Immunol. 1993 Mar 1;150(5):1691-704.
The role of endosomes in exogenous Ag processing was investigated by targeting Ag into the endosomal transport pathway via transferrin receptors. The Ag, pigeon cytochrome c and chicken OVA, were coupled to human ferric transferrin by a heteroligation technique. The conjugates were significantly more efficient than native Ag in stimulating Ag-specific CD4+ T cells, when the APC expressed transferrin receptors. The addition of ferric transferrin eliminated the enhanced response. Paraformaldehyde-fixed APC did not present the conjugates, indicating that the conjugates still required processing to activate T cells. An augmented level of T cell activation was not observed when the APC lacked transferrin receptors or when the conjugate contained the apoenzyme form of transferrin, which does not bind the receptor. The conjugate followed an intracellular pathway similar to that for transferrin, remaining in low density vesicles. Degraded conjugate appeared rapidly in culture supernatants, within 5 min, and peaked by 20 min; under these conditions a T cell response to the conjugate was elicited that was consistent with an early processing compartment. Our results suggest that antigenic peptide fragments can be generated in the early endosomes, without delivery of these Ag to the lysosomes. Thus, various Ag may have differential processing requirements, dictated by their molecular nature, that determine the site of Ag processing.
通过转铁蛋白受体将抗原靶向内体运输途径，研究了内体在外源性抗原加工中的作用。抗原，即鸽细胞色素c和鸡卵清蛋白，通过异源连接技术与人铁转铁蛋白偶联。当抗原呈递细胞（APC）表达转铁蛋白受体时，这些偶联物在刺激抗原特异性CD4+ T细胞方面比天然抗原显著更有效。加入铁转铁蛋白消除了增强的反应。多聚甲醛固定的APC不呈递这些偶联物，表明这些偶联物仍需要加工以激活T细胞。当APC缺乏转铁蛋白受体或偶联物包含不与受体结合的脱铁转铁蛋白的酶蛋白形式时，未观察到T细胞激活水平的增强。偶联物遵循与转铁蛋白相似的细胞内途径，保留在低密度小泡中。降解的偶联物在5分钟内迅速出现在培养上清液中，并在20分钟时达到峰值；在这些条件下引发了对偶联物的T细胞反应，这与早期加工区室一致。我们的结果表明，抗原肽片段可以在早期内体中产生，而无需将这些抗原递送至溶酶体。因此，各种抗原可能因其分子性质而有不同的加工要求，这决定了抗原加工的部位。
