Adorini L, Guéry J C, Fuchs S, Ortiz-Navarrete V, Hämmerling G J, Momburg F
Preclinical Research, Sandoz Pharma Ltd., Basel, Switzerland.
J Immunol. 1993 Oct 1;151(7):3576-86.
To study the processing and presentation of endogenously synthesized Ag to class II MHC-restricted T cells, hen egg lysozyme (HEL), either tagged with a peptide that confers retention in the endoplasmic reticulum (HEL.KDEL), or in the secretory form (HELs), was stably expressed in LK-35.2 B hybridoma cells. Presentation of HEL peptides bound to class II molecules was assessed by activation of specific T cell hybridomas recognizing seven different epitopes derived from exogenous HEL. The presentation of endogenously synthesized HEL was not caused by reuptake of secreted of shed Ag. All the HEL epitopes examined were efficiently presented after processing of endogenous HEL by HELs-transfected LK-35.2 cells. Processing of HEL tagged with KDEL, however, gave rise to presentation of only six of the seven HEL epitopes. The epitope included in the HEL sequence 112-124 was not presented by HEL.KDEL-transfected B cells. In addition, two of the four T cell hybridomas recognizing HEL 116-129 together with I-Ak molecules were not activated by HEL.KDEL, and three other epitopes were presented with lower efficiency as compared with HELs. Thus, endogenously synthesized HEL in secretory form gives rise to a set of class II-binding epitopes indistinguishable from exogenous HEL, whereas endoplasmic reticulum-retained HEL generates a similar but not identical set of epitopes. The endosomal protease inhibitor leupeptin prevented presentation of the epitope 108-116, but not 46-61, both by HELs and HEL.KDEL transfected cells, indicating a requirement for endosomal processing in both cases. In addition, the presentation of peptides derived from endogenously synthesized, either secretory or endoplasmic reticulum-retained HEL, could be inhibited by lysosomotropic amines, further indicating that the intracellular route of class II molecules presenting peptides derived from endogenous Ag intersects the acidic endosomal compartment.
为研究内源性合成抗原向Ⅱ类主要组织相容性复合体（MHC）限制的T细胞的加工和呈递过程，将带有在内质网中滞留的肽标签的鸡蛋清溶菌酶（HEL）（HEL.KDEL）或分泌形式的鸡蛋清溶菌酶（HELs）在LK - 35.2 B杂交瘤细胞中稳定表达。通过激活识别源自外源性HEL的七个不同表位的特异性T细胞杂交瘤来评估与Ⅱ类分子结合的HEL肽的呈递情况。内源性合成的HEL的呈递并非由分泌或脱落抗原的再摄取引起。在HELs转染的LK - 35.2细胞加工内源性HEL后，所有检测的HEL表位均能有效呈递。然而，用KDEL标记的HEL的加工仅产生七个HEL表位中的六个的呈递。HEL序列112 - 124中包含的表位未被HEL.KDEL转染的B细胞呈递。此外，四个识别HEL 116 - 129与I - Ak分子的T细胞杂交瘤中的两个未被HEL.KDEL激活，与HELs相比，其他三个表位的呈递效率较低。因此，分泌形式的内源性合成HEL产生一组与外源性HEL无法区分的Ⅱ类结合表位，而内质网滞留的HEL产生一组相似但不完全相同的表位。内体蛋白酶抑制剂亮肽素可阻止HELs和HEL.KDEL转染细胞呈递表位108 - 116，但不能阻止呈递表位46 - 61，这表明两种情况下均需要内体加工。此外，溶酶体促透胺可抑制源自内源性合成的分泌型或内质网滞留型HEL的肽的呈递，进一步表明Ⅱ类分子呈递源自内源性抗原的肽的细胞内途径与酸性内体区室相交。
