Brooks A, Hartley S, Kjer-Nielsen L, Perera J, Goodnow C C, Basten A, McCluskey J
Department of Pathology and Immunology, Monash Medical School, Melbourne, Australia.
Proc Natl Acad Sci U S A. 1991 Apr 15;88(8):3290-4. doi: 10.1073/pnas.88.8.3290.
An in vitro model was used to investigate the potential for different structural forms of endogenous antigen to be processed and presented by major histocompatibility complex class II molecules. For this purpose the class II-restricted presentation of an immunodominant epitope of hen egg lysozyme [HEL-(46-61)] was studied in class II-positive B-lymphoma cells (M12.C3) transfected with genes encoding HEL molecules either (i) secreted in high (hi) or low (lo) amounts as soluble antigen [sHEL(hi/lo)], (ii) localized within the endoplasmic reticulum (ER)/salvage compartment (ER-HEL), or (iii) anchored on the cell surface as an integral membrane protein (mHEL). The corresponding sHEL, ER-HEL, and mHEL gene products were expressed as predicted except that HEL determinants accumulated in the culture supernatant as well as on the cell membrane of mHEL-transfected cells. Class II-positive cells endogenously expressing all three forms of HEL antigen constitutively presented the immunodominant HEL-(46-61) determinant with differential efficiency (mHEL, sHEL greater than ERHEL) to a class II-restricted T hybridoma. A second T hybridoma recognized endogenous HEL-(46-61) determinants constitutively presented on sHEL(hi) and mHEL transfectants but not on sHEL(lo) or ERHEL transfectants. The formation of HEL-(46-61)/I-Ak complexes in the ERHEL and sHEL(lo) transfectants was therefore limiting. Mixing experiments with different antigen-presenting cells indicated that the HEL-(46-61) determinant was derived from endogenous antigen rather than by reuptake of shed or secreted HEL determinants. We conclude that MHC class II molecules can present some antigenic determinants derived from endogenous proteins that are sequestered in the ER/salvage compartment as well as distally transported in the form of secretory or membrane antigens.
利用体外模型研究内源性抗原的不同结构形式被主要组织相容性复合体II类分子加工和呈递的可能性。为此，在转染了编码溶菌酶分子基因的II类阳性B淋巴瘤细胞（M12.C3）中研究了鸡卵溶菌酶免疫显性表位[HEL-(46-61)]的II类限制性呈递，这些基因编码的溶菌酶分子分别为：(i) 以高（hi）或低（lo）量分泌的可溶性抗原[sHEL(hi/lo)]；(ii) 定位于内质网（ER）/挽救区室（ER-HEL）；或(iii) 作为整合膜蛋白锚定在细胞表面（mHEL）。相应的sHEL、ER-HEL和mHEL基因产物如预期表达，只是HEL决定簇在培养上清液以及mHEL转染细胞的细胞膜上积累。内源性表达所有三种形式HEL抗原的II类阳性细胞以不同效率（mHEL、sHEL大于ERHEL）组成性地将免疫显性的HEL-(46-61)决定簇呈递给II类限制性T杂交瘤。第二个T杂交瘤识别在sHEL(hi)和mHEL转染细胞上组成性呈递的内源性HEL-(46-61)决定簇，但不识别sHEL(lo)或ERHEL转染细胞上的决定簇。因此，ERHEL和sHEL(lo)转染细胞中HEL-(46-61)/I-Ak复合物的形成受到限制。用不同抗原呈递细胞进行的混合实验表明，HEL-(46-61)决定簇源自内源性抗原，而非通过摄取脱落或分泌的HEL决定簇。我们得出结论，MHC II类分子可以呈递一些源自内源性蛋白质的抗原决定簇，这些蛋白质被隔离在内质网/挽救区室中，也可以以分泌性或膜抗原的形式向远端转运。
