恒定链CLIP两个片段增强体液免疫效果的比较-微生物学专业论文.docxVIP

Abstract Major histocompatibility complex (MHC) is composed of a genes group with same function, shows highly polymorphic and locates in a particular area of the chromosome. Its coding genes express on different cell surface in the process of immune response in antigen presented. The α and β chains of MHC class II molecules with gamma chain polymerization form nine polymers (αβγ)3 in the endoplasmic reticulum。Jones et al. (1978) found that in the different strains of mice, γ chain was different from the polymorphic α and β chans, it showed the nonpolymorphism, so it was called invariant chain (Ii). Ii is an important MHC II chaperone protein molecule and named CD74 in leukocyte differentiation antigens. Ii plays an important role in MHC class II molecule fold correctly, the assembly and its protein expression and antigen-presenting. Ii structure and the mechanism in antigen-presenting were more known. Ii has three domains, cytosolic domain, transmembrane domain and lumenal domain. Its main function is assistance of the MHC class II molecules in exogenous antigen peptide presenting. The lumenal domain contains CLIP (class II-associated invariant chain peptide, 81-104 aa) and trimerization region (TRIM). Research shows that there is binding sites with MHCII (CBS, Class II binding site) in the CLIP. The CBS is divided into two function segments, namely mixed with all polymorphism MHCII promiscuous binding site (PBS, 81-87 aa) and groove binding sites (GBS, 91-99 aa). When the CLIP binds to MHC class II molecules, PBS locates outside of peptides combined groove in MHC class II molecule related with the dissociation of Ii from MHC class II molecules, while GBS locates in the peptide combined groove and interacts with MHC class II molecules. First, Ii structure was analyzed, which could be divided into cytosol domain, transmembrane domain(TM), CLIP and trimerization regions. CLIP could be divided into two segments of PBS and GBS subsection design primers. Previous work