抗体的糖基化修饰对其功能活性具有重要影响，如岩藻糖的有无会直接影响抗体依赖细胞介导的细胞毒作用（ADCC）和补体依赖的细胞毒作用（CDC），研究证实无岩藻糖化的抗CD20抗体比含有岩藻糖抗体的ADCC提高10倍以上。现有各种糖蛋白表达系统对糖基的修饰过程都是不可控的，因此一般只能通过糖基化位点的突变来研究糖基化"有无"对糖蛋白的影响，而不能详细研究特定结构糖基对糖蛋白的影响。本研究将在前期研究基础上，优化酵母糖基化修饰通路，获得各种具有哺乳动物细胞糖基化修饰能力的新型酵母系统。利用抗CD20或抗Her抗体为模型蛋白，在细胞水平、动物水平检测具有不同糖基化（甘露糖型、杂合型、复杂型糖基）修饰的抗体活性，如ADCC和CDC，建立基于糖基工程酵母的抗体高效表达、规模化发酵和产品制备技术，研究并发现不同的N-糖基结构对抗体蛋白活性的影响，为研制高ADCC或CDC活性的新型抗体提供技术与理论基础。

N-glycosylation is crucial for antibodies’ property. It has been shown that the fucosylation of glycans on human IgG1 affects ADCC (antibody-dependent cellular cytotoxicity) and CDC (complement dependent cytotoxicity) efficacy. For instance, afucosylated glycans can significantly increase IgG1 binding to FcγRIII and enhance ADCC efficacy over 10-fold. However, N-glycosylation modifications on glycoproteins are uncontrolled to date. The glycan profiles of recombinant proteins produced in mammalian cells and yeast are predominantly heterogeneous. Therefore, the relationships between certain glycans and protein functions cannot be clarified by means of current expression systems. The use of methylotrophic yeast system for foreign protein expression is increasing dramatically. Yeasts are capable of performing many human posttranslational modification reactions, including N-linked glycosylation. However, glycoproteins produced in wild type yeast contain potentially immunogenic high-mannose type N-glycans, limiting the use of yeast expression systems for glycoprotein. This study will be performed to optimize and the recreation of the sequential nature of mammalian cell glycosylation in the ER and Golgi. (ii) The monoclonal antibodies (anti-Her2 mAb or anti-CD20 mAb) were used as examples to study glycoprotein production in glycoengineered Pichia pastoris. In this study, we will measure the levels of recombinant yeast derived antibodies protein in heterotetramer folding, physical stability and binding affinity. The combination of glycoengineered Pichia pastoris expression system with established quality control methods maybe provide an alternative production platform for therapeutic monoclonal antibodies with higher ADCC and CDC.