免疫球蛋白(Ig)是人体受抗原刺激后所产生的具有抗体作用的一类球蛋白。Ig 在体内可和病原体(即抗原)起免疫反应从而阻断病原体对机体的危害。人体的这种免疫能力是物种进化中逐渐发展起来的。最原始的免疫反应出现在环形动物与被囊动物中,即对异物开始有排斥作用。随着淋巴组织的进化,免疫反应也逐渐完善。鸟类是淋巴系统第一个分化为两部份的脊椎动物。其一部份淋巴系统受胸腺控制,所产生的淋巴细胞叫胸腺依赖性淋巴细胞 Immunoglobulins (Ig) are the class of globins that are produced by the human body upon antigen stimulation and have an antibody effect. Ig in the body and pathogens (ie antigens) play an immune response to the pathogen to block the body’s harm. This kind of immunity of the human body is gradually evolved in species evolution. The most primitive immune response appears in the ring animal and tunicate, that is, foreign objects began to have repulsion. As the lymphoid tissue evolves, the immune response also gradually improves. Birds are the first vertebrate to differentiate into two parts of the lymphatic system. A part of the lymphatic system is controlled by the thymus, which produces lymphocytes called thymus-dependent lymphocytes