欧美国产日韩在线免费观看-欧美日韩成人激情一区二区-欧美久久综合一区二区-亚洲av寂寞少妇久久

Complement component 4 （C4）, in humans, is a protein involved in the intricate complement system, originating from the human leukocyte antigen （HLA） system. It serves a number of critical functions in immunity, tolerance, and autoimmunity with the other numerous components. Furthermore, it is a crucial factor in connecting the recognition pathways of the overall system instigated by antibody-antigen （Ab-Ag） complexes to the other effector proteins of the innate immune response.C4d is a degradation product of complement activator. If C4d is high in the tumor of patients, its survival period will be reduced; Complement fragment C4d can be used as a biomarker for early diagnosis and prognosis prediction of lung cancer patients.