Complement component 4 is a protein involved in the complement system.
It is cleaved into proteins 4a and 4b.
Classical pathway. (Some labels are in Polish.)
It is responsible for the Chido Rodgers blood group system.
C4d has been identified as a biomarker for systemic lupus erythematosus.
- ^ Chido Rodgers blood group system at BGMUT Blood Group Antigen Gene Mutation Database at NCBI, NIH
- ^ Liu CC, Manzi S, Kao AH, Navratil JS, Ruffing MJ, Ahearn JM (2005). "Reticulocytes bearing C4d as biomarkers of disease activity for systemic lupus erythematosus". Arthritis Rheum. 52 (10): 3087–99. doi:10.1002/art.21305. PMID 16200588.