Molecular structure and expression of anthropic, ovine and murine complement receptor type 2

College of Animal Science & Veterinary Medicine, Shandong Agriculture University, Tai'an, 271018, P R China; Office of Ji Nan Animal Husbandry, Ji'nan 250002, P R China

^* To whom correspondence should be addressed. Email: zxniu{at}sdau.edu.cn.

	Abstract

The complement system covalently attaches C3d, a fragment of C3, to microbial antigens which binds to Complement receptor type 2 (CR2) on B-lymphocytes, leading to a markedly enhanced adaptive immune response to that antigen. CR2, also called CD21, is a receptor that serves as an important interface between the complement system and adaptive immunity. It forms a tight complex with C3d the major complement component. Recent studies have shown that CR2 is also centrally involved in innate immunity, and CR2 has also been demonstrated to play a critical role in the development of humoral immune responses to T-dependent antigens and thus acts as a bridge between the adaptive and innate immune systems. The structure of human, sheep and murine CR2 were characterized by cDNA cloning, protein sequencing and immunoprecipitation. In this review, we wish to relate the molecular structure and expression of human, sheep and murine CR2, and offers insight into future experimental directions.