• CD46 is a transmembrane protein known as a complement membrane cofactor protein (MCP) and a receptor for the measles virus. It is widely expressed on leukocytes, platelets, epithelial cells, and fibroblasts. Multiple isoforms of CD46 have been reported, with molecular weights ranging from 45 to 75 kD. 
• CD46 binds complement components C3b and C4b and has been reported to play a role in T cell regulation. In addition to the complement components, CD46 has been shown to interact with moesin, c-Src, tetraspanin 4, c-Yes, and integrin β1. CD46 is also recognized as a cellular receptor for the human measles virus and human herpes virus 6, as well as other human pathogens, such as Streptococcus pyogenes. Defects in CD46 have been associated with hemolytic-uremic syndrome.

Gene targeting strategy for B-hCD46 mice. 
The exons 2~9 of mouse Cd46 gene that encode the extracellular domain were replaced by human CD46 exons 2~11 in B-hCD46 mice.

Strain specific CD46 expression analysis in homozygous B-hCD46 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6 mice (+/+) and homozygous B-hCD46 mice (H/H), and analyzed by flow cytometry with species-specific anti-CD46 antibody. hCD46 was exclusively detectable on neutrophils, T cells, monocytes and macrophages from spleen of homozygous B-hCD46 mice, while hCD46 was not detectable in wild-type C57BL/6 mice. 

Strain specific analysis of CD46 mRNA expression in wild-type C57BL/6 mice and B-hCD46 mice by RT-PCR. Lung RNA were isolated from wild-type C57BL/6 mice (+/+) and homozygous B-hCD46 mice (H/H), then cDNA libraries were synthesized by reverse transcription, followed by PCR with mouse or human CD46 primers. Mouse Cd46 mRNA was detectable only in wild-type C57BL/6 mice. Human CD46 mRNA was detectable only in homozygous B-hCD46 mice but not in wild-type mice.