A sandwich enzyme-linked immunosorbent assay for detection of calreticulin in human serum

Calreticulin (CRT) is a 46 kDa Ca(2+) binding chaperone protein that is mainly located in the endoplasmic reticulum luminal and has various biological functions. It is important to establish a specific and sensitive CRT enzyme-linked immunosorbent assay (ELISA) for the study of CRT functions. Therefore, we prepared a polyclonal antibody (PAb) in rabbits immunized with a recombinant CRT protein. Based on the PAb and our previously prepared monoclonal antibody (MAb), a highly specific and sensitive ELISA was developed. In the present study, we describe a sandwich ELISA for the determination of CRT protein in human serum. It was found that soluble CRT (sCRT) concentration in serum samples from 49 lung cancer patients was significantly higher than that from 53 healthy individuals (p=0.004). This result demonstrates that sCRT concentration in sera of lung cancer patients is higher than that in sera of healthy individuals. In conclusion, the prepared CRT antibodies and developed ELISA is a potential tool for CRT research and offers an alternative, simple, rapid technique for detecting CRT, especially in large ongoing and future clinical studies.