Chicken anti-protein L for the detection of small amounts of protein L in the presence of IgG

Protein L is a cell surface protein, expressed by Peptostreptoccocus magnus, which binds to the variable light chains of immunoglobulins without interfering with antigen binding. It can be used for purification of mammalian antibodies of all classes in contrast to the Ig-binding proteins protein A and protein G. Detection of protein L leakage into antibody preparations is important, since protein L could interfere in immunological assays and cause adverse reactions in vivo. Here we have developed a sandwich ELISA for detection of protein L in the presence or absence of mouse IgG utilizing specific chicken IgY antibodies. Protein L does not react with chicken IgY light chains, and it is therefore possible to make an antigen-specific assay. The assay can be used to detect protein L at a concentration of 0.3 ng/mL in the presence of IgG.