2001 Volume 34 Issue 1 Pages 30-35
Liposome immune lysis assay (LILA), which depends on immune lysis of artificial phospholipid vesicles by the activation of complement, is a homogeneous immunoassay method and much better than ELISA in respects of simplicity and rapidity in measurements. Fluorescent agents have been used as markers encapsulated in liposomes, but they need an expensive apparatus for detection. In this work, we measure the concentration of polyclonal and monoclonal antibodies by LILA by use of antigen-bound liposomes encapsulating coenzyme β-NAD+. Conjugated redox reactions involving β-NAD+ can accumulate a colored material and attain a high sensitivity similar to fluorescent agents in detection of released marker. We also analyze the characteristics of immune lysis of liposomes in LILA depending on the equilibrium relationship between antigen and antibody. The marker release depends on the concentration of the antibodies, and the decrease in the concentration of liposomes raises the sensitivity. The marker release is proportional to the concentration of antigen-antibody complex formed on liposomes. Polyclonal antibody can sensitively be detected even at a lower average association constant than monoclonal antibody.