Immunoglobulin assays using nanoparticles

A method of measuring presence and/or amount of a target antibody in a sample, wherein the method comprises:

• a, mixing components of a system and the sample, wherein the system comprises a system for measuring presence and/or amount of a target antibody in sample comprising:
• a nanoparticle adapted to quenching fluorescence emission;
• an Fc binding protein, wherein the Fc binding protein is immobilized or absorbed on the nanoparticle;
• and
• a fluorescing antibody adapted for binding to the Fc binding protein and having a lower binding affinity to the Fc binding protein than the target antibody;
• and
• b. measuring the change in fluorescent intensity observed in the mixture obtained under a as compared to the total fluorescent intensity of the fluorescing antibody before the mixing under a,
• wherein a decrease in fluorescent intensity indicates the presence and/or amount of the target antibody in the sample in an inverse relationship.

A method of measuring presence and/or amount of a target antibody in a sample, wherein the method comprises:

• a. mixing the sample with the components of a system for measuring presence and/or amount of a target antibody in the sample comprising:
• a nanoparticle adapted to quenching fluorescence emission;
• an Fc binding protein, wherein the Fc binding protein is immobilized or absorbed on the nanoparticle;
• and
• a fluorescing antibody adapted for binding to the Fc binding protein and having a lower binding affinity to the Fc binding protein than the target antibody;
• b. measuring the change in fluorescent intensity observed in the mixture obtained under a as compared to the total fluorescent intensity of the system before the mixing under a,
• wherein an increase in fluorescent intensity indicates the presence as or amount of target antibody in the sample.