Changes

==Principle==

==Principle==

*The general priniciple behind the RIA is the competitive binding of a radiolabelled antigen and unlabelled antigen to a high-affinity antibody.

*The general priniciple behind the RIA is the competitive binding of a radiolabeled antigen and unlabeled antigen to a high-affinity antibody.

*Labelled antigen is mixed with antibody until binding sites are saturated

*Labeled antigen is mixed with antibody until binding sites are saturated

*Samples of unlabelled antigen (unknown concentration) are added in progressively increasing amounts  

*Samples of unlabeled antigen (unknown concentration) are added in progressively increasing amounts  

**The two different antigens compete for the binding sites on the antibody

**The two different antigens compete for the binding sites on the antibody

**As the concentration of unlabelled antibody increases, more labelled antigen will be displaced

**As the concentration of unlabeled antibody increases, more labeled antigen will be displaced

*The decrease in bound-radiolabelled antigen is measured- an indication of the amount of antigen present in sample

*The decrease in bound-radiolabeled antigen is measured - an indication of the amount of antigen present in sample

==Technique==

==Technique==