Radioactive antigen

The non-radioactive antigen (A) and radioactive antigen (A ) are indistinguishable chemically i.e., both of them are identical chemically,... 

Since, both the radioactive and non-radioactive antigens (haptens) are more or less chemically and immunochemically the same, they will eventually compete for the limited number of antibody sites available thus, the amount of radioactivity that ultimately combines with the antibody will be an inverse function of the amount of unlabelled hapten competing for these sites,... 

Antibodies can be combined with enzymes and color reagents or radioactive antigens to produce quantitative testing for drugs. The ELISA or Enzyme-Linked ImmunoSorbant Assay uses antibodies generated against the Ag to be tested for covalently linked to an enzyme which can catalyze a color change reaction such as the NADH to NAD conversion (Xmax at 340 nm). When the Ag-Ab complex is formed the enzyme is activated and the color can be detected. 

Figure 8-33. Precipitation of a standard radioactive antigen in the presence of increasing amounts of non-radioactive competitor. A curve such as this is required for standardization of radioimmunoassays.

Carrier protein solution Biotinylated bovine serum albumin (0.1 mg/ mL) diluted in 2% underivatized bovine serum albumin (in PBS). Radioactive antigen I-labeled (about 2 x 10 cpm/mL) in PBS. 

Methods which evaluate the concentration of the antibody and the radioactive antigen Methods which evaluate the binding constant of the specific binder... 

Figure 13.22 The dextran coated charcoal method for sqt( ratlr bound radioactivity from unbound radioactive antigen.

There are cases where a radioactive antigen is not available. A variant of radio-immunoassay technique, the immunoradlometric assay (IRA), can be adopted in such cases. 

Fixed amount of radioactive antigen A mixed with an unknown amount of unlabeiled antigen A... 

Table 7- Killing of B-precursor cells by specific lethal radioactive antigens (suicide experiment). From Hasten et al. (1971)...

Roelants, G. E., Askonas, B. A. Cell cooperation in antibody induction. The susceptibility of helper cells to specific lethal radioactive antigen. Europ. J. Immunol. 1, 151-157 (1971). 

Unanue, E. R. Antigen binding cells. II. Effect of highly radioactive antigen on the immunologic function of bone marrow cells. J. Immunol. 107, 1663-1665 (1971)-... 

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