FIG. 2.

RIP testing procedure for measuring Abs against a ligand (protein). This method uses fluid-phase binding of sample Abs in a patient's serum with a specific ligand (e.g., radiolabeled EPO [A*]) alone or in a mixture of proteins) (step 1), the subsequent binding of protein A-Sepharose or protein G-Sepharose beads that attach to ligand-Ab complexes (step 2), and the collection of beads by centrifugation (step 3). This assay method can incorporate competitive free (nonradiolabeled) ligand to test the specificity of Abs for individual proteins or peptides. Reproduced from reference 36 with permission.