Measurement in human blood of fibrinogen/fibrin fragments containing the B beta 15-42 sequence.

This paper describes a radioimmunoassay for the B beta 15-42 peptide derived from human fibrinogen or fibrin. Iodinated B beta 15-42 is bound by specific antiserum and binding can be completely inhibited by excess of the non-iodinated B beta 15-42, B beta 1-42 or B beta 1-118. These peptides cannot be distinguished in this assay. Furthermore, fibrinogen can also completely inhibit binding of iodinated B beta 15-42 peptide. Due to the cross-reaction with fibrinogen, clinical blood samples require a processing step prior to their use in this radioimmunoassay. Ethanol precipitation allows for fibrinogen removal and a near quantitative recovery of both added B beta 15-42 peptide as well as of the endogenous blood peptide(s) containing the B beta 15-42 sequence. The mean level of B beta 15-42 immunoreactive material in normal individuals was found to be 0.41 pmol/ml while that in one group of patients was 20-40 times this value.