Measurement in human blood of fibrinogen/fibrin fragments containing the Bβ 15–42 sequence

Abstract This paper describes a radioimmunoassay for the Bβ 15–42 peptide derived from human fibrinogen or fibrin. Iodinated Bβ 15–42 is bound by specific antiserum and binding can be completely inhibited by excess of the non-iodinated Bβ 15–42, Bβ 1–42 or Bβ 1–118. These peptides cannot be distinguished in this assay. Furthermore, fibrinogen can also completely inhibit binding of iodinated Bβ 15–42 peptide. Due to the cross-reaction with fibrinogen, clinical blood samples require a processing step prior to their use in this radio-immunoassay. Ethanol precipitation allows for fibrinogen removal and a near quantitative recovery of both added Bβ 15–42 peptide as well as of the endogenous blood peptide(s) containing the Bβ 15–42 sequence. The mean level of Bβ 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.