Monoclonal antibodies from rats immunized with fragment D of human fibrinogen

Fischer rats were immunized with fragment D (Fg-D) of human fibrinogen (Fg) to obtain antibody specific for neoantigens unique to this molecule. Absorption of serum with whole Fg indicated that some of the antibody produced reacted preferentially with Fg-D. Hybridoma cultures were prepared by fusion of immune rat spleen cells with mouse myeloma P3-X63-Ag8. Monoclonal antibodies obtained from these cultures fell into two classes: (a) Those reacting equally well with Fg and Fg-D. (b) Those reacting preferentially but not absolutely wth Fg-D. Antibody from hybridoma 104-14, a member of the first group had an affinity for Fg-D of 1.5 x 109 M-1 while antibodies from 106-59 and 106-71 (group 2) demonstrated much lower affinities of 1.0 x 107 and 4.7 x 106 M-1, respectively. The cross reactivity of antibodies in the second group indicated that they react with protein conformations that are altered during production of Fg-D from Fg