Summary
The acquisition of monoclonal antibodies specific for human fibrin has been impaired
by the similarity in chemical composition between fibrinogen and fibrin and the conformational
difference between immobilised and soluble fibrinogen. Five monoclonal antibodies
(mabs) with a known affinity for fibrin have been subjected to screening procedures
which involved the presentation of different forms of both fibrinogen and fibrin to
the test mabs. It was observed by scanning electron microscopy that dried fibrin (denoted
fibrin D), immobilised on the wells of PVC plates was morphologically similar to the
fibrin found in human clots whereas PVC-immobilised fibrin monolayers (fibrin M) and
a homogenised form of fibrin (fibrin FF) presented two very different morphological
appearances. It was shown that lack of cross reactivity of a mab with an antigen (e.g.
fibrinogen) was validly demonstrated only when both mab and antigen were present in
the soluble state. These findings have allowed the generation of a screening procedure
which involves the use of fibrin D on PVC plates in conjunction with whole human plasma
incubated with the test antibody. This screening procedure has been validated using
two mabs, one of which has an exclusive fibrin affinity while the other has a broad
spectrum crossreactivity with both fibrinogen and fibrin. This procedure would ensure
the acquisition of all the five fibrin-specific mabs used in this study while other
less reliable screening procedures might not.
