ANTI-METATYPE ANTIBODY STABILIZATION OF FV-4-4-20 VARIABLE DOMAIN DYNAMICS

Anti-metatype (anti-Met) antibodies are immunoglobulins that specifica lly recognize and stabilize antibodies in their liganded or metatypic state, but lack specificity for either the hapten or the unliganded an tibody. Autologous anti-Met antibodies were previously observed in viv o, suggesting that a metatypic autoantibody response could play a phys iological role in the immune network, e.g. controlling the clearance o f immune complexes from circulation. The first elicited anti-Met antib odies were against the fluorescein-liganded high affinity murine anti- fluorescein monoclonal antibody 4-4-20. The fluorescein-hapten system has proved to be an invaluable tool for both the recognition and chara cterization of the metatypic response by utilization of its spectral p roperties. In this investigation, hydrostatic pressure measurements, i n conjunction with fluorescence spectroscopy, were performed on the re combinant Fv derivative (Fv 4-4-20) of the high affinity anti-fluoresc ein monoclonal antibody 4-4-20 complexed to anti-Met antibodies to stu dy the influence of anti-Met antibodies on Fv 4-4-20 intervariable dom ain interactions. Anti-Met antibodies bound to liganded Fv 4-4-20 were observed to cause a change in the fluorescence properties of fluoresc ein that was not observed when anti-Met antibodies were bound to the l iganded parent immunoglobulin. The variation of these spectral propert ies upon addition of anti-Met antibodies was shown to be correlated wi th dissociation of the variable domains in Fv 4-4-20 in response to it s interaction with the anti-Met antibody. The ability to cause variabl e domain dissociation was dependent on whether monoclonal or polyclona l anti-Met antibodies were bound to the metatype. A model was proposed that elucidated the interaction of anti-Met antibodies, polyclonal an d monoclonal, with variable domains of the primary anti-antigen antibo dy.