Transformation of LMTK- cells with purified class I genes. V. Antibody-induced structural modification of HLA class I molecules results in potentiation of the fixation of a second monoclonal antibody.

A potentiation phenomenon was observed with HLA-A3 and CW3 transformed murine L cells between anti-HLA class I B10.6 (potentiated) and B10.8 (potentiating) monoclonal antibodies (m.Ab.). Further studies of this phenomenon with these transformed L cells indicated that: 1) no significant specific binding of B10.6 m.Ab. to HLA-A3 and CW3 transformed L cells could be demonstrated by conventional radioimmunoassay or cytofluorometric study in the absence of B10.8 m.Ab.; 2) potentiation of the fixation of B10.6 m.Ab. was induced by other anti-HLA class I m.Ab., which all reacted with the same cluster of antigenic determinants; 3) potentiation reflects an increased specific fixation of B10.6 m.Ab. to HLA class I molecules implicating its combining site; 4) potentiation was mediated by B10.8 Fab fragments. These results indicate that potentiation of the fixation of B10.6 m.Ab. to the HLA-A3 and CW3 molecules expressed by the transformed L cells reflects conformational changes of these molecules after interaction with B10.8 m.Ab.