Immune complexes as immunizing agents to increase the number of monoclonal antibody producing hybrids and to deviate the response to poorly immunogenic epitopes.

The use of immune complexes (IC) in an antibody excess, as immunizing agent, led to a large increase in the mouse polyclonal response to human SIgA. This enhanced response, as compared to SIgA alone, was analysed with mouse polyclonal anti-alpha chain antibodies (Ab). A kinetic study showed an early rise (between days 14 and 21) of the antibody response against the discontinuous epitopes of SIgA while the anti-IgA response increase was delayed. Induction of hybridomas with an IC consisting in SIgA containing an excess of anti-alpha chain Ab, increased 10-fold the number of positive wells. Moreover, two of these MAb were specific for weakly immunogenic epitopes. One recognized only SIgA (anti-C), i.e. the association between the alpha chain and the secretory component (SC), while the other mainly combined to IgA dimers (anti-P). Both these MAb will be useful tools for structural studies and for the dosage of secretory Ab.