The multi-functionality of a given antibody, even monoclonal antibody has recently been shown; this raises the possibility that the specificity of an antiserum be due to a population phenomena; i.e., the specificity would be the net result of the affinity of the various antibodies to the same hapten or antigenic determinant. We have shown in many reports, that prolonged and persistent immunization eventually leads to the exhaustion of the response, and this response ceases upon discontinuation of the antigen stimulation. We have therefore postulated the existence of an immunological equilibrium or antigen-dependent immunologic homeostasis, which can be set at different levels and this explains the formation or lack of formation of autoantibodies. This is why we considered it interesting to study the kinetics of the anti-TNP antibody response triggered by persistent and long-lasting immunization of rabbits with TNP-LPS; it was also interesting to study the antibody response to LPS (the latter being a component of the conjugate) and the antibody response to the TNP-cross-reacting DNP and MNP haptens. A group consisting of 6 big albino rabbits was persistently immunized with TNP-LPS (200 micrograms) 3 times per week for 14 weeks and, thereafter, with 2 mg 3 times per week for 26 weeks. Serum anti-TNP and anti-LPS antibodies were titrated respectively with the TNP-Srbc and LPS-Srbc conjugates. Anti-TNP antibodies were titrated before and after absorption of serum with the TNP-EH, DNP-EH and MNP-EH conjugates.(ABSTRACT TRUNCATED AT 250 WORDS)