Polyclonal immune network antibodies were quantitated and characterized in a syngeneic BALB/c murine system. Immunizations of BALB/c antifluorescein mAb 9-40 conjugated to keyhole limpet hemocyanin, produced anti-Id (anti-9-40, 39 to 190 micrograms/ml) as well as anti-fluorescein (anti-Fl, 12 to 109 micrograms/ml). Separately, immunizations of polyclonal anti-9-40, developed significant anti-Fl serum levels in the secondary (2 degrees) response (50 to 270 micrograms/ml), which decreased in the 3 degrees response (50 to 180 micrograms/ml) and thereafter, although levels of 9-40 idiotypically related antibodies increased. Polyclonal 2 degrees anti-anti-9-40 exhibited variant anti-Fl active sites, was antigenically more cross-reactive than polyclonal 2 degrees anti-Fl, but did not exhibit affinity maturation for fluorescein relative to 1 degrees anti-anti-9-40. In addition, the 9-40 idiotype constituted a small (less than 1.0%) percent of the 2 degrees and 3 degrees anti-Fl (ab1) immune response. When viewed within the context of an antigenic system that possesses widely diverse idiotypy, continued introduction of polyclonal anti-Id appears eventually to: 1) induce polyclonal ab3 with quantitative expression of idiotypically related antibodies in preference to ab3 of ancestral (9-40) antigenic specificity, 2) relative to ab1, induce a 100-fold increase in the level of ab3 antibodies that have both ancestral idiotype and ancestral antigen reactivity, and 3) induce polyclonal ab3 antibodies with a measurably wider range of antigenic reactivities than those of polyclonal ab1. These quantitative data may reflect the natural state of an immune network in a diverse antigenic response.