Generation of antibody diversity in the immune response of BALB/c mice to influenza virus hemagglutinin. I. Significant variation in repertoire expression between individual mice

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Abstract
The paratypic and idiotypic diversity of the BALB/c antibody response to the hemagglutinin (HA) of the influenza A/PR/8/34 virus (PR8) was investigated using a panel of 125 anti-HA hybridoma antibodies derived from 14 BALB/c mice. The paratypic diversity, as assessed by a fine specificity analysis using 51 related influenza viruses, was extensive: 104 distinct paratopes were observed. In 3 instances, antibodies with indistinguishable paratopes were isolated from 2 individual mice. A minimum estimate of the size of the adult BALB/c anti-HA paratypic repertoire, calculated from these data, is 1500. The generation of this diverse repertoire was studied by screening the anti-HA hybridoma panel for the presence of idiotypes (Id) that are markers for variable (V) region sequences derived from related germ line V genes. Three cross-reactive Id (IdX) that are markers for the V.kappa.21C, V.kappa.21B and V.kappa.21A, D, E or F L chain subgroups were found, respectively, on 16, 1 and 10 anti-HA hybridoma antibodies derived from 7 individual BALB/c mice. Thus, the V.kappa.21 IdX+ hybridomas constitute 22% of the anti-HA hybridoma panel. The V.kappa.21 IdX are also present on 8.6% of .kappa.-bearing Ig in normal BALB/c serum. This suggests that the V.kappa.21 group is used preferentially in the BALB/c anti-HA immune response. The generation of the anti-HA repertoire was further studied using large panels of anti-HA hybridomas derived from 2 individual adult BALB/c mice. Anti-I antisera were raised in rabbits against individual hybridomas from each mouse. One anti-Id serum defined a family of 4 idiotypically and paratypically related, but not identical, antibodies from mouse 36, which represented 31% of the hybridoma antibodies isolated from this mouse. None of the 112 anti-HA hybridoma antibodies derived from 13 other individual mice showed Id cross-reactivity. This Id could not be detected in anti-PR8 antisera from 75 individual BALB/c mice. Another anti-Id serum defined a family of 27 idiotypically related antibodies from mouse 37, which represented 50% of the hybridoma antibodies isolated from this mouse. Only 1 of the 71 hybridoma antibodies isolated from 13 other individuals was Id cross-reactive. Thus, individual adult BALB/c mice express paratypically and idiotypically distinct antibody repertoires to the PR8 HA and somatic mutation evidently plays an important role in the generation of the adult anti-HA repertoire. Mechanisms that could account for differences in repertoire expression among individual mice are discussed.