FIGURE 1.

Tg λ and κ mice show disparate BCR affinities. A, Generation strategy and B cell phenotype of Tg λ and κ mice. Flow cytometric analysis of donor splenic B cells revealed that Tg mice have an equivalent yet higher frequency of marginal zone (MZ; B220⁺CD23^lowCD21^highIgM^high) compared with follicular (FO; B220⁺CD23^highCD21^intIgM^int) subsets than non-Tg mice. Newly formed (NF; B220⁺CD23⁻CD21⁻IgM^int) immigrants were unchanged. Dot plots shown are gated on the B220⁺ population. B and C, Chromatographically purified V_H17.2.25 Id⁺ Igs from the sera of naive Tg λ and κ mice were standardized and serial dilutions were tested for their ability to bind a high or low hapten ratio (NP₂₅ vs NP₄) by ELISA. D, A competitive ELISA was performed using the purified serum Tg Ig to measure average affinities of λ and κ Abs for NP and NIP as described in Materials and Methods. Hapten inhibition curves are shown that represent the percentage of maximal Ab binding to a constant amount of Ag when serial dilutions of competing soluble NP or NIP monomeric hapten (μM) is present. Measurements of the IC₅₀ values are depicted by the dotted horizontal line (NP, Tg κ = 1.86 × 10⁻³ M, Tg λ = 2.21 × 10⁻⁴ M; NIP, Tg κ = 4.69 × 10⁻⁴ M, Tg λ = 2.07 × 10⁻⁵ M). Results are from three independent experiments.