Id-specific TCR-transgenic SCID mice are protected against subcutaneous challenges with Id⁺ B lymphomas. (A) TCR-transgenic SCID mice and SCID littermates were challenged with the indicated titrated amounts of either A20 cells transfected with the λ2³¹⁵ Ig L chain gene (F9) or A20 cells transfected with the empty pSV2neo vector alone (F55). A palpable tumor of 3 mm was scored as a tumor take. The lowest number of injected F9 cells, 1.25 × 10,³ was not tumorigenic. (B) Id⁺ λ2³¹⁵ Ig in sera of mice injected 12 days earlier with 1.25 × 10⁶ cells. Results were statistically significant (P < .0001), Mann-Whitney test.