Biased lambda-kappa ratio in CD19^-/- mice and in BM culture. (A) Bone marrow culture cells and splenic B cells from wt and CD19^-/- mice were stained for IgM, kappa, and lambda and analyzed by FACS. Plot analysis for kappa and lambda expression was performed on gated IgM⁺ cells. Shown is a representative dot plot of 3 different experiments. (B) Histogram summarizing the lambda-kappa ratio expressed in BM culture and spleen cells of wt (□) and CD19^-/- mice (▦). Results expressed are mean ± SE of 3 different experiments. (C) The lambda-kappa ratio in serum antibody. Serum samples from 6 wt (□) and 6 CD19^-/- mice (▦) were analyzed by ELISA for levels of IgM/kappa and IgM/lambda or IgG/kappa and IgG/lambda. Antibody concentrations were calculated using as reference IgM or IgG standard curves. Results are expressed as mean ± SE. Asterisk indicates values that are statistically different (P < .05).