FIG. 6.

Impaired generation of antigen-specific IgG1-bearing cells in Cd19^Cre/+ Mapk1^flox/flox mice can be countered by overexpression of Bcl-2. Bone marrow cells derived from Cd19^Cre/+ Mapk1^flox/flox and Cd19^Cre/+ Mapk1^+/+ mice were retrovirally infected and transferred intravenously into lethally irradiated wild-type mice as recipients. (A) Frequency of GFP-positive cells. Ten weeks after bone marrow transfer, peripheral blood of reconstituted mice was collected and GFP-positive B220⁺ cells were evaluated by flow cytometry. Histograms represent results from one of four independent experiments. GFP-positive cells: Cd19^Cre/+ Mapk1^+/+-mock, 20.1% ± 2.4%; Cd19^Cre/+ Mapk1^+/+-Bcl-2, 21.4% ± 4.9%; Cd19^Cre/+ Mapk1^flox/flox-mock, 16.7% ± 1.5%; Cd19^Cre/+ Mapk1^flox/flox-Bcl-2, 20.7% ± 5.7%. (B) Ten weeks after bone marrow transfer, mice were immunized with TNP-KLH in alum, and then 7 days later, the numbers of TNP⁺ IgG1⁺ GFP⁺ B220⁺ and TNP⁺ IgM⁺ GFP⁺ B220⁺ cells in a spleen were analyzed as described for Fig. 4. The plots show the averages and standard errors of the means from at least three independent experiments.