Fig. 1.

FtL priming establishes persistent long-term production of serum IgM and IgG anti-FtL at natural antibody levels. IgM and IgG anti-FtL levels measured in sera from WT (BALB/c) and syngenic mutant (Rag1^−/− and AID^−/−) mice primed with FtL or injected with PBS, as indicated. Each dot represents a single mouse; n = 5 per group. Horizontal lines in “quartile box plots” indicate the 25th, median, and 75th percentiles. The dashed line shows background levels (Rag^−/− and AID^−/− sera). Values are expressed as microliter equivalents of a standard serum pool from 5-d FtL primed BALB/c mice (Fig. S1 shows FACS data).