Expression of RAG1 by activated human B cells can be enhanced by treatment with extracellular p17. (A) Activation strategy. B cells were negatively selected from fresh human PBMCs and analyzed for purity (99% were CD19+) and expression of CXCR1 and CXCR2 before culture. After 5 d of culture with CD40L and IL-4, B cells were activated, as shown by up-regulation of CD86. (B) Real-time qPCR for Rag1 and Rag2 expression in two representative donors. After 5 d of activation, B cells were cultured for 24 h with medium alone or p17. The fold change of p17 treated vs. untreated cells is shown. (C) Western blot analysis for RAG1 protein expression. After 5 d of activation, B cells were cultured for 24 h with medium alone, IL-8, or p17. p17 induced RAG1 expression in B cells from three of seven donors; one donor is shown.