A Key Step in the Development of B Cells Is

Multiple Choice

A key step in the development of B cells is the expression of the RAG-1 and RAG-2 recombinase proteins. The up-regulation of RAG-1 and RAG-2 in early pro-B cells is induced by:

A) The cytokine IL-7, which is made by bone marrow stromal cells
B) The chemokine CXCL12, which is made by bone marrow stromal cells
C) The B cell-specific transcription factors E2A and EBF
D) Signaling through the Igα subunit of the B-cell receptor complex
E) Signaling through the FLT3 receptor tyrosine kinase binding to membrane-bound FLT3