Peripheral B cell selection on the basis of BCR: Identification and characterization.

다국어 초록 (Multilingual Abstract)

B cells are bone marrow-derived lymphocytes that exit to the spleen as immature cells and complete their maturation in the peripheral immune system. The B cell receptor (BCR) repertoire is significantly shaped by selection during B cell maturation. Negative selection is essentially complete by the time immature B cells exit the bone marrow, but has not been clear whether positive selection significantly shapes the BCR repertoire. In this thesis, we first identify a selection event that occurs at the immature to mature B cell developmental step in the periphery of the mouse. The characteristics of this selection event are most consistent with positive selection. We also note that this selection event occurs in transgenic mouse strains that bear different BCR repertoires. We then characterize this selection event and show that it is dependent upon secreted immunoglobulin (Ig) but is unaffected in mice lacking nonpathogenic gut flora. In all, we describe a newly identified B cell selection event that takes place during a developmental step where selection on the basis of BCR was unknown, and we further develop fundamental characteristics of this selection process.