Figure 5.

Summarizing model for sequential IgG switching during consecutive germinal center responses. In a primary response, naive B cells are activated and can undergo IgG subclass switching prior to differentiation into memory B cells. These cells are predominantly CD27⁻ and utilize IGHG3 or IGHG3. Upon secondary encounter, both naïve and pre-existing CD27⁻ memory IgG1⁺ B cells enter the germinal center, where the latter can undergo secondary switching resulting in the CD27⁺ memory B cells which are enriched in IGHG2 transcripts with high levels of SHM.