Germinal centre and marginal zone B cells expand quickly in a second Plasmodium chabaudi malaria infection producing mature plasma cells

SUMMARY Antibodies and B cells are critical in the protective immune response to the blood stage of the malaria parasite, Plasmodium chabaudi. However, little is known about the development of memory B cells and their differentiation into plasma cells during infection or after re‐infection. Here we have shown that B cells with phenotypic characteristics of memory cells (CD19+IgD− CD38+, IgG1+) are generated in a primary Plasmodium chabaudi chabaudi infection of mice. In addition, we observed that germinal centre cells (CD19+, GL7+, MHCIIhi) and Marginal Zone B cells (CD19+CD23−IgD−) show faster expansion on re‐infection than in the primary, though other subsets do not. Interestingly, though both IgM− and IgM+ memory cells are produced, IgM+ memory cells do not expand on second infection. The second infection quickly produced mature bone marrow plasma cells (intracellular Ighi, CD138hi, CD9+, B220−), compared to primary infection; which generates a very large population of immature splenic plasma cells (B220+). This analysis suggests that a memory B cell population is generated after a single infection of malaria, which on re‐infection responds quickly producing germinal centres and generating long‐lived plasma cells making the second encounter with parasite more efficient.