ANATOMY

Detailed explanation-1: -The memory B cells are activated by the variant pathogen to differentiate into long-lived plasma cells or to re-enter the geminal centres (GCs) to replenish the memory B cell pool.

Detailed explanation-2: -Memory B cells are generated in response to T-dependent antigens, during the GC reaction, in parallel to plasma cells (Fig. 2-5). At their exit of GCs, memory B cells acquire migration properties towards extrafollicular areas of the spleen and nodes.

Detailed explanation-3: -Follicular helper T Cells (Tfh). There, they induce the formation of germinal centers, the transformation of B Cells into plasma cells, the production of antibodies with different isotypes, and the production of memory B Cells (35).

Detailed explanation-4: -B cell activation is initiated by the binding of antigen to the B cell receptor (BCR) that triggers a number of signaling cascades that ultimately lead to B cell activation.