Centroblast

A centroblast generally refers to an activated B cell that is enlarged (12-18 micrometer) and proliferating in the germinal center of a lymphoid follicle. Centroblasts form following exposure to follicular dendritic cell cytokines, such as IL-6, IL-15, 8D6, and BAFF and stimulation from helper T cell interactions between their CD40 ligand and the B cell CD40 induces centroblasts to express activation-induced cytidine deaminase, leading to somatic hypermutation. A centroblast generally refers to an activated B cell that is enlarged (12-18 micrometer) and proliferating in the germinal center of a lymphoid follicle. Centroblasts form following exposure to follicular dendritic cell cytokines, such as IL-6, IL-15, 8D6, and BAFF and stimulation from helper T cell interactions between their CD40 ligand and the B cell CD40 induces centroblasts to express activation-induced cytidine deaminase, leading to somatic hypermutation. Morphologically, centroblasts are large lymphoid cells containing a moderate amount of cytoplasm, round to oval vesicular (i.e. containing small fluid-filled sacs) nuclei, vesicular chromatin, and 2–3 small nucleoli often located adjacent to the nuclear membrane. They are derived from B cells. Immunoblasts are distguished from centroblasts by being B cell-derived lymphoid cells that have moderate-to-abundant basophilic cytoplasm and a prominent, centrally located, trapezoid-shaped single nucleolus which often has fine strands of chromatin attached to the nuclear membrane (‘spider legs’). In some cases, immunoblasts can show some morphologic features of plasma cells. Centroblasts do not express immunoglobulins and are unable to respond to the follicular dendritic cell antigens present in the secondary lymphoid follicles.