Question

where in a lymph node do b - cells undergo proliferation, differentiation, and activation?
germinal center
medullary cords
capsule
hilum

Explanation:

B - cells undergo proliferation, differentiation, and activation in the germinal center of a lymph node. The germinal center is a specialized microenvironment within the lymph node's follicle. Here, B - cells that have been activated by antigen - presenting cells (such as follicular dendritic cells) can undergo processes like somatic hypermutation (to improve antibody affinity) and class - switch recombination (to change the antibody class).
The medullary cords mainly contain plasma cells (differentiated B - cells that secrete antibodies) and macrophages. The capsule is the outer covering of the lymph node and does not have a role in B - cell activation and differentiation. The hilum is the region where blood vessels and efferent lymphatic vessels enter and exit the lymph node and is not involved in B - cell functions like proliferation and activation.

Answer:

Germinal center