Germinal centers within lymph nodes are located in which region?

• A. Paracortex
• B. Cortex with lymphoid follicles
• C. Medulla
• D. Subcapsular sinus

Answer: (B)

Germinal centers are the sites of active B-cell proliferation and maturation in response to antigen, and they form within the cortex of a lymph node, specifically inside the lymphoid follicles. The outer cortex contains these B-cell–rich follicles; when they become activated, a secondary follicle with a germinal center develops, appearing as a pale center within the follicle on histology. The paracortex is the T-cell region, the medulla houses plasma cells and medullary cords/sinuses, and the subcapsular sinus is a lymphatic channel just beneath the capsule. Since germinal centers arise from B cells in the cortical follicles during an immune response, the correct location is the cortex with lymphoid follicles.