A secondary follicle of a lymph node with germinal center (400X)

This image is showing a secondary follicle. The lighter area in the center is called the germinal center with its light and dark zone. In the germinal centre, new B cells (memory B cells) are formed from naive B cells and precursors to plasma cells.

In the light zone of the germinal center (top) we find many follicular dendritic cells but also B lymphocytes, T helper cells and macrophages. In the dark zone (bottom) we mainly find B-lymphoblasts and macrophages. They've been marked on the image, but to be honest, it's hard to tell them apart. There are more mitoses in the dark area compared to the light area. A mantle of unstimulated B cells surrounds the germinal center.