Where are follicular dendritic cells (FDCs) mainly located?

Follicular dendritic cells (FDCs) play a crucial role in the immune response, particularly in the activation and differentiation of B cells during the immune response. They are primarily located in the germinal centers of secondary lymphoid tissues, which include lymph nodes and the spleen.

In the germinal centers, FDCs provide a specialized environment for B cells to undergo affinity maturation, which is a process where B cells proliferate and mutate their antibody genes to produce higher affinity antibodies. FDCs express various surface proteins that help trap and retain antigens, allowing B cells to interact with these antigens and their cognate helper T cells effectively. This interaction is essential for promoting class switching and increasing the quality of the antibody response.

The other locations listed, such as the bone marrow and thymus gland, are primarily associated with the development and maturation of hematopoietic cells and T cells, respectively. The spleen's red pulp is mainly associated with filtering the blood and the removal of old or damaged red blood cells, rather than being the primary site for FDCs. Thus, attributing the primary location of follicular dendritic cells to the germinal centers aligns with their critical function in the adaptive immune response.