Lymph follicles ( Folliculi lymphatici ), also called lymph nodes ( Noduli lymphatici ), are spherical colonies of B-lymphocytes in which their differentiation and reproduction takes place. They are part of the lymphatic system .
The primary follicles ( primary nodules ) are found almost exclusively in fetuses and newborns. Microscopically, they show a uniform distribution of small lymphocytes. After contact with the antigen , there is a mitotic multiplication and differentiation of the B lymphocytes, which is accompanied by a local separation of the various stages of development.
After contact with the antigen, the primary follicles transform morphologically and are then referred to as secondary follicles ( secondary nodules ). Secondary follicles are surrounded by a cortex of densely packed T lymphocytes (parafollicular space) that migrate in and out via directly adjacent special venules . In the center they have a less dense zone, which is called the reaction center or the seed center . In the germinal center there are cells that are difficult to distinguish microscopically; this is a basic tissue made up of network-like linked antigen-presenting cells (referred to as follicular dendritic cells ) in which macrophages and B-lymphocytes are stored.
As a fine tissue, a secondary follicle shows itself through so-called star sky macrophages. These are enlarged macrophages within the germinal center. The macrophages are enlarged due to the phagocytosis of apoptotic B-cell precursors and are distinguished by a light ring around them.
As solitary follicles ( Folliculi lymphatici solitarii ) individual in which are submucosa preferred Lymphfollikel designated. When inflammation of the mucus membrane, solitary follicles can increase strongly and pinhead. Together bearing Solitärfollikelformationen is called Folliculi lymphatici aggregati , such as the Peyer's patches of the ileum - mucosa . In the tonsils , the lymph follicles are separated from their surroundings by connective tissue. The B-lymphocyte areas in the secondary lymphatic organs (cortical follicles of the lymph nodes , spleen nodules ) are also lymph follicles.
- Schiebler / Schmidt / Zilles: Anatomie , 7th edition
- W. Böcker, H. Denk, Ph. U Heitz, H. Moch: Pathologie, 4th edition, Munich, 2008, p. 99