Lymph node. Light micrograph of a section through a lymph node, a filter that keeps the immune system in check, showing lymphoid follicles and connective tissue. The lymphoid follicle walls (dark pink) surround the germinal centre (pale pink), which houses the immune system's B cells (B lymphocytes) and antibodies. Bands of connective tissue (blue) known as trabeculae support the lymph node's interior. A blood vessel (purple ring) is seen within the connective tissue at centre right. Azan stain. Magnification: x30 when printed 10cm wide.