The immune system protects the body from foreign invaders like bacteria and viruses. Specialized structures within this system help organize immune responses. Medullary cords are one such component, serving as important sites for immune cell activity.
Structure and Location
Medullary cords are found within lymph nodes, which are small, bean-shaped organs distributed throughout the body. Lymph nodes are enclosed by a fibrous capsule that sends extensions, called trabeculae, inward. Each lymph node is divided into an outer cortex and an inner medulla.
Located in the inner medulla, medullary cords appear as irregular, cord-like masses of lymphoid tissue. These cords are separated by open spaces known as medullary sinuses, which are vessel-like channels that transport lymph.
These cords are densely packed with various immune cells. They contain antibody-secreting plasma cells (specialized B cells), other B cells, macrophages, dendritic cells, and some small lymphocytes. The structural framework of the medullary cords is made of dense, irregular reticular fibers, which provide support for these cells. Blood vessels also traverse through the medullary cords, supplying and draining blood.
Function in Immunity
Medullary cords are important for the adaptive immune response, especially in antibody production. Within these cords, plasma cells (mature B lymphocytes) produce large amounts of antibodies. These antibodies are released into the surrounding medullary sinuses, then enter lymphatic vessels and the bloodstream, where they circulate to neutralize pathogens.
Beyond antibody production, medullary cords also serve as sites for immune surveillance. Macrophages residing within the medullary cords play a role in filtering lymph that flows through the lymph node. These phagocytic cells internalize and degrade foreign particles and pathogens, effectively clearing them from the lymph. Some macrophages also present antigens to other immune cells, contributing to the activation and coordination of a broader immune response.
The interaction among various cell types within the medullary cords facilitates an effective immune response. B cells, having encountered antigens and received signals from helper T cells in other areas of the lymph node, differentiate into plasma cells within the medullary cords. This organized cellular environment ensures that the body can efficiently produce specific antibodies to combat infections and maintain immunological memory.
Involvement in Health and Disease
The proper functioning of medullary cords is important for maintaining overall immune health. When the body encounters an infection, lymphocytes within lymph nodes, including those in the medullary cords, activate and proliferate. This can cause the nodes to enlarge, often a sign that the immune system is actively fighting pathogens.
Changes in the appearance or cellular composition of medullary cords can provide diagnostic clues for health conditions. For instance, in infections, the cords might show an increased number of plasma cells producing antibodies. Conversely, unusual cell types or abnormal proliferation within these cords can indicate more serious conditions, such as lymphomas.
Lymph node biopsies, which examine the medullary cords, are routinely used in diagnosing diseases. Atypical cells or altered tissue architecture in this region can signal cancers like lymphoma or leukemia, or autoimmune conditions. Medullary cords therefore serve as indicators of the body’s response to infection and systemic inflammation.