Lymph Node Pathology Flashcards
What are the primary lymphoid organs?
the bone marrow and the thymus
What are the secondary lymphoid organs?
lymph nodes, spleen and MALT
Describe the morphology of a lymph node?
the lymph node is a small well circumscribed oval surrounded by a fibrous capsule. The hilum of the lymph node has the artery and vein and the efferent lymphatic. The afferent lymphatics enter through the capsule. Inside the lymph node there is an outer cortex and inner medulla.
What is located in the outer cortex of the lymph node?
B cells in follicles and germinal centres
What is located in the paracortex of the lymph node?
T cells
What is located in the medulla of the lymph node?
blood vessels, sinuses and the medullary cords
What are the medullary cords?
lymphatic tissue in the medulla where B cells go for their final differentiation
What cells are located in the sinuses of the lymph nodes?
macrophages and eosinophils
What are high endothelial venules?
the post capillary venules in lymphatic tissue that have plump endothelial cells to allow lymphocytes to enter the lymph node by crossing the high endothelial venules
How can you tell the difference between a follicle and a germinal centre?
in the germinal centre cells are larger and have more cytoplasm and there is a pale area in the centre surrounded by a mantle zone (the naive B cells surrounding the germinal centre)
What happens to B cells once they have matured into plasma cells in the medullary cords?
they can either stay in the medullary cords and release antibodies from there or they can circulate in the blood to go to the tissues
What happens to T cells once they have matured into effector T cells?
they need to go to the site of the infection so will circulate in the blood or lymph
Where are high endothelial venules located?
in the paracortex
What immunological marker is used to stain for B cells in the lymph node?
CD20
What immunological marker is used to stain for T cells in the lymph node?
CD3
What is the role of macrophages in the germinal centre?
to phagocytose the apoptotic B cells
What does the presence of germinal centres in a lymph node indicate?
that there is a humoral immune response occuring - this happens often - even when there is not an overt infection
What are some causes of reactive lymphadenopathy?
localised infection in the area of drainage, systemic infection, non infective systemic disease e.g. rheumatoid arthritis, drugs, other
What are some causes of neoplastic lymphadenopathy?
leukaemic infiltration, lymphoma, metastases
What is the histopathological pattern of a lymph node due to a microbial infection causing acute lymphadenitis?
neutrophil infiltration, oedema, follicular hyperplasia - nodes will be painful due to rapid expansion
Why is chronic lymphadenopathy not painful?
because there is not rapid expansion of the lymph node