Lymphoid structures

Question 1

what is a lymph node?

Answer 1

1. a secondary lymphoid organ that has many afferents, 1 or more efferents.
2. Encapsulated, with trabeculae.
3. Functions are nonspecific filtration by macrophages, storage of B and T cells, and immune response activation

Question 2

what are the 3 different structures of lymph node?

Answer 2

1. follicle
2. medulla
3. paracortex

Question 3

which is the site of B-cell localization and proliferation?

Answer 3

follicle

Question 4

what are the 2 sites of follicle?

Answer 4

1. primary follicles: dense and dormant

2. secondary follicles: pale central germinal centers and active

Question 5

what is medulla?

Answer 5

consists of medullary cords which are closely packed lymphocytes and plasma cells + medullary sinus

Question 6

what is the role of medullary sinuses?

Answer 6

communicate with efferent lymphatics and contain reticular cells and macrophages

Question 7

what kind of immune selection takes place in medulla?

Answer 7

negative selection –> T cells expressing TCRs with high affinity for self antigens undergo apoptosis
(positive selection in cortex)

Question 8

which part of the lymph node houses T cells?

Answer 8

paracortex

Question 9

what is paracortex?

Answer 9

regions of cortex btw follicles and medulla

Question 10

what is special about paracortex?

Answer 10

contains high endothelial venules through which T and B cells enter from blood.

Question 11

in pts with DiGeorge syndrome, what structure of lymph node is not well developed?

Answer 11

Paracortex