Organs Of The Immune System Flashcards
Central lymphoid tissues
- bone marrow
- thymus
- fetal liver
Peripheral lymphoid tissue
- spleen
- lymph nodes
- MALT
Secondary lymphoid organs
- maturation and activation of lymphocytes
- drain antigen material from tissues and organs
Primary lymphoid tissue
- development of lymphocyte
Internal lymphoid organs
- thymus
- bone marrow
- spleen
- lymph nodes
Surface lymphoid organs
- salivary glands
- respiratory tract
- mammary glands
- intestine
- urogenital system
Sources of lymphocytes
- yolk sac
- bone marrow
- fetal liver
Sites of lymphocyte dev. (Primary organs)
- peyer’s patches
- thymus
- bursa
- bone marrow
Sites where lymphocytes respond to antigens
- peyer’s patches
- bone marrow
- tonsils
- spleen
- lymph nodes
Cell division takes place close to ___
Bone spicules & cytokine-rich ecm
Mature cells are located ____ & released into ____
Closer to sinus lining cells; venous sinus when mature
Thymus
- first lymphoid organ to dev. In fetus
- largest at puberty, then involution occurs
- outer cortex: thymocytes (immature lymphoid cells)
- inner medulla: mature t cells
Hassal’s corpuscles
Function unknown
Thymic epithelial cells
- produce hormones that may have a role in t cell maturation
Hormones of thymus
- trophic hormone
- thymosin-a
- thymopoeitin
- thymulin
- thymus humoral factor
Positive selection
T cells w/ receptors for intermediate affinities
Negative selection
Auto-reactive t cells (recognize self antigens)
Fewer than ___% thymocytes leave thymus
5
Thymic involution
- physiologic
- age related
- decrease of ce
Thymic atrophy
Stressful/pathological conditions (increase in corticosteroids)
Major functions of lymph nodes
- trap antigens
- provide organized area for antigen presentation
- signals to maintain lymphocyte survival
- initiation of adaptive response
- lymphocytes cross into lymphatics by interacting with HEVs
Lymph nodes in pigs
Cortex is inner
Medulla outer
Follicles in lymph node
- primary follicle
- secondary follicle: germinal center
Outer cortex of lymph node cell type
Aggregation of b cells
Paracortex of lymph node
T cells
Para cortex parts
- medullary cord: b cells, plasma cells, macrophages
-medullary sinuses: lymph, macrophages, granulocytes, deliver lymph to efferent lymph vessels
Microorganisms in spleen
- phagocytosed by fixed macrophages and dendritic cells
- encounter b-lymphocytes
- presented to t-lymphocytes
Spleen
- no division of compartments (no cortex or medulla)
- white pulp: b and t lymphocytes, macrophages, antigen presenting cells
- red pulp: reticular fibers and cells, monocytes/macrophages, vascular spaces
Chicken thymus
- 6-7 lobes bilaterally
- lobes by jugular v.
- cortical and medullary regions don’t have clear boundary
- cellular depletion and involution of bursa and thymus happen as bird matures
Immunological differences between birds and mammals
- mammals don’t have bursa of fabricius
- avian many thymus lobes, mammals 2
- avians lack lymph nodes
- avians may have IgD and Ige while mammals have all 5 Igs
- Avians lack IgG subclasses
Thymectomy and bursectomy effect on no. Of circulating lymphocytes
- thymectomy: decrease
- bursectomy: negligible
Graft rejection
- thymectomy: decrease
- bursectomy: not reduced
Cell-mediated cytotoxicity
- thymectomy: decrease
- bursectomy: not reduced
Serum immunoglobulins
- thymectomy: slight decrease
- bursectomy: strong decrease
