Lymphoid Structures Flashcards
What are 1º immune system organs?
Bone marrow (immune cell production, B cell maturation)
Thymus (T cell maturation)
What are 2º immune system organs?
Spleen
Lymph nodes
Tonsils
Peyer patches
They allow immune cells to interact with Ag
What are functions of lymph nodes?
- Nonspecific filtration of macrophages
- Storage of B and T cells
- Immune response activation
What encapsulated 2º lymphoid organ has many afferents and only 1 or more efferents?
Lymph node
What is the site of B cell localization and proliferation in lymph node?
Follicle (outer cortex)
What is the difference between 1º and 2º follicles of lymph node?
1º follicles: dense, dormant
2º follicles: pale central GERMINAL center, ACTIVE
Components of lymph node medullary cords?
Closely packed lymphocytes
Plasma cells
Medullary sinuses
Components of medullary sinuses?
Reticular cells
Macrophages
Which part of the lymph node enlarged in bacterial infection?
2º follicles: Germinal center (outer cortex)
Which part of the lymph nodes is enlarged in an extreme cellular response (eg. viral infection) ?
Paracortex (T cell response)
(eg, EBV and other viral infections →
paracortical hyperplasia → lymphadenopathy)
Paracortex of lymph node house which type of cells?
T cells
Which part of the lymph node is not well developed in DiGeorge syndrome?
Paracortex
Where do T and B lymphocytes enter the lymph node from the blood?
HEVs (high endothelial venules)
Where does B cell maturation take place?
Bone marrow
Where does T cell maturation take place?
Thymus
Germinal centers in 2º lymphoid tissues are the result of the proliferation of which cells?
B cells
These are clones of proliferating, Ag-specific cells
What is the 1st signal for the activation of B lymphocytes in 2º lymphoid organs?
Ag binding
and cross-links the idiotype of the Ig
Which mutation occurs during intense proliferative response of the B cell (formation of germinal centers)?
Somatic hypermutation
What type of mutation is somatic hypermutation?
Where does it occur?
Random single point mutation (in Ab idiotype)
Variable domain region
What is the advantage of single point mutations in Ab idiotype?
Increased affinity for the Ag
The process in which clonal selection results in the predominance of clones capable of producing antibodies with ↑affinity for Ag is called ____?
Affinity maturation
How does isotype switching that happens with affinity maturation affect antibody avidity (↑ or ↓) and affinity (↑ or ↓)?
↓ avidity
↑ affinity
Describe the flow of lymph in lymph node
Afferent lymphatic vessels
↓ valve
Sub-capsular sinus (cortex)
↓ Cortical sinus (paracortex)
↓
Medullary sinus
↓ valve
Efferent lymph vessels
What happens in the germinal center of a lymph node?
B cells activate, proliferate, differentiate, and mutate (humoral immunity)
Class (isotype) switching
Somatic hypermutation (↑ affinity to antigens)
Deep cervical lymph node cluster drain which areas?
↑?
Head
Neck
↑
- URTI
- Inf mono
- Strep Pharyng
- Kawasaki’s
- Malignancy head/ neck/ oropharynx
Hilar lymph node cluster drain which areas?
↑?
Lungs
↑ - Infection, inflammation Pulmonary TB (unilateral hilar) Sarcoidosis (bilateral hilar) Lung cancer Granulomatous disease
Mediastinal lymph node cluster drain which areas?
↑?
Trachea
Esophagus
↑ - primary lung cancer, granulomatous disease
Axillary lymph node cluster drain which areas?
↑?
Upper limb
Breast
Skin above umbilicus
↑ - Mastitis, Breast cancer metastasis
Superior mesenteric lymph node cluster drain which areas?
↑?
Lower duodenum
Jejunum
Ileum
Colon up to splenic flexure
↑ - Mesenteric lymphadenitis, Typhoid fever, Ulc. colitis, Celiac disease
Inferior mesenteric lymph node cluster drain which areas?
↑?
Colon from splenic flexure to upper rectum
↑ - Mesenteric lymphadenitis, Typhoid fever, Ulc. colitis, Celiac disease
Internal iliac lymph node cluster drain which areas?
↑?
Lower rectum to anal canal (above pectinate line)
Bladder
Vagina (middle third)
Cervix
Prostate
↑ - STDs
Superficial inguinal lymph node cluster drain which areas?
↑?
Anal canal (below the pectinate line)
Scrotum
Vulva
Skin below umbilicus (except popliteal area)
↑ - STDs, pararectal abscess
Para-aortic lymph node cluster drain which areas?
↑?
Testes
Ovaries
Kidneys
Uterus
↑ - metastases
Popliteal lymph node cluster drain which areas?
↑?
Dorsolateral foot
Posterior calf
↑ - cellulitis
Celiac lymph node cluster drain which area?
↑?
Liver
Stomach
Spleen
Pancreas
Upper duodenum
↑ - Mesenteric lymphadenitis, Typhoid fever, Ulc. colitis, Celiac disease
Trachea & esophagus lymph drain into which lymph node cluster?
Mediastinal
Lower duodenum, jejunum, ileum, colon up to splenic flexure drain into which lymph node cluster?
Superior mesenteric
Anal canal (below the pectinate line), scrotum, vulva, skin below umbilicus (except popliteal area) drain into which lymph node cluster?
Superficial inguinal
Testes, ovaries, kidneys, uterus drain into which lymph node cluster?
Para-aortic
Liver, stomach, spleen, pancreas, upper duodenum drain into which lymph node cluster?
Celiac
Lower rectum to anal canal (above pectinate line), bladder, vagina (middle third), cervix, prostate drain into which lymph node cluster?
Internal Iliac
The colon, from splenic flexure to upper rectum, drains into which lymph node cluster
Inferior mesenteric
Right lymphatic duct drains which areas?
Upper right thoracic cavity (via Rt broncho-mediastinal trunk) above diaphragm
Right arm (via Rt subclavian trunk)
Right side of the head and neck (via Rt jugular trunk)
Thoracic duct drains which areas?
All areas except Rt thoracic cavity, Rt side of head & neck, Rt arm.
Thoracic duct drains into which veins?
Junction of Left subclavian vein & Left internal jugular vein
(at the commencement of the brachiocephalic vein)
Right lymphatic duct drains into which veins?
Junction of the Right internal jugular & Rt subclavian veins
Sinusoids are long, vascular channels with fenestrated barrel hoop basement membrane in which part of the spleen?
Red pulp
What are the components of splenic red pulp?
Sinusoids
Cords
Plasma cells
Which lymphocytes are found in follicles of 2º lymphoid tissues?
B cells
Where are T cells located in the spleen?
White pulp - PALS PeriArteriolar Lymphatic Sheath
central artery enveloped by sheath of T cells
Where are B cells located in the spleen?
White pulp - follicles
Marginal zone - specialized B cells
What are the components of splenic white pulp?
Follicle (B cells)
PALS PeriArteriolar Lymphatic Sheath (T cells)
What is function of splenic marginal zone?
Macrophages (remove encapsulated bacteria)
Specialized B cells
APCs (capture blood-borne Ag for recognition by lymphocytes)
What are the zones of the spleen?
Hematological zone - Red pulp
Immunological zone - White pulp
Ag screening & processing zone - Marginal zone
Splenic PALS PeriArteriolar Lymphatic Sheath contain which lymphocytes?
T cells
High endothelial venules (HEVs) use which lymphocyte surface molecules and their counter-receptors to facilitate lymphocyte entry?
L-selectin
&
Peripheral lymph node addressins (PNAds)
Macrophages in spleen remove which type of organisms?
ENCAPSULATED
- Pseudomonas aeroginosa
- Neisseria meningitides
- Streptococcus pnemoniae
- Klebsiella pneumonia
- Group B streptococci
- E. coli
- H. influenzae B
- Salmonella
- Yersinia pestis
- Bacillus anthracis
- Cryptococcus Neoformans
Splenic dysfunction lead to ↑ susceptibility to which organisms ?
Splenic dysfunction (eg. splenectomy, sickle cell disease):
↓IgM → ↓complement activation → ↓C3b opsonization → ↑ susceptibility to encapsulated organisms
(pneumococcal, Hib, meningococcal)
Important prep for patients undergoing splenectomy?
Vaccination against encapsulated organisms
pneumococcal, Hib, meningococcal
What cell types seen post-splenectomy?
- Howell-Jolly bodies (nuclear remnants, basophilic DNA fragments in RBCs which haven’t expelled the nucleus properly)
- Target cells
- Thrombocytosis (loss of sequestration of platelets and removal)
- Lymphocytosis (loss of sequestration WBCs)
Where do T cells differentiate and mature?
Thymus
Which embryological structure is the thymus derived from?
Third pharyngeal pouch
Thymus EPITHELIUM: third pharyngeal pouch (endoderm)
Thymic LYMPHOCYTES: mesoderm
Lymphocytes are of mesodermal origin or mesenchymal origin?
Mesodermal
What are contents of thymic cortex?
Immature T cells
dense, pink
What are contents of thymic medulla?
Mature T cells
(pale)
Hassall corpuscles
What are Hassall corpuscles?
Thymic bodies in medulla of thymus formed from:
eosinophilic type VI epithelial reticular cells arranged concentrically
(central mass, consisting of one or more granular cells, and capsule formed of epithelioid cells - like rose petals)
Hypoplastic thymus is seen in which conditions?
DiGeorge syndrome
SCID (severe combined immunodeficiency)
What is the common associated disorders with thymomas?
Myasthenia gravis
Superior vena cava syndrome
Pure red cell aplasia
Good syndrome (hypogammaglobulinemia)
Which part of the lymph nodes is enlarged in EBV infection?
Paracortex (T cell response)
paracortical hyperplasia → lymphadenopathy
Oral cavity is drained by which lymph node cluster?
Submandibular
Malignancy of oral cavity can lead to a pathology (increase) in which lymph node cluster?
Submandibular
Supraclavicular lymph nodes drain which area?
↑?
Abdomen and pelvis
(Virchow node)
↑ Malignancy of abdomen, pelvis
Mastitis & breast cancer metastasis affect which lymph node cluster?
Axillary lymph nodes
Hand & forearm are drained into which lymph node cluster?
Epitrochlear
Secondary syphilis can lead to pathology in which lymph nodes?
Epitrochlear
Epitrochlear lymph nodes ca ne enlarged in which pathology?
Secondary syphilis
Periumbilical lymph nodes drain which area?
↑?
Abdomen and pelvis
(Sister Mary Joseph node)
↑ Gastric cancer
What happens if the thoracic duct is ruptured due to a malignancy?
Chylothorax
(thoracic duct damage with chyle leakage from the lymphatic system into the pleural space, usually on the right side. Manifests as pleural effusion)
What is chylothorax?
Thoracic duct damage with chyle leakage from the lymphatic system into the pleural space (tumors/ iatrogenic/ idiopathic) usually on the right side. Manifests as pleural effusion
Gastric cancer may primarily cause the enlargement of which lymph node clusters?
Supraclavicular (Virchow node)
Periumbilical (Sister Mary Joseph node)
APCs capture blood-borne Ag for recognition by lymphocytes in which splenic zone?
Marginal zone
How can the normal thymus in neonates be visualized?
Main feature?
CXR
‘sail-shaped’
By which age does the thymus normally involute?
3 years