Lymphoid tissues Flashcards
What is the function of non-immune cell swithin body tissue?
- They present antigens to patrolling activated adaptive immune cells
- They also release cytokines to warm off infection
What are some examples of circulating immune cells?
Innate cells (such as neutrophils)
Adaptive cells (such as T and B cells)
What is the function of the lymphatic system?
- It drains tissues and links lymphatic organs
- Helps to remove debris from tissues
Complete the sentence…
The lymphatic system cannot be …(1)… and it runs at a …(2)…, …(3)… speed.
- Closed
- Slow
- Inconsistent
What is lymph made of?
Filtered tissue fluid along with various leukocytes
How does the lymphatic system contribute to immune response?
- It samples the tissues for debris and antigens
- It maximises the chance of specific lymphocyte activation during an infection
What sentinel cells are already present in most body tissues?
Macrophages and dendritic cells
What is the purpose of these sentinel cells?
- Detect pathogens or damage associated proteins
- Act as APCs which then travel to the lymph node
What is the difference between a primary and secondary lymphoid organ?
Primary = where lymphocytes are formed and mature
Secondary = Where lymphocytes are activated
What are the 3 primary lymphoid organs?
- Bone marrow
- Thymus
- Bursa of fabricus
What happens in the bone marrow?
- B cells develop and selection (B cells that produce antibodies against self-cells are filtered out and destroyed)
- Innate immune cells such as neutrophils, monocytes and eosinophils develop here
- T cells originate here (but mature in the thymus)
Where is the thymus situated?
Cranial to the heart
What is the function of the thymus?
It helps to screen out potential auto-reactive T cells before they reach circulation. T cells develop here.
What is the function of the bursa of fabricus?
It is the site of B cell development
Lymph notes are the secondary lymphoid organs, what are the 9 key lymphoids/ lymph nodes?
1) Submandibular
2) Parotid
3) Retropharyngeal
4) Prescapular
5) Axillary
6) Bronchial
7) Mesenteric
8) Superficial inguinal
9) Popliteal
What enters lymph nodes?
- Blood (containing lymphocytes)
- Lymph (containing antigens and APCs)
How do lymphocytes travel through lymph nodes?
- Naive lymphocytes are constantly re-circulating throughout the lymph node
- Lymphocytes enter the lymph node through blood and leave via efferent lymphatic vessels
What is the overall function of lymph nodes?
They act as a highly organised environment evolved for the activation, proliferation and differentiation of lymphocytes.
In which areas of a lymph node are T cells, B cells and APCs found?
- B cells found primary lymphoid follicle
- T cells found in the paracortical area
- APCs found in the medullary cords
What happens inside a lymph node?
1) APCs present antigens to activate T and B cells
2) Activated T cells interact and activate B cells
3) Germinal centres form proliferating B cells which generate high affinity antibodies
What is lymphadenopathy and what could it indicate?
- Enlarged lymph nodes
- Could indicate infection or neoplasia (cancer)
What is the purpose of lymph node aspirations?
It can enable you to look at cell type, cell morphology and pathogen presence and possibly help identify cancer
What do birds and reptiles have instead of lymph nodes?
Lymphoid nodules
What is different about the lymph nodes of a pig?
Pigs have inverted lymph nodes
Where is the spleen located in dogs?
In the left, cranial quadrant of the abdomen near the end of the rib cage
What is the difference between red and white pulp in the spleen?
- Red pulp has haematological functions
- White pulp has immunological functions
What is the function of red pulp?
- Removes particulate matter from the blood stream
- Causes destruction of old RBCs
- Storage of RBCs and platelets
What is the function of white pulp?
Filters microbes, antigens and antigen-antibody complexes out of the blood
How does the spleen help to activate lymphocytes?
- Mature dendritic cells and macrophages migrate from tissues to the spleen via the blood.
- They then reside in the marginal zone and help to activate lymphocytes
What are the 3 different types of MALT? (mucosa associated lymphoid tissues)
GALT = Gut Associated Lymphoid Tissues
NALT = Nasal Associated Lymphoid Tissues
BALT = Bronchus Associated Lymphoid Tissues
Complete the sentence…
There are more …(1)… in MALTs than in the rest of the body
(1) Lymphocytes
What is the main GALT and where is it found?
Peyer’s patches
Found in the ileum and at the ileocaecal junction
What type of cell is found on the surface of Peyer’s patches?
Specialised antigen-sampling M cells
What cells are contained within each of the Peyer’s patches?
- Dendritic cells
- Macrophages
- B cells
- T cells
What is the function of Peyer’s patches?
- Activation of lymphocytes
- Germinal centre formation
- Prevention of inappropriate activation
What would be an example of inappropriate activation?
Food allergies and inflammatory bowel disease
