6.5.2 Cells and tissues of the immune system Flashcards
What are the different types of WBCs?
Granulocytes:
Eosinophil.
Basophil.
Neutrophil
Mononuclear cells:
Lymphocytes.
Monocyte
Which 2 cells are involved in the phagocytosis (ingestion) of bacteria?
Neutrophils (granulocytes)
Macrophage (evolves from circulating monocytes) [mononuclear cells]
Which 2 cells are involved in the destruction of parasites?
Eosinophils (found in the circulation).
Basophils (tissue mast cells, found under epithelial surfaces).
What cell is involved in the immunity the viruses?
Lymphocytes (mononuclear cell)
Lymphocytes are supported by what?
Lymphoid tissues
What are the 2 types of lymphoid tissues/organs?
Primary Lymphoid Organs:
Bone marrow, Thymus
Secondary Lymphoid Organs:
Lymph nodes, Spleen, Mucosal associated lymphoid tissues -MALT (e.g. Peyer’s patches)
What is the difference between primary and secondary lymphoid organs?
Primary organs are there for lymphocyte development
Secondary organs are involved in the response to infection
Where are B cells of the lymphocytes developed?
They remain in the bone marrow
Where are T cells of the lymphocytes developed?
They must leave the bone marrow and go to the thymus to be ‘educated’
What is the thymus?
The site of T cell development.
Explain the histology of the thymus:
Has lobes.
Has a darker outer cortex.
Has a lighter inner medulla.
T cells enter via the peripheral capsule and make their way to the medulla until they meet a blood vessel where they can escape
What 2 ‘decisions’ do T cells have to make in the thymus?
1- Each T cell must generate a unique antigen receptor (TCR)
2- Each T cell must decide whether to become a CD4+ or CD8+ cell
What is Thymic lymphoma (cats)?
Neoplasia of thymic lymphocytes.
Associated with FeLV infection.
Clinical signs: anorexia, weight loss, dyspnoea
What is Bursa of Fabricius?
Found in birds.
Referred to as “Cloacal tonsil”.
Is the bird’s primary lymphoid organ for maturation and differentiation of B cells.
What are lymph nodes?
Scattered strategically all around the body.
Function to protect certain areas of the body
Explain the lymph node structure:
Kidney shaped, filters lymph
Lymph enters via afferent lymphatic vessels and leaves via efferent lymphatic vessels
Inner medulla with medullary chords
Arterial vessel (supply)
Venous vessel (drain)
What are the separate T and B cell areas of a lymph node?
B cells migrate to the follicles.
T cells live and work in the surrounding tissue (the paracortex)
What is the function of lymph nodes?
Filters tissue fluid (lymph) and traps foreign organisms/ antigens
environment for recognition of antigen
lymphocyte activation and differentiation
List the 5 superficial lymph nodes that are palpated in a clinical exam.
Mary Poppins Anus Sells Pictures
Mandibular
Prescapular
Axiallary
Sub-inguinal
Popliteal
What is the structure of the spleen?
Red pulp for haematological functions.
White pulp for immunological functions (acts as a filter for blood)
What are the functions of the spleen?
Haematopoietic organ in foetal life
Removal of particulate material from bloodstream:
- foreign organisms
- old RBCs.
Immune responses to blood-borne pathogens.
Store of RBCs and platelets
How is tissue fluid (lymph) produced and returned to the circulation?
Excess fluid produced and drained via lymphatic system to return to circulation.
Lymph nodes located near lymph
What ducts drain what?
Thoracic duct drains body
Tracheal duct drains head
They join to empty into one large venous vessel cranial to the heart to return to plasma
How do antigens enter lymph nodes? (2)
Free antigen swept in afferent lymph and is trapped
Antigen presenting cells eat antigen and then migrate via afferent lymph to LN paracortex
What is the role of the dendritic cells?
- Differentiate from monocytes
- Immature DCs at epithelial surfaces eat antigens
- Migrate via afferent lymphatics to LN to process antigens before presenting to T cells
- Stay in LN paracortex to present to naive T cells
What are high endothelial venules (HEVs)
- Instructs lymphocytes when its time to get off
- HEVS + lymphocyte = cell adhesion molecules so that the lymphocytes can attach and squeeze their way through the HEV area into the lymphoid tissues
Following activation in the lymph node, what happens to the cells?
- Multiplication (thousands of clones)
- Differentiation (into a mature phenotype)
- B cells -> plasma cells (migrate from follicles to medullary cords to start producing antibodies)
- Activated T cells leave LN to search for infection
What is the system, by which lymphocytes travel around various secondary organs?
Immune surveillance:
