Lecture 2 - Cells & Tissues of the Immune System I Flashcards
What is a major difference between the lymphatic system and the circulatory system?
Lymphatic is an open circuit, unlike the circulatory system
Where do most infections occur? Why is this important?
In the tissue
The tissue fluid is drained into lymphatics, so that the immune system can respond accordingly
Describe lymph circulation
- Tissue fluid drains into lymphatic capillaries
- Travels through lymphatics
- Passes through at least one lymph node
- Draining into subclavian veins
Where are T cells produced?
In the bone marrow, but they develop in the thymus
Which cell is very important for representing what is happening in the periphery in lymph nodes?
Dendritic cells
Describe the structure of a lymph node
- Capsule
- Cortex
- Medulla
- Follicles w/ Germinal centres : B cells
- Paracortex : T cells
- Afferent & efferent lymphatics
Where are B cells found in lymph nodes & white pulp?
Follicle, Germinal centre
Which organs receive lymph?
Lymph nodes
NOT spleen
Which fluids does the spleen receive?
Blood
Describe the structure of the spleen
Trabecular artery & vein
Red pulp: Erythrocytes
White pulp: • PALS: peri-arteriolar lymphatic sheath : T cells • Germinal centre: B cells • B cell corona • Marginal zone • Perifollicular zone
Describe in general the role of the white pulp
Basically like a lymph node; immune response
What is the role of the spleen?
Collects up old, dying red blood cells
What is the rationale for the naming of eosinophils, basophils and neutrophils?
What is the collective name for these cells?
Eosinophils: stain with eosin
Basophils: stain with a basic dye
Neutrophils: don’t stain
These are the granulocytes
What is the general function of the granulocytes?
Phagocytosis
Describe how neutrophils can kill bacteria
- Phagocytosis
- Degranulation
- NETs
Where are neutrophils normally found?
In the blood
They are rarely found in healthy tissue
Where are eosinophils found?
Majority found in the tissues (opposite of neutrophils)
Describe the function of eosinophils
Releases toxic granules that kill parasites Two types of granule: 1. Microbicidal: • Radicals • Toxic proteins
- Immunomodulatory
• Leukotrienes
• Protaglandins
• Cytokines
What are the two types of granules released by eosinophils?
- Microbicial
* Immunomodulatory
What is the function of basophils?
Where are they found?
Granule release:
• Release of histamine from cytoplasmic granules (similar to Mast cells)
• Cytokines
- Role in parasitic infection & allergy (similar to eosinophils)
- Have IgER (similar to Mast cells)
- Role in T cell development
Location
• Recruited out of the blood to the site of infection (similar to neutrophils)
• Are also found in tissue
What is the difference between macrophages and monocytes?
Monocytes: in the blood
Macrophages: in the tissues
What are some features of Mast cells?
- Contain granules; release of histamine (also cytokines)
- Release in response to Fc receptor cross linking
• Have FcER; binds IgE
Where are DCs normally found?
In tissues
What is very important about DCs?
They are innate cells, but they activate the adaptive immune system
What is the function of NKs?
Be specific!
Kill cells through toxic granule release that are missing ‘self’ components on surface
Contents of granule:
• Perforin
• Granzymes
What is the differentiation between NKs and CTLs?
NKs do not have T cell receptors, which which they can recognise specific cells
NKs only kills cells that are recognised as generically expressing non-self components
How many amino acids in an epitope?
8
What are the functions of antibodies?
- Neutralisation
- Opsonisation
- Complement activation
- Cell mediated immunity (ADCC)
What are the important organs of the immune system?
- Bone marrow
- Thymus
- Spleen
- Lymph nodes
- Tonsils
Where is the thymus?
In the chest at the base of the neck
Sitting in from of the thyroid cartilage of the larynx
What are the two progenitor cells in the bone marrow, and what do they give rise to respectively?
Myeloid progenitor: innate cells + erythrocytes
Lymphoid progenitor: adaptive cells (+ NKs)
What are the stem cells in the bone marrow?
Haematopoetic stem cells
Describe phagocytosis
- Pseudopods extend out around the bacterium
- Phagosome forms
- Lysosome fuses with the phagosome
- Degredation of phagolysosome contents
Describe the most important role of neutrophils
Phagocytosis of invaders in infected tissue
How do eosinophils kill invaders?
Release of toxic granules
What is in the immunomodulatory granules release by eosinophils?
• Histamine
Where are the following cells found: • Mast cells • Basophils • Eosinophils • Neutrophils
MS: Connective tissue
Basophils: tissue & blood
Eosinophils: tissue
Neutrophils: in circulation
What is the effect of histamine?
- Increased vascular permeability
* Vasodilation
Where do B cells develop?
They are produced and develop in the bone marrow
Which cell type releases histamine?
Which cell type releases it most potently?
- Mast cells (most potent releaser)
- Basophils
NB Eosinophils release immunomodulatory granules containing leukotrienes & prostaglandins etc.
Which cell type are basophils quite similar to?
Mast cells
