Immunology 1-2 Flashcards
How are bacteria and viruses able to evade the immune system?
Fast replication times so are able to evolve at a much fast rate.
How does strategy 1 work and what receptors are involved?
Recognises molecular patterns using pattern recognition receptors (PRRs) such as PAMPs and DAMPs.
Which strategy is germ-line encoded?
Strategy 1
How does strategy 2 work?
Recognises precise structures with specific antigen receptors on lymphocytes.
Which strategy has a wider diversity of receptors?
Strategy 2 - receptors are formed by random recombination of gene segments creating large diversity.
What makes up the T cell receptors?
Two protein chains (alpha and beta) that are expressed by the T cell.
What are the features of innate immunity?
- Independent of exposure
- Fast
- Limited specificity
- Depends on pre-formed compounds
- Buys time whilst adaptive immunity begins response
What cells are involved in innate immunity?
Neutrophils, basophils and eosinophils (polymorphonuclear leukocytes)
How does innate immunity work?
Destroys invading nucleic acids in the cytoplasm and activates inflammatory pathways. Also stimulates type 1 interferons (anti-viral defence).
What are the features of adaptive immunity?
- Adaptation to exposure
- Slow
- Highly specific
- Can form memory cells
What cells are involved in adaptive immunity?
B cells (humoral) and T cells (cellular)
Where are lymphocytes found in the body?
98% in lymph and remaining are found in the blood.
When do lymphocytes enter the lymph?
When they enter high endothelial venules. T cell receptors on the surface of the T cell recognise chemokines present on the surface of HEVs causing a conformational change, arrest and trans-endothelial migration.
What is the process that produces lymphocytes and where does it take place (adults)?
Lymphopoiesis and in primary lymphoid organs such as the bone marrow and thymus gland.
Where does lymphopoeisis also take place in children?
Spleen, liver and bones.
How does age affect thymic output?
Decreases with age, reducing strength of the immune system.
Where does haematopoesis take place?
Bone marrow in flat bones and ends of long bones.
What is yellow bone marrow associated with?
Fat
What makes up the cutaneous immune system?
Skin and mucosa.
What do epidermal Langerhaans cells do?
Capture antigens on the skin and migrate to a lymphatic vessel where they are presented to T cells.
What do CD markers mean?
Cluster of differentiation. They are an internationally recognised system of nomenclature for cell surface molecules to discriminate between haemotpoietic cells.
What CD marker do all T cells express?
CD3
What do CD4+ cells do?
Involved in T helper cells and regulatory T cells - secrete chemokines. Associated with MHC II.
What do CD8 cells do?
Cytotoxic T cells that are able to lyse infected cells and secrete cytokines. Associated with MHC I.
How do T lymphocytes recognise antigens?
Can only recognised processed antigens that are presented on the surface of an APC using a T helper cell (CD4). Antigen is presented by an MHC molecule.
How do B lymphocytes recognise antigens?
Recognise intact antigens in bodily fluids or on cell surfaces using the BCR. They are then internalised.
What are the three main forms of APCs?
- Dendritic cell
- Activated macrophage
- B lymphocyte
What are the four atypical forms of APCs?
- Mast cell
- Basophil
- Eosinophil
- ILC3
