Immunology Flashcards
Give some examples of the body’s exterior immune defences
Name 3 differences between innate and adaptive immunity
What is the hypothesis behind why developed countries have higher rates of allergic disorders (asthma, eczema, rhinitis) ?
The hygiene hypothesis - early and regular exposure to certain bacteria / parasites promotes immune homeostasis
What is autoimmunity?
Caused by the breakdown of what process?
Name three autoimmune diseases and the tissues that are attacked
Autoimmunity - attack against self-proteins or tissues.
Breakdown of tolerance = autoimmunity
Multiple sclerosis - myelin sheath destruction
Crohn’s disease - gut epithelium
Rheumatoid arthritis - lining of the joints
What is hypersensitivity?
Hypersensitivity reactions are classed as type I-IV. What are some examples of a type I hypersensitivity reaction?
What type of immunoglobulin are involve in type I?
Hypersensitivity - over-reaction to benign antigens
Type I - anaphylactic shock, hay fever, asthma, hives, food allergies, eczema, bee stings, drug allergies, animals, latex.
IgE mediated. Histamine is released.
Reactions happen quickly
Most allergies are IgE mediated type I hypersensitivity reactions
More about hypersensitivity reactions in year 2
Which of the following cells are involved in innate immunity and which in adaptive immunity?
B cells T cells Phagocytes Antibodies Complement NK cells Dendritic cells
What are the primary lymphoid organs and their functions?
Lymphoid organs produce lymphocytes.
Bone marrow - B cells.
Thymus gland - T cells. Where T lymphocytes mature. Thymus is located behind the sternum, it is large during childhood and puberty and shrinks in adults.
What are the secondary lymphoid organs and their function?
Spleen, Tonsils, adenoids, appendix, lymph nodes, Peyer’s patches, MALT (mucosa associated lymphoid tissue)
Mature lymphocytes meet pathogens
Summarise the process of phagocytosis. Which cells do this?
Macrophages - ingestion and destruction of particles / microbes
What are the common types of antigen presenting cell?
Dendritic cell
Macrophage
B cell
Monocytes
MHC class II
What is the difference between MHC class I and II
MHC class I molecules present antigens from inside the cell (endogenous pathway) Found on all nucleated cells
MHC class II molecules present antigens from outside the cell (exogenous pathway) Found on antigen presenting cells
What is antigen presentation
Antigen presenting cells eg. Dendritic cells engulf and destroy pathogen, then present antigen to CD4+ T helper cell
By what process and where are immune cells generated?
Immune cells are generated via haematopoiesis in the bone marrow
What cells do lymphoid progenitor cells differentiate into?
B lymphocytes → plasma cells
T lymphocytes
NK cells
What cells to myeloid progenitor cells differentiate into
End products - platelets, red blood cells, monocytes, granulocytes (neutrophils, basophils, eosinophils)
What does a megakaryocyte produce?
Platelets
Megakaryocyte - Large cell. Big lobulated nucleus. Derived from myeloid stem cell. Produces platelets.
What are reticulocytes?
In what clinical scenario would reticulocytes be high
Reticulocytes are immature red blood cells
Higher proportion of reticulocytes to mature blood cells means bone marrow is rapidly creating blood cells - reticulocytes are high in acute blood loss, or haemolysis where blood cells are being broken down
What is the function of macrophages?
What cell are they derived from
Derived from monocytes
Macrophages are large cells with a single nucleus that ingest pathogens.
Monocytes circulate in the blood, then migrate to tissues where they differentiate into macrophages.
Macrophages:
- In most tissues
- first line of defence
- recognise PAMPs (pathogen associate molecular patterns)
- destroy pathogens using phagocytosis
- secrete cytokines that initiate the inflammatory response
1 Function and 2 characteristics of neutrophils
Neutrophils
- circulate in the blood stream
- migrate to areas of inflammation due to signals (eg IL-8) from macrophages
- destroy pathogens by phagocytosis
Characteristics
- multi-lobed nucleus
- smallest granulocyte
- first white blood cell on the scene
- major constituent of pus
- most abundant white blood cell type
- cytoplasm contains a lot of granules including lysozyme, collagenase and other enzymes
1 function and 2 characteristics of eosinophils
Function
- kills parasites (useful when pathogens are too large to undergo phagocytosis). Wait in tissues until activated by cytokines or respond to invading pathogen.
Characteristics
- red coloured cytoplasm under microscope (eosinophil = eosin loving. Eosin is a pink dye)
- bi-lobed nucleus
- Granules toxic to parasites that are released during degranulation such as ‘major basic protein’ that digests parasites
- circulate in the blood
- also capable of phagocytosis, to lesser extent than neutrophils and macrophages
How are mast cells and basophils
- Similar?
- Different?
These cells have similar functions and were once thought to be the same cell
Both
- contain cytoplasmic granules that contain cytokines
- release histamine and play a role in allergic response eg increases blood vessel permeability
- both contain heparin
Mast cells
- fixed in place in the tissues
- round nucleus
Basophils
- circulate in the blood
- also play a role in parasite destruction like eosinophils
- lobed nucleus
B lymphocytes mature where?
What do they have on their surface?
What two types of cell does it differentiate into? And what are their functions
Mature in the Bone marrow. B = bone.
Have antibodies (immunoglobulins) on the surface - specific to a single antigen/pathogen
Once activated by the antigen it differentiates into either plasma cells or memory B cells
Plasma cells make antibodies
Memory B cells await future infections
T lymphycytes - where do they mature?
What do they have on their surface? What are the two groups?
T lymphocytes leave the bone marrow as ‘pro-thymocytes’ and travel to the thymus gland where they mature into T cells.
Mature in the thymus
Have T-cell receptors on their surface, specific to a single antigen. Two groups - CD4 receptors displayed by CD4 cells, CD8 receptors displayed by CD8 cells.
Note - FAS pathway causes apoptosis
Natural killer cells - how are they different to T cells?
Recognise infected or abnormal cells without needing MHC receptors.
NK cells are different to T cells because they can detect cells that aren’t displaying MHC, allowing for a faster immune reaction. They were named ‘natural killers’ because they don’t need activation to kill cells that are missing the ‘self’ markers of MHC I. This is important because T cells cannot detect cells missing MHC I markers.
If the MHC I is absent, or foreign like in an organ transplant, the natural killer cell will kill the target cell.
Kill cells by releasing cytotoxic granules, induce cell death by apoptosis.
Also secretes interferon-Gamma that further activates macrophages and increases inflammatory response.
