5 - Adaptive Immune Response Flashcards
What do naive t cells need to become activated and produce an immune response?
Antigen Presenting Cell
Where are antigen presenting cells found in the body?
- MALT
- Lymphoid organs (nodes and spleen)
- Blood circulation (plasmacytoid and myeloid DC’S)
How do antigen-presenting cells capture pathogens?
- Macropinocytosis (soluble molecules like toxins)
- Phagocytosis
What PRR’s recognise gram positive bacteria?
TLR2 - Peptidoglycan, LAM
TLR1 - LPS bacteria
e.g Staph aureus and step pneumoniae
What PRR’s recognise gram negative bacteria?
TLR4 - LPS
TLR5 - flagellin
e.g e.coli and N.meningitidis
What are mycobacteria recognised by on PRR?
TLR4
How do APC’s recognise viruses as they invade the cell so won’t reach a PRR?
PRR on the inside of the cell, e.g TLR3, TLR8 (norovirus), TLR9 (adenovirus)
What are different types of dendritic cells and where are they located?
What is the difference between IgG and IgM?
IgM is the first antibody to be produced when an infection occurs for the first time. IgG confers immunity.
What are the two classes of MHC’s? (Major Histocompatability Complex)
MHC Class I
- HLA-A,B or C
- On all nucleated cells
MHC Class II
- HLA-DR, DQ and DP
- Expressed on macrophages, B cells and dendritic cells
What are the two main features of MHC’s?
- Codominant expression from mother and father to increase number of MHC molecules
- Polymorphic genes to increas the number of antigens presented
Why may people be more susceptible to a particular infection than others?
Everyone has the ability to present but the way they present is different. The thing that is presented will determine how effective the immune response is
What are the two functions of antigen presenting cells?
- Processing of pathogen (e.g endo/exogenous)
- Presentation of microbial peptides
What is the endogenous pathway?
- Processing of intracellular microbes e.g virus
What is the exogenous pathway of processing microbes?
- Extracellular microbes e.g bacteria
What is the structure of MHC class I and II?
What are the two different immunities activated by APC’s and why do they activate different immunities?
Humoral Immunity - Extracellular microbes, MHC class II so get antibodies, complement and phagocytosis
Cell-Dependent Immunity - Intracellular microbes, MHC Class I so cytotoxic T-cells, antibodies and macrophages
What is the importance of everyone having a different set of MHC’s?
Human race not wiped out by a single disease
Why may a patient be HIV positive but still have a high CD4 count?
They may be a LTNP/elite controller. The MHC’s the patient has are ones that the virus needs to replicate so doesn’t destroy them
What clinical issues can the different MHC sets in two different people cause?
- Organ transplant rejection: make sure donor matches MHC of patient
- GvH disease: bone marrow transplant
- Autoimmune disease: e.g HLA-B27 in 90% ankylosing spondylitis patients
Where does adenovirus infect and what does it cause?
Epithelial cells and causes respiratory disease and conjuctivitis
What is the process of destruction if a bacteria gets into the blood stream?
- Macrophages (plasmacytoid and myeloid DC’s)
- Spleen clears
What bacteria would you normally find in the peritoneal cavity?
NONE!! if it gets in it can cause peritonitis
Only contains antibodies, leukocytes, water and electrolytes
What does a perforated bowel look like on x-ray?
Space below the diaphragm and maybe some inflammation as commensals from bowel have leaked out
What does pneumonia look like on a chest x-ray and how can you tell it is not in the pleural cavity?
Area of high density in the lungs. Not in cavity as would’ve fallen to bottom as standing up would have caused gravity to act on it and it would have a meniscus
Where are Class I and Class II MHC found respectively?
- Class I molecules are found on all nucleated cells
- Class II molecules are found on dendritic cells, macrophages & B cells (APC’s)
What is the main function of MHC molecules?
- MHC class I: present peptides from intracellular microbes and are recognised by CD8+ T cells
- MHC class II: present peptides from extracellular microbes and are recognised by CD4+ T cells
Where are B and T cells found in the lymph node?
How do T lymphocytes recognise antigens?
- TCR receptor
- CD3 complex (activates both helper and cytotoxic)
- Accessory molecules (CD4 or CD8)
What are the three mechanisms needed to activate a T-lymphocyte?
- Costimulation of TCR and CD28
1. Antigen recognition
2. Activation
3. Cytokine
Explain the activation of the right T helper cells (TH) response.
Illustrate T cell response to intracellular microbes
How do cytotoxic T-lymphocytes kill cells?
- Perforin
- Granzymes through pores to stimulate apoptosis
Explain T cell response to extracellular microbes
See diagram page 8 lecture 14!!
B cells, eosinophils, mast cells, neutrophils
Briefly explain the mechanisms involved in cell mediated immunity and humoral immunity.
How do B-lymphocytes recognise antigens?
- BCR antibody
- Can recognise lots of molecules not just MHC processed ones, e.g lipids, proteins, nucleic acids
How are B lymphocytes activated?
What happens once b-cells are activated?
- Antibody production: IgG, IgA, IgE
- Affinity maturation in antibody response on repeated exposure
- Memory b-cells
What are the different cytokines needed to be produced to produce different types of antibodies in the b-cells
What are the different functions of each class of antibody?
Describe the characteristics of the antibody response in terms of primary and secondary?
What is DiGeorge syndrome?
Immune deficiency of T and B cell function due to impaired thymic development
If someone has a defiency of CD40L on their T-cells, what will be the issue?
They will not be able to acquire immunity to a disease because they cannot switch from IgM to other antibodies.
No isotype switching
Summarise the process of immunity when a bacteria enters a host for the first time
Summarise the process of immunity when a virus enters a host for the first time
