Intro to immunology Flashcards
What are the major physical barriers to infection?
Saliva
Mucocilliary Escalator
Gastric Acid
Natural Flora
Flushing & urine pH
What cell types are involved in innate immunity?
In blood:
- NK cells
- Basophils
- Eosinophils
- Monocytes
In Tissue
- Mast Cells
- Macrophages
- Dendritic Cells
By what mechanisms does the innate immune system function?
1) Inflammation
2) Recruiting immune cells
3) Complement Activation
4) Opsonisation
5) Phagocytosis
6) NK cytotoxicity
What are cytokines?
Molecules that regulate the nature, duration & intensity of immune responses by binding to specific receptors
E.g. Interleukins, TNF-alpha, chemokines & TGF-beta
Where are cytokines made?
Th cells & Macrophages
Which cytokines are pro and anti-inflammatory?
Pro-inflammatory = TNF-alpha, IL-1, IL-6 & chemokines
Anti-inflammatory = IL-10 & TGF-beta
Describe what happens during inflammation?
Pattern Recognition Receptors (PRR) detect a breach in defence/foreign body and trigger:
- Vasodilation
- Vascular permeability
- Cell Adhesion Molecules
- Chemotaxis
- Sensitivity to Pain
How is complement activated?
C3 is activated first. By any of the 3 pathways, Classical/Lectin/Alternative
What are the functions of complement?
Chemotaxis of phagocytes
Opsonisation
Lysis of micro-organisms
Maintain solubility of Ab/Ag complexes
What is Opsonisation?
Tagging cells for phagocytosis
Done by complement C3b/C4b, antibodies & plasma cells
What do NK cells do in innate immunity?
Perforin-induced Apoptosis
Define an antigen vs antibody?
Antigen is any molecule that induces an immune response. An antibody is a glycoprotein made by b cells that binds antigens
What are the 2 types of adaptive immunity?
Humoral - B cells & Abs
Cell-mediated - T Lymphocytes
How do adaptive immune cells recognise antigens?
B cells/Abs detect BCR directly
T cells detect MHC on antigen presenting cells
Immune Tolerance is a process of ensuring our Lymphocytes are tolerant towards our own tissues. Where does this occur?
Central Tolerance:
T = Thymus
B = Marrow
Peripheral Tolerance:
- 2nd lymphoid organs & circ
What happens during central tolerance?
B cells assessed for self-reacting BCR in the marrow.
T cells undergo +ve (can they recognise foreign antigen?) & -ve (Do they not recognise self-antigens) tolerance testing in the thymus.
Any failures die
How does peripheral tolerance work?
Regulatory T cells destroy self-reactive lymphocytes
What are the major types of T cells?
Cytotoxic (CD8+)
Helper (CD4+)
Regulatory
What do CD8+ T cells do?
Cytotoxic
They induce apoptosis in target cells and release anti-viral/tumour cytokines (IFN-gamma & TNF-alpha)
What do CD4+ T cells do?
Helper:
Activate B cells
Also release cytokines and activate other inflammatory cells e.g. macrophages, mast cells, basophils etc.
Which type of Th cell attacks which type of pathogen?
Th1 targets intracellular pathogens
Th2 & Th17 target extracellular pathogens
Other than peripheral tolerance, what else do regulatory T cells do?
Secrete anti-inflammatory Cytokines (IL-10 & TGF-beta)
Suppress Th & cytotoxic T cells
Which immunoglobulins are monomers, dimers & pentamers?
Monomer - IgG, IgE, IgD
Dimer = IgA
Pentamer = IgM
Which immunoglobulin can cross placenta?
IgG
Which immunoglobulin is involved in parasites and allergies?
IgE
Which antibody activates complement?
IgM
What are the functions of immunoglobulins?
1) Immune complex formation
2) Opsonisation
3) Classical Complement Activation
4) Ab-dependant Cellular Cytotoxicity (ADCC)
What are the major causes of Secondary Immune Deficiency?
Environmental e.g. malnutrition or trauma
Disease e.g. HIV, DM, malignancy or renal failure
Drugs e.g. Glucocorticoids, cyclosporin or Rituximab
