Foundations of Immunology Flashcards
List the major cells involved in the innate immune system.
Phagocytes, NK cells, Mast cells, eosinophils, basophils
List the major cells involved in the adaptive immune response.
Lymphocytes (B and T cells)
What is the main role of the innate immune system?
First responders (non-specific, no memory, exists from birth)
Where are natural killer cells found?
Blood and spleen
What is the function of NK cells?
Kill tumour cells, virus infected cells, bacteria, parasites and fungi
How do NK cells kill their target?
Bore holes in membrane and release perforin and enzymes causing cell to commit suicide
What are NK cells?
Granular lymphocytes of innate immune system similar tp macrophages.
Describe the steps of phagocytosis and intracellular killing.
- Chemotaxis and adherence of microbe to phagocyte
- Ingestion of microbe by phagocyte
- Formation of phagosome
- Fusion of phagosome and lysosome to form phagolysosome
- Digestion of microbe by enzymes
- Formation of residual body containing ingestible material
- Discharge waste
Define the primary lymphoid organs and describe function.
Thymus and Bone Marrow (where B and T cells originate and receive early training)
Define the secondary lymphoid organs and describe function.
Lymph nodes, spleen, mucosal associated lymph tissue (MALT) in peripheral organs (where ‘recognition phase’ takes place in secondary lymphoid organs)
What are the fundamental properties of the adaptive immune system?
Highly specific, immunological memory, AB production, basis of vaccination.
What is the role of B lymphocytes in immunity?
- Produced in bone marrow and mature into plasma cells.
- Ab production (humoral response)
- Express surface immunoglobulins which are the Ag receptor for B cells.
Where are the variable regions of an antibody?
End of Fab region of light chain. This is where the antigen binds.
What bonds are found in an antibody?
Disulphide bridges.
What region of the antibody is the heavy chain?
Fc region (5 types)
What are the five different classes of antibody?
IgM, IgG, IgA, IgE, IgD
What is the function of IgM?
First antibody, good at fixing complement and opsonisation.
What is the function of IgG?
Good opsoniser
What is the function of IgA?
Protects mucosal surfaces, resistant to stomach acid.
What is the function of IgE?
Defends against parasites and causes allergies.
What is the function of IgD?
No known antibody function.
What are the four main function of antibodies?
- Neutralisation
- Opsonisation
- Compliment activation
- Antibody cell-mediated cytotoxicity
Describe neutralisation.
No interaction between receptor and antibody, blocks pathogen entry and neutralising infectivity, eliminated by phagocytosis.
Describe opsonisation.
Antibodies coat antigens which are recognised by phagocytes with specific Fc region on surface. once bound, they eliminate.
Describe compliment activation.
Membrane attack complex (MAC), makes hole in bacterial cell surface and will lyse.
Describe antibody cell-mediated cytotoxicity.
Antibody dependent, coat target, infected cell displays antigens, antibodies bind and recognised by eosinophils, cause degranulation by cytotoxic cells which create pore and destroy.
What pathway produces MHC I antigens?
Endogenous pathway.
What pathway produces MHC II antigens?
Exogenous pathway
What antigens are presented to helper T cells?
MHC II
What do MHC I antigens present and where are they found?
- Present self and on all nucleated cells.
What antigens present viral induced peptides to CD8+ T cells?
MHC I
What do MHC II Present and where are they found?
Present foreign and are found only on professional antigen presenting cells.
What do MHC I antigens present virally induced peptides to?
CD8+ T cells and trigger cytotoxic response.
What do MHC II antigens present exogenous produced antigen to?
CD4+ T cells and activate macrophages and B cells.
What are T helper cells?
Cannot kill, activate and direct other immune cells, essential in B cell antibody class switching.
What is the function of Th1?
Cellular immune response.
- Makes memory T cells
- Works through IL-2
- Cytotoxic response with perforin
- CD8+ T cells
What is the function of Th2?
Humoral immune response
- Produce antibodies
- Th0 helper cells convert to Th2 and causes B cells to convert to plasma cells
- CD4+ cells
What helper cells are involved in the humoral response?
Th2
What helper cells are involved with the cellular immune response?
Th1
What T cells are Th1 cells associated with?
CD8+ T cells
What T cells are Th2 cells associated with?
CD4+ T cells
What is the function of the compliment system?
Bridges gap between adaptive and innate immune system.
- lysis of microbes by MAC
- promote phagocytosis
- stimulate inflammation
- stimulate activation of B cells and antibody production
What are the 3 activated pathways in the compliment system?
- Classical (need Ag-Ab)
- Alternative (need bacterial Ag)
- Lectin (need sugar molecules on bacteria)
What are the common molecules made in all complement pathways?
C3a and C5b
Normal cells are protected from being attacked by compliment through what proteins?
DAF an CD59
What is the role of cytokines?
Chemical messengers in the immune system to facilitate communication between cells.
What are the three main actions of cytokines?
- Autocrine (on self)
- Paracrine (on nearby cell)
- Endocrine (through circulation to distant cell)
Viral infections would typically cause elevated levels of which blood cell type?
Lymphocytes.
