Immune system Flashcards
What class of cells make up the immune system?
The Haematopoetic cells
What are the two lineages of the haematopoetic cells?
- Myeloid lineage
2. Lymphoid lineage
What % of diseases are dealt with by the innqate immune system?
95%
What soluble is used in:
a) the innate immune system
b) the adaptive immune system
a) Lysozyme and acute phase proteins
b) Antibody
What cells are involved in:
a) the innate immune system
b) the adaptive immune system
a) Phagocytes and natural killer (NK) cells
b) T lymphocytes
How do neutrophils find bacterial cells?
Chemotaxsis:
Attracted to bacterial chemical products such as peptide fMLP
What are the 5 stage of phagocytosis?
- Adherance to the polymorph surface
- Phagocytosis
- Phagosome formation
- Fusion with a lysosomal granule
- Killing and digestion of bacterium
What occurs in lysis?
Neutrophils kill microbes by releasing a reactive oxygen species (also called oxidative burst)
What are the 2 mechanisms of adaptive immunity?
- Humoral response deals with the production of antibodies via B lymphocytes
- Cell mediated response is involved withthe production of T lymphocytes
What are the 3 types of T cells?
- T helper
- T cytotoxic
- T regulator
How do B cells and T cells recognise infected cells?
B cells - antibody on surface
T cells - T cell receptors
What is an antigen?
Any substance that elicits a response from a B or T cell. Can protrude from foreign cells such as bacteria or be secreted into extracellular fluid.
Describe a B cell antigen receptor
Y-shaped molecule containing two heavy chains and two light chains. Transmembrane region anchors the receptor in the B cell plasma membrane. Has a constant region and a variable (V) region where amino acids vary between B cells, this is where the antigen binds.
Describe the antigen receptor of T cells
- Consists of 2 different polypeptide chains, an alpha and beta chain linked via a disulphide bridge
- Also anchored via a transmembrane region
- Also has variable region with an antigen binding site which only binds to fragments of antigens presented on MHC (major histonecompatability complex) molecules on host cells
To which class of MHC molecules do a) helper T cells and b) cytotoxic T cells respond to?
a) Class II
b) Class I
Describe the process of the Class II antigen presentation pathway
- Antigen is engulfed by a macrophage and enzymes cleave it into smaller antigenic peptides
- These attach to class II MHC complex and migrates to cell membrane to be presented
- T cell recognises via CD4+ complex
- Promotes the secretion of cytokines via the antigen presenting cell activating B cells and Cytotoxic T cells (with the same receptors)
Describe the process of the Class I antigen presentation pathway
- Infected cell presents antigenic peptides (transported via Golgi apparatus) on Class I MHC molecules in the membrane
- Recognised by CD8 +ve receptor on cytotoxic T cell
- T cell releases perforin molecules which form pores in the infected cell membrane and granzymes which break down proteins (initiates apoptosis)
What are natural killer cells?
Cells that detect abnormal surface proteins characteristics of virus infected and cancerous cells
What is meant by antigen receptor specificity?
Different antibodies can recognise different epitopes on the same antigen
What is a primary and secondary immune response?
primary - first exposure to the antigen
secondary - repeated exposure to the antigen with a faster response
What is clonal selection?
The process by which the cell with a matching antigen will proliferate forming identical clones which will either become efector cells or long-lived memory cells.
How is the diversity in antibodies generated (using a light chain as an example)
- There are 40 V (variable) segments, 5 J (joining) segments, and 1 constant segment
- Enzyme recombinse links a V and J segment upon differentiation
- RNA splicing removes intervening RNA
What feature of an antibody defines its class?
Heavy chain
What are the 5 antibody classes and what are their roles?
IgM - fast aggloutinator IgD - lymphocyte cell surface IgG - most abundant, crosses placenta IgE - responsible for symptoms of allergy IgA - sero-mucous secretions
What are the 3 steps in an immune response to an allergen?
- IgE bodies produced from initial exposure to allergen bind to receptors on mast cells
- On subsequent exposure IgE recognise and bind to the allergen
- Cross linking of adjascent IgE molecules triggers the release of histamine and other chemicals giving allergy syntoms
Name 5 uses of antibodies
- Diagnostic tests
- Passive immunisation
- Therapeutic treatments
- Identification and isolation of different cell populations
- Purification and functional analysis of proteins
