Intro to Immunity Flashcards
Name the main phagocytes involved in phagocytosis
Although most cells are capable, neutrophils, macrophages, dendritic
cells excel in phagocytosis
These cells can contain, kill and process microorganisms for antigen presentation which is vital in innate immunity as this initiates adaptive immunity
What occurs at lymph nodes?
Lymph enters via afferent lymphatic vessels which filters through multiple layers of antigen presenting cells (APCs), T and B cells
Lymph exits via the efferent lymphatic vessel
Where are immune cells found normally in the body?
Immune cells are normally distributed throughout the body
How does the immune system detect pathogens?
Immune system detects ‘danger’through a series of pathogen associated molecular patterns (PAMPs) or Damage associated molecular pattern
(DAMPs) molecules
Work with both positive and negative signals derived from tissues
What are antigens?
Usually proteins or carbohydrates attached / secreted by microbes and infected cells
Where in the lymphatic system are lymph nodes found?
At regular intervals along the lymph vessels, there are lymph nodes
What are antibodies?
Glycoproteins formed by B cells and plasma cells that bind specifically with high affinity ‘non-self’ antigens
What is the benefit of lymph nodes to the immune system?
Dense concentration of immune cells provides the ideal environment for immune responses. Nodes are common sites for interactions of infections and immune systems
What are the functions of the innate immune system?
- Prevention, control and elimination of infection
- Removal of damaged cells and initiation of tissue repair
- Activating adaptive immune response
- Influence type of adaptive response that develops
What is phagocytosis?
Process by which cells internalise solid matter including microbial
pathogens
Describe the structure of PAMPs
small molecular motifs consevred within a class of microbes which can include: - glycans - lipopolysaccharides - bacterial flagellin - lipoteichoic acid - peptidoglycan - nucleic acid variants e.g. dsRNA
What biological molecules are involved in innate immunity?
Epithelial barriers
- prevent microbe entry
(e. g. skin, GI tract, respiratory tract)
Mucosal secretions
- flushing action and antimicrobial properties
Cells
- Resident in tissues (e.g. mast cells)
- circulating in body (neutrophils)
Proteins - circulating in blood (e.g. complements)
Cytokines
- locally produced by infected cells (interferons)
What are the main events during inflammation?
- increased blood supply to affected area
- increased permeability to vascalature
- migration of WBCs out of capillaries into affected
tissues
How do antibodies produce an immune response?
They can neutralise targets or recruit other components to kill tragets by Fc mediated effector functions
We have the potential to make antibodies against any foreign targets
Describe DAMPs structure
Molecules released by stressed cells undergoing necrosis
They vary depending on cell type and injured tissue
Some endogenous danger signals are proteins
- (heat shock proteins or cytokines)
Non protein DAMPs include:
- ATP
- heparin
- DNA
What are B cells?
Lymphocytes that become plasma cells when activated which produce antibodies (humoral immunity)
What is inflammation?
Process where immune cells are recruited and concentrated to a site of infection or damage
How does adaptive immunity recognise foreign antigens?
The 2 molecules involved are
- immunoglobulins (ig)
- T-cell antigen receptors (TCRs)
Describe the innate immune system
A constant protection against infection from viruses, bacteria, parasites and foreign particles by keeping them out of our body or limiting their ability to move and spread in the body
What is the lymphoid system?
Immunological cells largely organised into tissues and organs
Part of the circulatory system and important in immune system comprising of a network of lymphatic vessels that carry lymph fluid and cells from tissues back into the blood stream
What happens once PAMPs/DAMPs are recognised?
Following recognition PRRs trigger pro-inflammatory and antimicrobial responses by inducing the release of various cytokines
What is the effect of TCR-antigen binding?
Binding activates T lymphocytes via signal transduction leading to cell
proliferation and activity (e.g. cytokine production)
Describe the role of the primary lymphoid organs
- THYMUS & BONE MARROW
Sites of WBC production
differentiate from stem cells, multiply & are programmed and matured into functional cells
Describe the main features of Immunoglobulins (antibodies)
“Glycoproteins produced by plasma B cells (humoral) which specifically recognise & bind to antigens on pathogens preventing disease & aiding pathogen destruction
There are different (sub)classes of immunoglobulins that vary in structure, features and distribution
What are TCRs?
T cell anitgen recpetors found on T cell surface (cellular immunity)
They recognise processed antigen fragments (peptides) presented by host cells
TCR-antigen binding is weak to antigen-antibody complexes
Name the secondary lymphoid organs
- Waideyer’s lymphoid nodes
- Bronchus-associated lymphoid tissue
- Payer’s patch
- Urogenital lymphoid tissue
What is our potential antibody repetoire?
~10¹⁵
How is the immune system categorised?
- Innate immunity
- Adaptive immunity
- Humoral (B cells & antibodies)
- Cellular (T cells & cytotoxic cells)
What are Fc mediated effector functions?
- Phagocytosis and other killing mechanisms
- Inflammation / cell killing
- Serum 1/2 life and placenta transcytosis
These include WBCs and the activation of the complex cascade
Antibody Fc also binds to neonatal Fc receptors
What are antibodies?
Proteins that specifically bind target antigens on microbes or cells
What is the role of the secondary lymphoid organs and tissues?
Site of WBC-antigen interactions
Allow spread of immune response
These organs are associated with the systemic and mucosal immune compartments
Describe the significance of dendritic cells
Significant in phagocytosis, causing antigen processing & presentation to T lymphocytes. They provide a vital link between innate and adaptive immunity
Widely distributed in lymphoid tissues, mucosal epithelium & body organs
How do T cells recognise antigens?
Via TCRs on APCs - they can;t recognise foreign bodies in their native state. T cells can only recognise processed antigens displayed on cell
surfaces
What is the role of the adaptive immune system?
Responds to infection in days/weeks but it is
- potent & highly specific
- responsive to any potential foreign entity
- has memory
What is the significance of adaptive immunity ?
Has ability to provide a powerful defence against infection if innate immunity
is breached
What is immunology?
The study of the body’s systems for preventing disease
What is the significance of T cells?
These control immune responses and combat microbes intracellularly
Different T cells have different functions distinguished by array of proteins on surface (CD markers)
CD4 - helper T cells
CD8 - cytotoxic T cells
What are the different T cell responses?
“Depending on how the anitgen is presented, different T cells are activated
leading to different responses
CD4 helper T cells - secrete cytokines, activating B and T cells
CD8 cytotoxic cells - kill target cells using cytokines, cytotoxic granules &
caspase cascade
What are the main components of adaptive immunity?
Dendritic cells
- Capture, process & present antigens
T lymphocytes
- control response, aid B cells, macrophages and T
lymphocytes directly kill infected tumour cells
Cytokines
- soluble proteins, secreted mainly by T cells
B lymphocytes
- produce and secrete antibodies
