Introduction into the immune system Flashcards
Define immunology
Is the study of our bodies system for preventing disease
Describe an overview of the immune system
Innate immunity
adaptive = specific and memory cells = cellular t cells and B cells and antibodies
Describe innate immunity in further detail
The innate immune system is your ever-present defence against infection. It is made up of barriers that keep viruses, bacteria, parasites, and other foreign particles out of your body or limit their ability to spread and move throughout the body.
The importance of innate immunity is demonstrated by the fact that you are normally healthy despite the barrage of potential infectious challenges you face every minute.
The innate immune system includes:
1. Epithelial barriers to the environment (eg skin, gastro-intestinal tract, respiratory tract) that prevent microbe entry.
2. Secretions at mucosal surfaces – flushing action and antimicrobial properties.
3. Cells that are resident in tissues (eg mast cells) or circulating in the body (eg neutrophils).
4. Circulating proteins in the blood (eg complement proteins).
5. Cytokines (eg interferons) that are locally produced by infected cells.
6. Non-specific activity.
7. No “memory”, the response is the same to repeated challenge.
How does the immune system know when to work?
- The immune system detects “danger” through a series of pathogen-associated molecular patterns (PAMPs) or damage-associated molecular pattern molecules (DAMPs).
- PAMPs are small molecular motifs conserved within a class of microbes. A vast array include glycans, lipopolysaccharides, bacterial flagellin, lipoteichoic acid, peptidoglycan and nucleic acid variants normally associated with viruses, such as double-stranded RNA.
- DAMPs are molecules released by stressed cells undergoing necrosis. Some are proteins - heat-shock proteins and cytokines. Non-protein DAMPs include ATP, heparin sulfate, and DNA.
- PAMPS and DAMPS are recognized by Pattern Recognition Receptors (PRRs) on immune cells.
What is phagocytosis and describe what cells are good at it, what they do and does it initiate the AMR?
Phagocytosis is a process by which cells internalise solid matter, including microbial pathogens.
- Most cells are capable of phagocytosis, but it is the professional phagocytes of the immune system, including neutrophils, macrophages and dendritic cells, that truly excel in this process.
- In these cells, phagocytosis is a mechanism by which microorganisms can be contained, killed and processed for antigen presentation.
- This is a vital part of the innate immune response to pathogens, and plays an essential role in initiating the adaptive immune response.
Define Inflammation
Inflammation is the process whereby immune cells (which are normally distributed throughout the body) can be recruited and concentrated to a site of infection or damage.
What is caused by and what is released?
Following PAMP or DAMP recognition, PRRs trigger proinflammatory and antimicrobial responses by inducing the release of a broad range of cytokines from white blood cells.
What are the main events in inflammation?
The main events in inflammation are:
- Increased blood supply to the affected area;
- Increased permeability of the vasculature ;
- Migration of WBCs out of the blood capillaries into the affected tissue.
What is the adaptive immune system?
The adaptive immune system responds to infection. It takes days-weeks to develop the immune response, but it is:
- Potent;
- Responsive to any potential foreign entity;
- Highly specific; and
- Has memory.
Why is innate immunity important and what are the 4 cell types involved in this response?
The importance of adaptive immunity is that it provides a powerful defence against infection if the innate immune system is breached.
- Dendritic cells – capture, process and present antigens.
- T lymphocytes – control the immune response by providing “help” to B cells and macrophages (helper T cells); direct killing of infected or tumour cells (cytotoxic T cells).
- Cytokines – soluble proteins secreted mainly by T cells that control activities of other cells.
- B lymphocytes – produce and secrete antibodies, proteins that specifically bind target molecules (antigens) on microbes or cells.
What is the lymphoid and what is primary lymphoid organs and secondary?
• Immunological cells are largely organised into tissues and organs for best efficiency.
• Collectively, these structures are known as the lymphoid system.
1. Primary lymphoid organs are the sites of maturation of white blood cells – they differentiate from stem cells, multiply, are programmed and mature into functional cells.
2. Secondary lymphoid organs provide the site for interaction between antigens and WBCs. They also allow spread of the immune response.
3. Secondary lymphoid organs are associated with systemic and mucosal immune compartments (blue).
What is the lymphatic system?
carries lymph fluid and cells back into the bloodstream
What are the lymph nodes?
• At regular intervals along the lymph vessels are organised structures – lymph nodes
Lymph arrives at the node by an afferent lymphatic vessel, it filters through multiple layers of antigen presenting cells, T cells and B cells, and exits via the efferent lymphatic vessel.
The dense concentration of immune cells provides an ideal environment for initiating immune responses and communication between immune cells. Lymph nodes are common battleground sites for the immune system and infections.
What is the hallmark of adaptive immunity?
The ability to recognise pathogens.
What are two molecules involved in binding to antigens
Ig - made of glycoproteins, produced by plasma cells, bind to antigens to destroy pathogens and produced by B cells - humoral immunity
T-cell antigen receptors - Present on t-cells, recognise fragments of antigens, binding is weak, binding to an antigen peptide causes activation of t-cells - cellular immunity
