Innate immunity Flashcards
innate vs adaptive immunity
phases of immune response
give examples of cells involved in innate immunity and adaptive immunity
extracellular pathogens vs intracellular pathogens
Phagocytosis steps
what are PAMPs - Pathogen Associated Molecular Patterns
PAMPs (Pathogen-Associated Molecular Patterns) are unique molecules found on the surface of pathogens like bacteria, viruses, and fungi. They act as “red flags” for the immune system to detect and respond to.
Examples of PAMPs include:
- LPS (lipopolysaccharide): Found on the outer layer of some bacteria.
- Flagellin: Found in bacterial flagella.
- Viral RNA/DNA: Unique to viruses.
The immune system recognises PAMPs using special receptors like Toll-like receptors (TLRs) to trigger a defence response.
what are DAMPs- Damage Associated Molecular Patterns
DAMPs (Damage-Associated Molecular Patterns) are molecules released by damaged or dying cells within the body. They signal the immune system to respond, even if no infection is present.
Examples of DAMPs include:
- ATP: Released when cells are damaged.
- DNA: Found outside cells (normally it stays inside).
- Heat-shock proteins: Produced under stress.
While PAMPs come from pathogens, DAMPs come from the body’s own cells, alerting the immune system to tissue injury or danger.
how does the innate immune system recognise threats
- Pathogen Patterns (PAMPs): The immune system spots unique molecules on pathogens, like bacteria or viruses, that don’t belong in the body.
- Damage Signals (DAMPs): When cells are damaged, they release signals that alert the immune system to come and help.
- Missing “Self” Markers: Healthy cells have markers (MHC) that say, “I belong here.” If a cell is missing these, immune cells like natural killer (NK) cells may destroy it, as it could be infected or abnormal.
what do Pattern recognition receptors do
They help the body spot and respond to pathogens (like bacteria) or damage
Families of receptors that exist to detect pathogens in fluids, cell surfaces and compartments, and intracellularly
where are pattern recognition receptors found
PRRs can be found on cell surfaces, inside cells, or floating in body fluids
types of pattern recognition receptors
- Secreted receptors: These float around in body fluids and detect pathogens (e.g., pentraxins, collectins).
- Surface and membrane receptors: These are on the outside of cells or inside cell compartments (e.g., Toll-like receptors or TLRs).
- Cytoplasmic receptors: These are inside cells and detect pathogens or damage directly (e.g., RLRs, NLRs).
six ways the innate immune system detects and responds to threats in the body
- PAMP-triggered immunity (PTI): The immune system detects molecules unique to pathogens, called PAMPs, to identify infections.
- Effector-triggered immunity (ETI): Some pathogens try to avoid detection. If they modify certain molecules, the immune system picks up on these changes and responds.
- Recognition of absence of self: The immune system notices if normal cell markers (like MHC) are missing, indicating a cell might be infected or abnormal.
- Recognition of altered self: If cell markers are present but altered, this signals that the cell might be stressed or infected.
- Damage recognition: The immune system detects signals (DAMPs) from damaged cells, prompting an immune response to address the injury.
- Surveillance: The immune system keeps watch for stress signals or harmful factors from pathogens, helping to maintain security and react to threats.
what is chemotaxis
Chemotaxis is the process where immune cells move toward the site of infection or injury. They are guided by chemical signals released by damaged cells or pathogens, helping the immune cells reach and fight off infections or start repairs.
what is extravasation (also called diapedesis)
process where immune cells (like neutrophils) move from the bloodstream into infected or injured tissues
extravasation (also called diapedesis) steps
- Chemokines Released: At the infection site, cells release chemical signals (chemokines) that attract neutrophils.
- Neutrophil Rolling: Neutrophils slow down and roll along the blood vessel wall, sticking to special molecules (like E-selectin) on the surface.
- Tight Binding: Neutrophils firmly attach to the blood vessel wall through stronger interactions with integrins and adhesion molecules.
- Squeezing Through: Neutrophils squeeze between the cells of the blood vessel wall and enter the tissue to reach the infection.
name 3 adhesion molecules and their role and tissue they act on
- Selectins: Help immune cells stick to blood vessel walls by binding carbohydrates. Found on activated endothelium (blood vessel lining) and platelets.
- Integrins: Enable strong binding to other molecules (like ICAM-1) and help immune cells move out of the blood vessels. Present on immune cells like monocytes, neutrophils, and T cells.
- Immunoglobulin Superfamily (e.g., ICAM-1): Act as binding partners for integrins, helping immune cells attach firmly to the vessel wall. Found on endothelium and activated immune cells.
name two types of receptors that help immune cells recognize and remove pathogens or dead cells
describe the phagocytic pathway
- Engulfment: The immune cell takes in the particle, forming an early phagosome (a bubble that contains the particle). The environment inside starts at a pH of 6.2.
- Acidification: The phagosome matures, and its pH drops to around 4.5-5.0, becoming a phagolysosome. Enzymes are added to help break down the particle.
- Digestion: The phagolysosome fuses with a lysosome (another cell structure filled with digestive enzymes) to fully break down the particle.
- Recycling: Useful materials are recycled back into the cell, while waste can be expelled or stored.
describe the phagosome maturation process
- Early Phagosome: The process starts with an early phagosome (pH 6.1-6.5), which contains the engulfed bacteria. It has proteins like Rab 5 and markers such as EEA1.
- Late Phagosome: As it matures, the phagosome’s pH lowers to 5.5-6.0. It now contains Rab 7 and LAMPs (lysosomal-associated membrane proteins), which prepare it for stronger digestion.
- Phagolysosome: Finally, the phagosome merges with a lysosome to form a phagolysosome (pH 5.0-5.5), where enzymes (hydrolases, cathepsins) and NADPH oxidase create reactive oxygen species (ROS) to break down the bacteria.
what are antimicrobial mechanisms used by phagocytes - differ between macrophages and neutrophils
examples of pathogens that have evolved multiple strategies to prevent and/or inhibit phagocytosis:
how does the innate immune system activate the adaptive immune system
- Dendritic Cells’ Role: Dendritic cells patrol tissues, looking for signs of infection or damage. When they detect something, they “mature” and travel to a nearby lymph node.
- Antigen Presentation: In the lymph node, dendritic cells present pieces of the pathogen (antigens) to naïve T cells to activate them.
- Two Signals for T Cell Activation:
- Signal 1: The dendritic cell presents the antigen on an MHC molecule to the T cell.
- Signal 2: It also provides a costimulatory signal through B7 proteins, which is necessary for full activation.
- T Cell Activation: With both signals, the T cell becomes activated, multiplies, and transforms into effector T cells that can fight the infection.
dendritic cells and macrophages.
B cells function
Typical antigen presenting cells function
- Dendritic Cells (DCs) and Macrophages:
- Eat (phagocytose) pathogens.
- Have receptors to detect pathogens and damaged cells.
- Move to lymph nodes to interact with T cells after activation.
- Present antigens on MHC class II molecules and provide additional activation signals for T cells.
- B Cells:
- Capture antigens using specific receptors (BCRs).
- Present antigens on MHC class II molecules.
- Also provide activation signals to T cells.
Mast Cells, Basophils, Eosinophils, and ILC3s - atypical antigen presenting cells function
- Can express MHC class II molecules but usually only in certain immune situations.
- Play roles in specific immune responses, like type 2 immunity (allergic responses).
- Less effective at directly activating naïve T cells in a specific way
innate vs adaptive vs immunological memory immune response time
