immunity lowkey Flashcards
What are the types of non-cellular pathogens?
Viruses and prions
Give two examples of physical barriers in plants
Waxy cuticles on leaves to prevent pathogenic entry.
Presence of thorns or trichomes to deter insects and grazers.
Give two examples of chemical barriers in plants
Oxalic acid, toxic to some organisms if ingested.
Chitinases, enzymes that have antifungal properties.
Give two examples of physical barriers in animals
Intact layer of dead skin which prevents pathogens from infecting live cells.
Mucus secretions which trap pathogens and prevent orificial entry.
Give two examples of chemical barriers in animals
Lysozymes in tears have antibacterial properties and prevent bacterial invasion.
Stomach acid, very low pH destroys many pathogens by denaturing the functional tertiary structures of their essential enzymes.
What are phagocytes and how do they work?
Phagocytes are leukocytes that engulf non-self cells by endocytosis and digest them using lysosomes.
What are the three types of phagocytes?
Neutrophils, Macrophages, Dendritic cells.
What are cytokines?
Cytokines are signalling molecules that stimulate, recruit, and proliferate immune cells and guide them to sites of infection or injury.
What are macrophages?
Macrophages are phagocytes that engulf pathogens and display pathogenic antigens on their surface MHC II markers.
What are the three types of antigen presenting cells?
Macrophages, B- cells and dendritic cells.
What are dendritic cells?
Dendritic cells are phagocytes that engulf pathogens and display pathogenic antigens on their surface MHC II markers.
What are natural killer cells?
Natural killer cells are immune cells that identify and destroy abnormal or cancerous cells by detecting missing/abnormal MHC I markers on their surface.
- found in blood/lymph
- kill virus-infected cells
What are interferons?
Interferons are cytokines released from virally infected cells that interact with receptors on normal cells and make them less susceptible to viral infection.
- signal change in plasma membrane making entry of virus more difficult (make PM less fluid)
- signals neighbouring uninfected cells to prepare to destroy RNA to reduce protein synthesis
- signal neighbouring infected cells to undergo apoptosis
- activates immune cells such as NK cells
What are the three major outcomes of a complement cascade?
Opsonisation, Chemotaxis, Lysis
What is a complement cascade?
A complement cascade is activated when they make direct contact with molecules on the surface of pathogens
- it is a series of complex reactions where complement proteins interact with each other to deal with pathogens, and can result in opsonisation, chemotaxis, or lysis
Describe the process of opsonisation.
Opsinisation occurs when antibodies or complement proteins stick to the surface of pathogens flagging them for phagocytosis.
Describe the process of chemotaxis.
Chemotaxis is the process of complement proteins gathering near pathogens to attract phagocytes to them, increasing the chances of phagocytosis
Describe the process of lysis with respect to complement proteins.
Lysis occurs when complement proteins join together and form a membrane attack complex (MAC), which creates membranal pores and destroys the pathogen cell.
What are the three main stages of inflammation?
- Initiation
- Vasodilation
- Migration
What occurs during vasodilation with respect to inflammation?
During vasodilation, histamine released from mast cells causes blood vessels to dilate and increases blood flow to injury site, which can cause swelling, redness and warmth associated with inflammation.
What occurs during migration with respect to inflammation?
During migration, phagocytes are guided by cytokines to the site of injury and complement proteins opsonise pathogens to increase chances of phagocytosis, platelets travel to the site to block wounds → important for clotting,
- pus indicates that this stage is occurring
–> consists of mainly dead immune cells, tissue and pathogens
What are the three main roles of the lymphatic nervous system?
- Transportation of antigen-presenting cells to secondary lymphoid tissues for antigen recognition and initiation of the adaptive immune response.
- Production of leukocytes
- Removal of fluid from tissues around the body.
What are the three major components of the lymphatic nervous system?
- Primary lymphoid tissues
- Secondary lymphoid tissues
- Lymphatic vessels
Where are B and T cells produced?
B and T cells are produced in primary lymphoid tissues found in bone marrow.
What are the main secondary lymphoid tissues?
- Lymph nodes
- Spleen
What are the main primary lymphoid tissues?
- Bone marrow
- The thymus
How is the adaptive immune response initiated?
The adaptive immune response is initiated by:
- the selection of T-helper cells
→ phagocytosis occurs and the antigen-presenting cell displays the specific pathogenic antigens on their surface via MHC II markers to activate corresponding T-helper cells
- This can lead to either the humoral or cell-mediated immune responses.
brief outline of the humoral immune response.
- Antigen presenting cells display pathogenic antigens on their cell surface to activate helper T-cells and initiate the humoral immune response.
- Helper T release cytokines activating B cells which bind to the same antigen in secondary lymphoid tissues and express them via MHC II markers on their surface.
- Selected helper T-cells recognise and bind to the selected B cell and release cytokines to make the B cell undergo clonal expansion and differentiate into either plasma or B memory cells.
- Plasma cells produce antibodies specific to the selected antigen, and are secreted into the bloodstream to defend against the pathogen. Memory B cells remain in lymphoid tissues and can divide into plasma cells if reinfection occurs.
What is the function of plasma cells?
Plasma cells produce antibodies that are specific to the antigen that activated their B cell and helper T cell, which get secreted into the blood to defend against extracellular pathogens and other foreign material.
What is the function of memory B cells?
Memory B cells provide long-lasting immunity and remain in lymphoid tissues for long periods of time while releasing low amounts of antibodies, and can also rapidly divide into plasma cells if reinfection occurs for a faster adaptive immune response.
What are the cellular components of the second line of defense?
Neutrophil, macrophage, dendritic cell, natural killer cell, mast cell, eosinophil cells
Outline how natural killer cells detect and destroy pathogenic cells.
- Killer activation receptors on natural killer (NK) cells bind to cellularly stressed cells.
- Killer inhibitory receptors examine the cell’s surface for MHC I markers to bind to.
- If there are insufficient MHC I markers on the cell, killer inhibitory receptors cannot bind and cell death is initiated via apoptosis.
Outline the cell-mediated immune response.
- Antigen presenting cells display pathogenic antigens on their surface via MHC II markers to activate helper T-cells, while simultaneously they encounter a naive T-cell with matching antigens.
- The selected T-cell is stimulated by cytokines to undergo clonal expansion and differentiate into cytotoxic T cells and memory T cells.
- Cytotoxic T cells can recognise abnormal proteins on infected cells, destroying them by secreting chemicals to induce apoptosis.
- Memory T cells provide long lasting immunity and remain in lymphoid tissues and can rapidly divide into helper and cytotoxic T cells if the pathogen is re-encountered for a faster adaptive immune response.
What is artificial immunity?
Artificial immunity is immunity conferred through medical intervention.
What is active immunity?
Active immunity is immunity conferred by antibodies and memory cells produced by one’s own adaptive immune system.
What is the role of the first line of defence?
The first line of defence is responsible for preventing or impeding the entry of a pathogen into an organism
Why is the adaptive immune response slower than the innate immune response?
The adaptive immune response is slower than the innate immune response because it requires time to recognize specific pathogens, activate specialized immune cells and form immunological memory for a precise response. In contrast, the innate immune system is active all the time and provides immediate but nonspecific defence
Outline the process of becoming allergic.
- Allergen is ingested or inhaled and recognised as non-self by the immune system.
- The adaptive immune system activates and B cells produce IgE antibodies.
- IgE antibodies attach to mast cells, priming them and sensitising the individual to the allergen.
- During reexposure to the allergen, the mast cells are triggered and release lots of histamine which results in an inflammatory response.
