Histology: Innate & Adaptive Immunity Flashcards
What are neutrophils? (2)
50% of white blood cells
> first to respond against bacteria/viral invasion
> alert other cells in immune system to respond as well
What are eosinophils? (3)
1% in blood stream
> respond to parasite(worms) infections
> role in allergy symptoms—> overreaction to mistaken invader-pollen
>highly concentrated in digestive tract
What are basophils?
1% of white blood cells
> mount non-specific immune response to pathogens
What are lymphocytes? (2)
> T-cells kill foreign invaders directly
> B-cells hum oral immunity, produce antibodies that “remember” an infection
What are monocytes?
Monocytes: 5% of white blood cells
> important for migrating into tissues and cleaning up dead cells
What is the process of blood clotting? (6)
- Blood vessel is damaged—> collagen becomes exposed
- Collagen exposure attracts platelets to the injured area
- Platelets aggregate & stick together to form a plug
- Platelet plug alone is not strong enough—> protein fibrinogen becomes exposed to unknown chemicals on outside of blood vessel and is turned to sticky fibrin proteins
- Fibrin Fibres form a sticky mesh allowing for other things to stick/attach to it—> reinforcing it even further
- This clot develops into a scab—> new skin forms beneath the scab until the scab degrades
What is scleroderma? (4)
Chronic hardening and tightening of the skin and connective tissues
- Excessive production of fibrillar collagen
- Changes in the physical structure of connective tissue components
- Localised (non-systematic)- skin limited
- Systematic sclerosis- affect internal organs
What happens when a hematopoietic stem cell divides?
- can divide indefinitely producing 1 daughter cell that remains a stem cell & another cell that adopts a specialised function
What do stem cells replenish?
- Replenish body’s blood cell population
-Cell division of stem cells from bone marrow give rise to 2 specialised sets of cells: (2)
> Lymphoid progenitor cells: give rise to immune cells—> Lymphocytes (B&T cells)
Myeloid progenitor creels: give rise to other immune cells(WBCs), erythrocytes & platelets
What is innate & adaptive immunity?
↳ Innate & adaptive immunity -
Recognition & response rely on traits common to groups of pathogens :
Pathogens → agents that cause disease (bacteria, viruses, fungi etc.)
Specialised dedicated cells of the ____ _____ enable animals to avoid or limit many infections.
immune system
What does the first line of defence do?
° First lines of defence > help prevent pathogens from entering the body.
↳ integumentary system
↳ mucosa
What are the 2 types of molecular recognition → that allow detection of foreign
molecules, particles } cells?
↳ innate recognition
↳ adaptive recognition
What is innate immunity?
→ innate immunity : a defence active immediately upon infection
What is adaptive immunity?
Adaptive immune response: activated after the innate response & develops more slowly.
What are self-particles? (2)
• made by your body /part of
• found circulating blood / attached to different tissues
• should not be targeted he destroyed by the immune system
↳ ‘tolerance’
What are non-self-particles? (2)
→ ‘foreign’} recognised as potentially harmful
• bacteria, viruses, parasites, pollen, dust, toxic chemicals 4 fungi
• infectious /pathogenic particles make proteins called Antigens
What are non-self-particles? (2)
→ ‘foreign’} recognised as potentially harmful
• bacteria, viruses, parasites, pollen, dust, toxic chemicals 4 fungi
• infectious /pathogenic particles make proteins called Antigens
What are antigens?
allow the human body to know that they intend to cause damage
• ‘name tag’ for each pathogen to announce its presence to the immune system
What are cytokines? (3)
molecules used for cell -signaling / cell-to-cell communication
° similar to chemokines → can be used to communicate with neighboring /
distant cells to initiate an immune response
° used to trigger cell trafficking /movement to a specific area of body
What are chemokines? (2)
type of cytokine
☐ released by infected cells
☐ infected host cells release chemokines in order to initiate an immune response } warn neighbouring cells of the threat
What does innate immunity rely on? (3)
Relies on:
- Dedicated immune system cells—> enable animals to avoid/limit infections
- First lines of defence (integumentary system + mucosa)—> help prevent pathogens from
gaining entry into the body
- Two types of molecular recognition within the body—> allow detection of non-self (foreign) molecules, particles and cells
What do barrier defences include? (4)
- include skin + mucous membranes of respiratory, urinary & reproductive tracts
- mucous—> traps + allows for removal of microbes
- many bodily fluids (saliva, mucous, tears)—> hostile to many microbes
- low pH of skin + digestive system—> prevents the growth of many bacteria
What do cellular defences include? (4)
- Lymphatic system
- Innate immune cells:
> Detect
> Devour
> Destroy - Recognise groups of pathogens using Toll-like receptors (TLR’s)
- TLR’s—> recognise fragments of molecules and characteristics of a set of pathogens
What do phagocytes do? (2)
- Phagocytes circulate throughout the body, looking for potential threats, like bacteria and
viruses, to engulf and destroy. - Security guards on patrol
What are the two main types of phagocytes?
Neutrophils
Macrophages
Where do neutrophils circulate?
circulate in blood
Why are phagocytic cells classified as granulocytes?
- phagocytic cells that are also classified as granulocytes because they contain granules in their cytoplasm.
- granules are very toxic to bacteria and fungi, and cause them to stop proliferating or die on contact
What is the function of neutrophils?
- first cells to arrive at the site of an infection because there are so many of them in circulation at any given time
Where do macrophages reside?
- migrate through body/reside in organs + tissues
What is the function of macrophages? (3)
- can leave the circulatory system by moving across the walls of capillary vessels.
- ability to roam outside of the circulatory system is important—> allows macrophages to hunt pathogens with less limits
- release cytokines in order to signal and recruit other cells to an area with pathogens
What is the function of dendritic cells? (4)
- stimulate development of adaptive immunity
- antigen-presenting cells
- since dendritic cells are located in tissues that are common points for initial infection—> can identify threats and act as messengers for the rest of the immune system by antigen presentation
- act as bridge between the innate immune system and the
adaptive immune system
Where are dendritic cells located? (5)
- external environments through the skin
- inner mucosal lining of the nose
- lungs
- stomach
- intestines
What is the function of eosinophils? (4)
- discharge destructive enzymes against parasite
- granulocytes target multicellular parasites
- secrete a range of highly toxic proteins and free radicals that kill bacteria and parasites
- use of toxic proteins and free radicals also causes tissue damage during allergic reactions—> so activation and toxin release by eosinophils is highly regulated to prevent any unnecessary tissue
damage
Where are eosinophils located? (5)
- the thymus
- lower gastrointestinal tract
- ovaries, uterus
- spleen
- lymph nodes
Where are mast cells found? (2)
Found in mucous membranes and connective tissues
What is the function of mast cells? (4)
- important for wound healing and defense against pathogens via the inflammatory response
- when mast activated—> release cytokines and granules that contain chemical molecules to create an inflammatory cascade
- Mediators—> histamine, cause blood vessels to dilate, increasing blood flow and cell trafficking to the area of infection
- The cytokines released during this process act as a messenger service, alerting other immune cells, like neutrophils and macrophages, to make their way to the area of infection/ be on alert for circulating threats
What is the function of basophils? (3)
- granulocytes that attack multicellular parasites
- release histamine—> like mast cells
- use of histamine makes basophils and mast cells key players in mounting an allergic response
What are natural killer cells? (4)
- circulate throughout body + detect abnormal cells
- release chemicals leading to cell death—> inhibits spread of vitally infected/ cancerous cells
- do not attack pathogens directly—> destroy infected host cells in order to stop the spread of an infection
- Infected or compromised host cells can signal natural kill cells for destruction through the expression
of specific receptors and antigen presentation
What is the process of a local inflammatory response? (5)
- brought by molecules released upon injury + infection
- mast cells(immune cells found in connective tissue —> check above for more info) —> discharge cytokines(signalling molecules that recruit neutrophils to the site & release histamine(triggers blood vessels to dilate + become more permeable ) —> increasing blood supply which triggers inflammatory response
- cycles of signalling + response continues inflammation process
- enhanced blood flow to site—>helps deliver anti-microbial peptides
- results in accumulation of pus—>fluid rich in WBCs, dead pathogens & debris from damaged tissue
What is the end result of a local inflammatory response? (4)
—> pus + excess fluid taken up as lymph
—> fluid transported in body by lymphatic system
—> lymph nodes(throughout body): contain macrophages which engulf pathogens that enter lymph
—> Dendritic cells migrate to lymph nodes after interacting with pathogens & stimulate adaptive immunity
What can more extensive tissue damage/infection lead to?
- more extensive tissue damage/infection —> can lead to a systemic response (throughout body)
What happens when a B cell encounters an antigen?
When a naive B cell encounters an antigen that fits or matches its membrane-bound antibody, it quickly divides in order to become either a memory B cell or an effector B cell, which is also called a plasma cell. Antibodies can bind to antigens directly.
What is the role of T cells? (7)
- Once formed in the bone marrow—>T progenitor cells migrate to the thymus (hence the name “T cell”) to mature and become T cells.
- While in the thymus—>developing T cells start to express T cell receptors (TCRs) and other receptors called CD4 and CD8 receptors.
- All T cells express T cell receptors, and either CD4 or CD8, not both.
- So, some T cells will express CD4, and others will express CD8.
- Unlike antibodies, which can bind to antigens directly, T cell receptors can only recognize antigens that are bound to certain receptor molecules, called Major Histocompatibility Complex class 1 (MHCI) and class 2 (MHCII).
- These MHC molecules are membrane-bound surface receptors on antigen-presenting cells, like dendritic cells and macrophages.
- CD4 and CD8 play a role in T cell recognition and activation by binding to either MHCI or MHCII
What is the process of proliferation? (7)
- In the body there are few lymphocytes with antigen receptors specific for any particular epitope
- In the lymph nodes—>antigen is exposed to a steady stream of lymphocytes until a match is made
- This binding of a mature lymphocyte to an antigen initiates events that activate the lymphocyte bearing the receptor
- Once activated—>B or T cell undergoes multiple cell divisions (clonal selection) to produce a clone
of identical cells - Some cells from the clone become effector cells that act immediately against the antigen
- Effector cells are plasma cells that secrete antibodies
- The remaining cells in the clone become long-lived memory cells that can give rise to effector cells if the same antigen is encountered again
A typical adaptive immune response includes several steps: (6)
- ) The antigen for the pathogen is taken up by an antigen-presenting cell (APC), such as a dendritic cell or macrophage, through phagocytosis.
- ) The APC travels to a part of the body that contains immature T and B cells, such as a lymph node.
- ) The antigen is processed by the APC and bound to MHC class II receptors and MHC class I receptors on the cell membrane of the APC.
- ) The antigen is presented to immature helper T cells and cytotoxic T cells through binding the MHC II (helper T) or MHC I (cytotoxic T) to T-cell receptors.
- ) These T lymphocytes mature and proliferate. Helper T cells activate B cells, which proliferate and produce antibodies specific to the antigen, while cytotoxic T cells destroy pathogens that bear the antigen that was presented to them by the APCs.
- ) Memory B and T cells are formed after the infection ends.
What is the primary immune response?
~ Primary immune response—> first exposure to specific antigen—> clone of
lymphocytes—> formed that are specific to the pathogen
What is the secondary immune response?
~ Secondary immune response—> memory cells facilitate a faster, greater and
more prolonged response from a reservoir of T&B memory cells.
Adaptive immunity defends against infection of body fluids and body cells
• The defenses provided by B and T lymphocytes can be divided into the ______ immune response and the _____-_____ immune response.
humoral
cell-mediated
Describe the process of how T cells activate adaptive immunity? (4)
- Antigen-presenting cells have class I and II MHC molecules on their surfaces
- Class II MHC molecules provide a molecular signature by which antigen presenting cells are recognised
- Antigen receptors on the surface of helper T cells bind to the antigen and the class II MHC molecule; then cytokine signals are exchanged between the two cells
- The helper T cell is stimulated to produce its own set of cytokines
How is the helper T cell activated by a dendritic cell? (9)
- In the tissue fluid, cells of the second line of innate defense such as dendritic cells carry out
surveillance for any foreign objects - Dendritic cells engulf the virus/foreign body with an endosome—> fuses with a lysosome whose
enzymes digest the virus - resulting fragments of virus after digestion —>epitopes
- dendritic cell then attaches to virus epitopes to presentation molecules called —> MCH II
- this complex fold outwards so that it sits on outside of dendritic cell membrane
- dendritic cell then enters a lymphatic vessel— >travels to nearby lymph node—> debtritic cell part of innate immune defenses & counters a helper T cell which is part of adaptive defenses
- The T cell receptor—> TCR of this helper T cell recognises the virus epitope
- while the CD4 glycoprotein associated with TCR recognises the MCH II
- dendritic cell then stimulates activation of this helper T cell
Describe the entire process of humoral immune response.
- Antibodies help neutralize/eliminate toxins and pathogens in the blood + lymph
- Characterised by the secretion or antibodies by clonally selected B cells
- Begins with B cell activation
- B cell activation involves helper T cells & proteins on the surface of the pathogens
- When an antigen binds a B cell, the cell takes in a few foreign molecules by receptor mediated endocytosis
- The class II MHC protein of the B cell then presents an antigen fragment to a helper T cell, a process that is critical to B cell activation
How do cytotoxic t cells use toxic proteins to kill cells infected by viruses or other intracellular pathogens?
- Cytotoxic T cells recognise fragments of foreign proteins produced by infected cells
- The activated cytotoxic T cell secretes proteins that disrupt the membranes of target cells and trigger apoptosis (cell death)
