6- response to infection Flashcards
non specific immune response
• This is the body’s first line of defence against infection.
• It is non-specific, meaning it doesn’t target specific pathogens.
non specific immune response components
- physical barriers
- phagocytosis
- chemical defences
- fever
- inflammatory response
non specific immune response components- physical barriers
Skin and mucous membranes prevent pathogens from entering the body.
non specific immune response components- phagocytosis
Neutrophils and macrophages engulf and destroy pathogens.
non specific immune response components- chemical defences
• Stomach acid, saliva, and tears destroy pathogens.
• Lysozyme, which is found in secretions such as tears and mucus, kills bacterial cells by damaging their cell wall.
non specific immune response components- fever
The hypothalamus increases body temperature. This decreases the speed of pathogen reproduction and increases the rate of specific immune response.
non specific immune response components- inflammatory response
Increase in blood flow and immune cell recruitment to control infection at site.
specific immune response
• This is the body’s second line of defence, activated when innate immunity is insufficient.
• It is specific, meaning it targets specific pathogens based on their antigens.
components involved in specific immune response
• Lymphocytes.
• Antibodies → Produced by B cells, these proteins bind to specific antigens on the pathogens, marking them for destruction.
granulocytes
- neutrophil
- eosinophil
- basophil
neutrophil
rapid response
neutrophil primary function
First responders in acute inflammation.
neutrophil characteristics
• Most abundant type of white blood cell.
• Multilobed nucleus.
• Short-lived and highly mobile.
• Possess granules containing enzymes and antimicrobial peptides.
neutrophil role in immune response
• Engulf and destroy pathogens through phagocytosis.
• Release DNA and antimicrobial substances to trap and kill microbes via Neutrophil
Extracellular Traps (NETs).
eosinophil
kills parasites
eosinophil primary function
• Protects the body from parasites, allergens, and pathogens.
• Involved in asthma.
eosinophil characteristics
• Bilobed nucleus.
• Granules contain enzymes to destroy parasites.
eosinophil role in immune response
Release mediators that can either amplify or suppress inflammation.
basophil
inflammation
basophil primary function
Protects the body from parasites, allergens, and pathogens.
basophil characteristics
• Least common granulocyte.
• Large granules that stain dark blue with a basic dye.
• Contain histamine, which promotes blood flow to tissues.
basophil role in immune response
• Release histamine and other mediators in allergic reactions.
• Release substances that attract eosinophils and neutrophils to a site of infection.
monocytes
- macrophage
- dendritic cell
- lymphocytes
macrophage
longer lasting
macrophage primary function
Engulf and digest pathogens (phagocytosis).
macrophage characteristics
• Large white blood cells found in tissues throughout the body.
• Long-lived and less mobile than neutrophils.
• Play a key role in tissue repair and regeneration.
macrophage role in immune response
• Engulf and degrade cellular debris and pathogens.
• Present antigens to T cells to start adaptive immune response.
dendritic cell
relays info
dendritic cell primary function
Act as messengers between the innate and adaptive immune systems.
dendritic cell characteristics
• Possess long, branched projections called dendrites.
• Present in tissues that are exposed to the external environment, like skin.
dendritic cell role in immune response
• Engulf pathogens and present their antigens to T cells, for adaptive immunity.
• Promote T cell responses to antigens and stimulate the immune response.
lymphocytes
specific targeted response
lymphocytes primary function
Integral part of the adaptive immune system.
lymphocytes characteristics
• Smallest white blood cells, large nucleus.
• Main cells of the adaptive immune system.
• Include B cells, T cells, and Natural Killer (NK) cells.
• Long-lived and highly specific.
B cell role in immune response
Recognise antigens and produce antibodies to neutralise the pathogens.
T helper cells role in immune response
• Helper T cells → Recognise antigens presented by antigen-presenting cells, stimulate B cells and cytotoxic T cells.
• Cytotoxic T cells → Recognise and kill infected cells.
memory cell role in immune response
Long-lived T and B cells that remember the same pathogen for a faster response in future infections.
natural killer cells role in immune response
Kill infected and cancerous cells without prior sensitisation to antigens.
the humoral immune response
• Part of the adaptive immune system that involves the production of antibodies by B cells.
• Overall, this process ensures a targeted and effective response to specific pathogens, and provides long-lasting immunity due to the production of memory cells.
the humoral immune response process
• APCs capture pathogens, and present the antigens on their surfaces using MHC II OR…
B cells recognise antigens, and present the antigens on their surfaces using MHC II.
• T helper cells’ CD4 receptors recognise the antigen-MHC complex.
• T helper cells release cytokines that stimulate proliferation and differentiation of B cells.
• B cells proliferate by clonal expansion and differentiate into plasma and memory B cells.
• Plasma cells secrete large quantities of antibodies.
• Memory B cells provide long lasting immunity.
agglutination
Microbes clump together, making phagocytosis easier.
opsonisation
Antibodies coat microbes, marking them for phagocytes.
lysis
Bursting of bacterial cells.
precipitation/ neutralisation
Soluble toxins are made insoluble.
the cell mediated response
Part of the adaptive immune system, primarily involving T cells. It targets and eliminate cells that are infected with pathogens or are otherwise abnormal.
the cell mediated response process
• APCs capture pathogens, and present the antigens on their surfaces using MHC OR…
Infected host cells present the antigens on their surfaces using
MHC.
• T cells’ CD4 or CD8 receptors recognise the antigen-MHC complex.
• T cells differentiate into cytotoxic, helper, and memory T cells.
• Cytotoxic T cells directly kill infected cells by releasing cytotoxic granules that induce apoptosis in target cells.
• Helper T cells support other immune cells through cytokine release.
• Memory T cells provide long lasting immunity.
role of T and B memory cells
• Provide quicker and stronger immune response upon re-exposure to the same pathogen.
• Formation during initial exposure:
During the first encounter with a pathogen, specific T and B cells proliferate and differentiate into effector and memory cells.
• Rapid response upon re-exposure:
Memory cells respond faster and more effectively upon re-exposure to the same pathogen, leading to quicker elimination.
B memory cells
• Vital for humoral immunity.
• Recognition of antigens: B memory cells recognise antigens directly without the need for presentation by other cells.
• Activation and proliferation: Upon antigen recognition, they rapidly proliferate and differentiate into plasma cells.
• Role of plasma cells: They produce a large amount of specific antibodies that can neutralise pathogens or target them for destruction by other immune cells.
T memory cells
• Have a crucial role in cell-mediated immunity.
• Recognition of antigens: T memory cells recognise antigens presented by
MHC molecules on the surface of infected cells.
• Activation and proliferation: Upon antigen recognition, they rapidly proliferate and differentiate into effector
T cells.
• Role of effector T cells: They can directly destroy infected cells (cytotoxic T cells) or help B cells and other immune cells (helper T cells).
natural immunity
Acquired through normal life experiences.
artificial immunity
Acquired through medical interventions like vaccines or treatments.
active immunity
Involves the recipient’s own immune system and results in the production of memory cells. It takes time to develop but provides long-lasting protection.
passive immunity
Involves the transfer of antibodies from an immune individual to a non-immune individual. It provides immediate protection but is temporary as it does not involve the recipient’s immune response or the production of memory cells.
example of natural active immunity
Results from infection and recovery. The immune system responds to a pathogen, generating memory cells for future protection.
example of natural passive immunity
Transferred naturally from mother to foetus or infant. For example, antibodies are transferred through the placenta, providing temporary protection to the infant.
example of artificial active immunity
Achieved through vaccination.
Vaccines contain weakened or inactivated pathogens or their components, stimulating an immune response without causing the disease, leading to the formation of memory cells.
example of artificial passive immunity
Provided by administering antibodies, such as in antivenom or immunoglobulin therapy. This gives immediate, but temporary, protection as the recipient’s immune system is not actively involved and no memory cells are generated.
how vaccines work
• Vaccines use weakened, inactivated, or parts of pathogens to trigger an immune response without causing the disease itself.
• Immune response from vaccination results in production of memory cells for faster and more effective response to future encounters with the same pathogen.
benefits of vaccines
• Vaccination can prevent diseases, lessen disease symptoms if infection occurs, and reduce disease transmission rates.
• Large-scale vaccination programmes have contributed to eradicating or significantly reducing diseases, such as smallpox and polio.
concept of herd immunity
Herd immunity is a form of indirect protection from infectious diseases that occurs when a large percentage of a population is immune, slowing or stopping disease spread.
importance of concept of herd immunity
Herd immunity protects those who cannot receive vaccines due to certain health conditions, allergies to vaccine ingredients, or age restrictions.
potential issues in unvaccinated populations
- lower herd immunity
- vulnerability of at risk individuals
- re-emergence of diseases
- strain on healthcare systems
- evolution of new strains
potential issues in unvaccinated populations- lower herd immunity
If vaccination rates fall below the threshold required for herd immunity, the disease can spread more easily, causing outbreaks.
potential issues in unvaccinated populations- vulnerability of at risk individuals
Those who cannot be vaccinated due to specific health conditions become more vulnerable to infections when herd immunity is compromised.
potential issues in unvaccinated populations- re-emergence of diseases
Diseases that were once under control or eradicated can resurface in communities with low vaccination rates.
potential issues in unvaccinated populations- strain on healthcare systems
Increased disease outbreaks can overburden healthcare systems, leading to increased healthcare costs and lower quality of care for all patients.
potential issues in unvaccinated populations- evolution of new strains
High transmission rates can provide more opportunities for the pathogen to mutate and evolve into new, possibly more virulent or vaccine-resistant strains.
