2.5 b Flashcards
What are non-specific immune responses of mammals?
- physical barriers
- chemical secretions
- inflammatory response
- phagocytes
- natural killer cells
What are examples of physical barriers?
skin epithelial tissue, tears, earwax, mucus/mucosal membranes
What are examples of chemical barriers?
hyrolytic enzymes in mucus, lyzozyme in tears, hydrochloric acid in stomach, urine (acdic), interferon - signal proteins made by hosts cells in response to viruses (blocks transcription of viral proteins)
What can saliva and tears do?
destory bacteria cell walls
What doe low pH environs do?
areas such as stomach, vagina and sweat glands denature cellular proteins of pathogens
What do injured cells release?
signalling molecules which result in enhanced blood flow to the site and bring antimicrobial proteins and phagocytes
What is the inflammatory response?
- chemicals incl. histamine and prostaglandins (cytokines) released causing blood vessels to leak fluid into tissues, causing swelling
- helps isolate foreign substance from further contact with body tissues
- chemicals also attract phagocytes
What is phagocytosis?
white blood cells carry out non-specific process, uses powerful enzymes contained in lysosomes, engulfs them and store inside vacuole, detect chemicals released by bacteria and move towards it, lysosomes within phagocyte fuse with and digest bacterial cell
Describe natural killer cells (NK)
- lymphocytes (white blood cell) identify abnormal cells (virus infected/cancerous)
- normal cells have major hisotcompatibility class I (MHC I) molecules on their surface
- abnormal cells MHC I molecules have latered expressions so target for NK cells
- NK’s identify and attach to cells virally infected, releasing chemicals leading to cell death by inducing apoptosis
What are lymphocytes?
white blood cells, mammals contain different ones, each receptor on surface which could recognise parasite antigen
What causes lymphocyte to divide?
antigen binding to receptor, creates clonal population
What do lymphocytes do?
some produce antibodies other induce apoptosis
What gives antibodies antigen specificity?
antibodies possess regions where amino acid sequence varies according to antigen
What are antigens?
proteins on all cells surface, if they don;t belong to host they are considered foreign
- includes molecules belonging to bacteria, viruses, fungi, parasitic worms and cells from transplanted tissues
What happens when antigen binds to antibody binding site?
antigen-antibody complex can result in parasite inactivation, rendering it susceptible to phagocytes or stimulating cell lysis
Why are memory cells important?
when they recognise an antigen, if it enters the body again, they produce many copies of the cell and quickly produce plasma cells which secrete antibody to destroy foreign antigens
What does initial antigen exposure do?
produces memory lymphocyte cells specific to it so secondary response is produced in the future
How is antibody production enhanced in secondary respone?
in terms of production speed, concentration in blood and duration in blood.
What does antigenic variation do for parasite?
allows change between different antigens during course of host infection, may also allow reinfection of same host with new variant
How can viruses escape immune surveillance?
by integrating their genome into host genomes, existing in an inactive state known as latency
- virus then activates again when favourable conditions arise
what is epidemiology?
the study of outbreak and pattern of infectious disease to determine spread factors
What are some disease spread factors?
- spread quicker through dense populations/areas of overcrowding
- some individuals genetically immune due to genetic variation
- resistant individuals present barrier to transmission, if high enough number of resistant individuals, an epidemic may be avoided
Explain herd immunity…
when resistant individuals ultimately provide a level of protection to non-immune population
- the threshold is density of resistant hosts
- number of resistant individuals may be increased by vaccinations
What does the herd immunity threshold depend upon?
- the disease
- the efficacy of the vaccine
- the contact parameters for the population
What are pros and cons of herd immunity and vaccination?
Pros
- protects vulnerable and un-vaccinated
- reducing spread of disease
Cons
- developing world: vaccination not possible due to malnutrition/poverty
- developed world: percentage of population rejects vaccine
How do vaccine work?
- contain antigens that elicit immune response
- contain a microorganism or virus in a weakened, live or killed state, or proteins/toxins from the organisms
What are challenges in vaccine treatment?
- some parasites difficult to culture in lab making vaccine design difficult
- rapid antigen change has to be reflected in vaccine design
- antigenic variation must be reflected
- similarities between host and parasite metabolism makes it difficult to fin drug compounds that only target the parasite
What conditions make coordinated treatment/control programs difficult to achieve?
overcrowding can occur in refugee camps due to war or natural disaster or rapidly growing cities in less economically developed countries (LEDCs)
What cans sometimes be the only practical control strategies?
civil engineering projects to improve sanitation combine with coordinated vector control
What are the benefits of improved parasite conrol?
reduce child mortality and result in population-wide improvements in child development and intelligence as individuals have more resources for growth and development
