Respiratory Immunology 5: Vaccination Flashcards
(45 cards)
What is vaccination, why is it done and how is the effect achieved?
Deliberate exposure to an antigen in order to induce immunologically mediated resistance to disease, through induction of memory
Generation of immunological memory?
Stimulation and maturation of the immune response after exposure to an antigen, such that is able to respond immediately and robustly upon re-exposure
Generation of memory B cells?
Long-lived MEMORY B CELLS are generated during primary humoral immune responses
Memory B cells can survive in a dormant state for many years after antigen has been eliminated
Memory B cells rapidly re-activate in response to a second encounter with that specific antigen - clonal expansion, differentiation into plasma cells, antibody production
Impact of memory on antibody production?
Primary infection - during incubation period, IgM antibody being produced and IgG antibody is produced later on, towards the end of clinical disease presentation
Secondary infection - IgG antibody produced immediately due to memory B cells and so clinical features do not present
Describe secondary antibody response
Pre-existing IgG antibody results in ability to clear during incubation periods:
Direct action to neutralise bacteria and bacterial products
Rapid mobilisation of phagocytes and complement
Pre-formed IgA blocks bacterial attachment to mucous membranes`
Clearing of toxin in Diphtheria?
Individual may clear toxin through anti-toxin antibodies, but remain a carrier of micro-organism
How is T cell memory generated through vaccination?
Vaccination simulates rare naive T cells and induces a strong T cell response in 14-21 days; some become EFFECTOR T cells which:
Mostly die by apoptosis in absence of persisting antigen
Smaller number become MEMORY CELLS and are maintained at low frequency
Memory T cell characteristics?
Make a MORE EFFECTIVE IMMUNE RESPONSE:
Primed CD8 T cells can immediately kill without immunological “help”
Primed CD4 T cells can produce cytokines immediately
Have enhanced properties of cell adhesion and chemotaxis - memory cells can access non-lymphoid tissues effectively, where bugs actually are
LONGEVITY - memory T cells can be maintained for a long time without antigen
How long does memory last?
A long time - e.g: re-exposure to measles virus is unnecessary in maintaining memory
Types of vaccination?
Difference between immunisation and vaccination?
Immunisation - process through which an individual develops immunity/memory to a disease (inc. both deliberate and natural infection)
Vaccination - deliberate administration of antogenic material to produce immunity to a disease
What is active immunity?
Protection produced by the person’s own immune system; can be stimulated by vaccine/naturally acquired infection and is usually permanent
What is passive immunity?
Protection transferred from another person or animals but is temporary and wanes with time
Describe active vaccination
Stimulates immune response to antigen through SAME PATHWAYS AS NATURAL INFECTION; thus generates immunity and memory similar to natural infection
MORE SIMILAR A VACCINE IS TO DISEASE-CAUSING FORM OF ORGANISM, BETTER THE IMMUNE RESPONSE TO DISEASE IS
Methods for generating immunological memory?
Exposure of an individual to INFECTIOUS ORGANISM ITSELF
Exposure to a SIMILAR PATHODEN that is LESS VIRULENT
Exposure to the INACTIVATED PATHOGEN
Exposure to a LESS VIRULENT VERSION of the SAME PATHOGEN
What is variolation?
Predecessor of vaccination - exposure to contents of dried smallpox pustules from infected patient, optimally from people with less severe disease 1:100 died
Principle of exposure to a similar but less virulent pathogen?
One disease is being induced to generate cross-reactive immunity against another disease
Example of exposure to a similar but less virulent pathogen?
Immunisation with cowpox protecting against smallpox as:
Molecular similarities between cowpox and smallpox
Antibodies generated through exposure to cowpox cross-react with smallpox, neutralising the smallpox virus
Inactivated vaccines AKA?
ATTENUATED or killed (not a good term as some inactivated vaccines are made from components and were not alive before) vaccines
Key features of inactivated vaccines?
Cannot replicate but generally not as effective as live vaccines
Immune response PRIMARILY ANTIBODY-BASED (not T cells); antibody titre may diminish with time and may require MULTIPLE DOSES to stimulate immune response
How to make an inactive vaccine from a live pathogen?
Expose pathogen to chemical fixative, e.g: formalin, heat denaturation or irradiation
Problems with inactive vaccines?
Under-activation - leaves viable pathogens/toxins within organism
Over-activation - loss of tertiary structure and conformational antibody binding sites
What is poliomyelitis?
Caused by POLIO VIRUS, which is transmitted via oro-faecal route
Clinical presentation of poliomyelitis?
90-95% of infections are asymptomatic - may still transmit disease
5% have minor flu-like illness
0.5% cases develop muscle weakness and paralysis - may develop post-polio syndrome
