Week 2 - Immunity And Disease Flashcards
What are the different types of immunity?
Innate
Adaptive
What is innate immunity?
Defence mechanisms present even before infection or activated in a non-specific way
- skin, mucous membranes
- phagocytic cells (neutrophils,macrophages), inflammation, fever
What is adaptive immunity ?
- cell-mediated immunity
- humoral immunity
What are non-specific defences in the body?
- intact skin
- mucous and cilia
How is the skin a barrier to infection?
- outer layer = keratin - mechanical barrier
- dead skin cells constantly sloughed off (hard for bacteria to colonise)
- sweat and oils contain anti-microbial chemicals
What mucous membranes help prevent infections occurring?
- cilia - respiratory tract
- acid - stomach, vagina
- enzymes - saliva, eye
Name the granulocytes and what they do
Neutrophils, eosinophils and basophils
- remove dead cells and micro-organisms
- attracted by an inflammatory response of damaged cells
Name the monocytes and what they do
Macrophages
- in tissues which serve as filters trapping microbes
- macrophages live longer than granulocytes
- stimulate specific immune response (antigen-presenting)
How do macrophages create a non-specific response to infection?
- release protein signals - interleukin-1 (IL-1) and interleukin-6 (IL-6)
Name other non-specific responses to infections
- fever
- pain,swelling, redness
- acute-phase proteins released from liver (bind to bacteria and activate complement proteins)
What does specific/adaptive immunity rely on?
Antigens
-specific substances found in foreign microbes
What other types of cells in the lymphatic system are used in adaptive immunity?
Lymphocytes (b cells and T cells)
-carried in blood or lymph
Where are lymphocytes produced?
Bone marrow
-B-cells mature in bone marrow then concentrate in lymph nodes and spleen
T-cells mature in the thymus
What antigens do T-cells recognise?
Antigens presented by major histocompatibility complex - class I (all cells) or class II (APC)
What do T-cells do?
- directly attack invaders (cytotoxic, CD8+, MHC I)
- cell mediated immunity
- recognise pathogens that have entered cells
- also help B-cells (helper cells, CD4+, MHC II)
What do cytotoxic T-cells do?
- seek out and destroy any antigens in the system and destroy microbes tagged by antibodies
- some can recognise and destroy cancer cells
- variable region on T-cell receptor
What do T helper-cells do?
- stimulate B-cells
- activate cytotoxic cells and macrophages to attack infected cells
What is immunity?
Protection/defence against infections
How do T-cells recognise an invader?
- detect antigen on cell surface or epitope (fragment of antigen)
- if a non-self antigen protein is encountered by a macrophage, it will bring the protein to a helper t-cell for identification
- if helper t-cell recognises it as non-self an immune response is launched
What does HIV destroy?
Helper t-cells - so immune response diminished
What is the other name for helper t-cells?
CD4+
What do cytokines stimulate?
B-cell division
What do b-cells differentiate in to?
Memory and plasma cells
What do b-cells do?
- secrete antibodies (glycoproteins/specific, hypervariable region, different subtypes - IgG, IgM, IgA, IgE, IgD)
- humoral immunity
- recognise pathogens outside cells
- opsonisation, bind and block (agglutinate) stimulate complement
- become memory or plasma cells
What issues can occur with your immune system?
Immunodeficiency- prone to infections (chemo, drugs, HIV, splenectomy, bone marrow dysfunction)
Overactive immune system - hypersensitivity reactions
Autoimmune diseases - failure to recognise self
What IS HIV, what cells does it infect and what does it cause?
- retrovirus
- infects CD4 and T-cells
- causes AIDS (acquired immunodeficiency syndrome)
What are the stages of progression of HIV?
Infection
Latency
AIDS - decline in CD4 and T cells, opportunistic infections
What are the causes of secondary immunodeficiency?
Malnutrition, burns, uraemia, diabetes mellitus, immunotoxic medications, self-medication of recreational drugs/alcohol, AIDS
When is the immune system considered hyperactive?
- allergy (hypersensitivity)
- auto-immunity
- over reaction to pathogen
What is hypersensitivity?
Excessive immune reaction against harmless antigens
- type 1 (anaphylaxis, allergy) /type 4 - based on mechanism
- sensitisation = first step
Name some hyperactive conditions
Asthma, rhinitis (hay fever), peanut allergy
What is the name given to an overreaction to a pathogen?
SIRS
systematic inflammatory response syndrome
What is autoimmunity?
Failure of an organism in recognising its own constituent parts as self
Leading to an immune response against its own cells and tissues
Normally display self-tolerance –> self reactive lymphocytes (deleted centrally, suppressed in periphery)
Name some autoimmune diseases
Type 1 DM, coeliac disease, MS, Hashimoto’s thyroiditis
What type of immunity do vaccinations give?
Active immunity
Stimulates own immune system to elicit adaptive immune response to prevent future infection
What do vaccinations success depend on?
Herd immunity
What are the types of vaccination given?
- live (attenuated) vaccines (live weakened pathogen - e.g. MMR)
- inactivated vaccines (inactivated part of pathogen - e.g. Hep b)
- toxoid (bacterial toxin - e.g. Diphtheria)
- conjugated (antigen linked to protein carrier e.g. Pneumococcal)
