Week 2 – The Immune System Flashcards
Name the 2 types of immune defence system
- Innate Defence Systems (non-specific)
- And Adaptive (specific)
What 2 subsytems make up the Innate Defence system?
- Surface barriers - skin & mucosa (1st line of defence)
- Internal defences - cells & chemicals (2nd)
Adaptive is the 3rd line of immune defence and is made up of antigens. Which ones?
- Lymphocytes
- and Antigen Presenting Cells
Which can create a Humoral Immune Response
or a Cellular one - this can →
in diseases and disorders of the immune system
List 5 out of the 9 surface membrane barriers and their protective functions
- Epidermis → physical barrier to microbes
- Mucous membrane - as above but not as effective
- Mucous - traps microbes in respiratory and GI tract
- Hair - filters out microbes and dust from nose
- Cilia - together w. mucous removes microbes and dust from upper respiratory tract
- Lacrimal apparatus tears - dilute and wash away
- Saliva - washes microbes from teeth and mucous membrane of mouth
- Urine - washes microbes from the urethra
- Defecation and vomiting - expels microbes from body
Also have chemical factors eg:
Gastric juices
Vaginal secretions
Innate Defence - what is phagocytosis?
ingestion of foreign matter
Innate Defence - what do Natural Killer Cells do?
- kill infected target cells by releasing granules (cytolosis)
- or induce target cell to undergo apoptosis
- Phagocytes kill released microbes.
Innate Defence - what does Fever do?
- intensifies effects of interferons (IFNs - protect unifected host cells from viral infection
- inhibits growth of some microbes
- speeds up body reactions that aid repair
What suffix do all inflammatory conditions end with and what are the 4 signs
‘itis’
1. Red
2. Heat
3. Pain
4. Swellin
What are the body’s antimicrobial substances and what do they do?
- Interferons (IFNs) - proteins released by infected cells to help protect cells that have not yet been infected
- Iron-binding proteins - inhibit the growth of bacteria by ↓ the amount of available Fe
- Antimicrobial proteins - Complement - a major mechanism for destroying foreeign substances in the body
What is Adaptive Immunity?
ability of the body to defend itself against specific invading agents (antigens (Ag) or antibody (Ab) generators)
What 2 props distinguish the Adaptive from the Innate Immune Defence System?
- Specificity for particular Ags, and being able to distinguish self from non-self molecules
- Memory - can remember most previously encountered Ags so a 2nd encounter → more rapid & vigorous response
What are antigens (Ags) and what do they do?
- Substances that are recognised as foreign and provoke immune responses are called antigens (Ags)
- Most have epitopes that induce the production of a specific Ab or activates a T-cell
What is a Hapten?
Hapten - incomplete Ag that has reactivity but not immunogenecity
What does Antigenic determinant do?
Antigenic determinant or epitopes induce the production of a specific Ab or activates a T-cell
What is a lymphocyte and what are the two broad classes?
So a lymphocyte is a type of white blood cells which comes in 2 forms B&T cells
What are B & T Cells and what’s the difference between them?
- Adaptive immune responses are carried out by white blood cells called lymphocytes. There are two broad classes of such responses
- antibody responses - directed against extracellular pathogens, carried out by B cells
- and cell-mediated immune responses - directed against intracellular pathogens, some cancer cells and tissue transplants - carried out by T cells
- Both originate in RBM, where B cells continue to mature, but T cells mature in the Thymus
What role do antigen presenting cells play in adaptive defence?
engulf Ags, then present fragments of them on their own surface where T cells can recognise them
What are the 4 wasy to acquire Adaptive Defence systems?
- Active/ Passive
- Naturally acquired/ Artificially acquired
- active establishes immunological memory - eg vaccine
- passive does not eg IV injection of Abs
What are Immunodeficiency Diseases?
when the immune system isn’t working properly eg transplant rejection, HIV & AIDS
What are autoimmune disorders?
when T cells attack own body cells eg RA, MS
Whats the difference between humoral and cellular immunity?
- Humoral - antibody responses - directed against extracellular pathogens, carried out by B cells
- Cellular - cell-mediated immune responses - directed against intracellular pathogens, some cancer cells and tissue transplants - carried out by T cells
What roles do B, plasma and memory cells play in humoral immunity?
- Once activated a B cell undergoes clonal selection → clone of B cells consisting of plasma and memory cells
- Plasma cells secrete Abs which then travel in lymph and blood to the invasion site
- Memory cells do not secrete antibodies, but can proliferate into more memory B cells if the same antigen appeared again
What 5 things do antibodies (Abs) do?
- Neutralising antigen
- Immobilising bacteria
- Agglutinating and precipitating antigen
- Activating complement
- Enhancing phagocytosis
GAMED IgA
What are the 5 types of Antibodies (Abs) or Immunoglobulins (Igs)?
- IgG (80%) - Protects against bacteria and viruses by enhancing phagocytosis, neutralising toxins, and triggering complement system.
- IgA (10-15%) - Found in sweat, saliva, tears - Provides localised protection of mucous membranes against bacteria and viruses. Levels decrease during stress, lowering resistance to infection.
- IgM (5-10%)
- IgE (< 0.1%)
- IgD (about 0.2%)
What do T-cells do?
Most T-cells become cytoxic T-cells
In response to an AG, a cytotoxic T cell undergoes clonal selection. The result is the formation of a clone of cytotoxic T cells that consists of active cytotoxic T cells and memory cytotoxic T cells.
Active cytotoxic T cells attack other body cells that have been infected with the antigen.
Memory cytotoxic T cells do not attack infected body cells. Instead, they can quickly proliferate and differentiate into more active cytotoxic T cells and more memory cytotoxic T cells if the same antigen enters the body at a future time.
How do vaccines work?
Vaccines contain weakened or inactive parts of a particular organism (antigen) that triggers an immune response within the body
What are hypersensitivities and what are the three types?
When the immune system damages tissue as it fights off a perceived threat eg pollen that would otherwise be harmless to the body
Immediate - occur within secs and are known as allergic reaction
Sub acute - 1-3 hours
Delayed - 1-3 days
