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Flashcards in |mmunity Deck (21):

What are the physical barriers in innate immunity?

Respiratory tract: mucus and ciliated epithelium
Eyes: tears, lysozyme/lactoferrin
Skin: sweat, antimicrobials, low pH commensal bacteria, skin shredding
GI tract: stomach acidity, intestinal pH, normal flora, mechanical flushing
Genitourinary tract: washing by urine, vaginal secretions, urine acidity, lysozyme


What are the immune tissues?

Bone marrow
Tonsils and adenoids
Lymph nodes
Peyer's patches


Cytokines (interferon) importance in innate immunity

Cell infected with virus produces IFN
IFN acting internally protects infected cell
Secreted IFN binds to receptors on nearby cells and triggers anti-viral response


Natural Killer cells in innate immunity

White blood cells:
- able to recognise and kill infected cells
- NK cell remains unharmed


Phagocytes in innate immunity

Ingest and kill microbes
1. Phagocyte attaches to microbe by non-specific receptors
2. Phagosome is formed
3. Lysosome fuses with phagosome, damages and destroys microbe
4. Release of microbial agents


Polymorphonuclear cells Importance in innate immunity

70% neutrophils
- first to arrive at site of infection
- non-dividing, short lived (1 day)
- granulated = chemical attack


Signs of inflammation

Erythema (redness)
Possible loss of function
Widespread systemic inflammation may lead to septic shock & death.


Inflammation in innate immunity

- vasodilation and increased permeability
- accumulation of blood
- leakage of clotting factors
- chemotaxis of neutrophils/ macrophages
- death of phagocytes
- initiation of tissue repair


Fever in innate immunity

High temperate triggered by resetting hypothalamic thermostat
- triggered by cytokines/toxins
- inhibits bacterial growth
- speeds up some enzyme reactions aiding tissue repair


Adaptive immunity

A dedicated system of tissues, cells and molecules that act
in concert to provide specific immune responses:
> memory
> specificity
LYMPHOCYTES = cells of adaptive immunity response
clonal selection and memory
B cells and antibody-mediated immunity
T cells and cell-mediated immunity


Describe the adaptive defence system

Two types of lymphocytes:
- B lymphocytes (B cells)
- T lymphocytes ( T cells)
Cells recognise pathogens using cell-surface receptors
Each has a unique binding site for a different epitope
Only those lymphocytes that are specific for components of infecting pathogen are selected
→ divide, proliferate & differentiate into effector lymphocytes
→ some proliferate into memory lymphocytes


Describe T lymphocytes

Kill virus-infected cells (cytotoxic T cells)
Activate macrophages
Help antibody responses ( T helper cells)
Immunoregulatory function


What are the two types of T cells?

CD8 or CD4 glycoprotein markers
- both have T cell receptors that recognise antigens
- T cell receptors recognise peptide antigens presented on surface of innate immune system cells eg. macrophages
- antigen needs to be presented bound to MHC molecules: 2 classes
> MHC class 1 - on all cells with a nucleus ( not RBC)
> MHC class 11 - on professional antigen presenting cells (APCs)
MHC1 present antigens of intracellular origin eg. viral proteins to CD8 cells = cytotoxic T cells
MHC11 present antigens of extracellular origin eg. from bacteria to CD4 T cells = differentiate into T helper cells:
- activate macrophages
- help B cells become antibody producing plasma cells


What is SCID?

Affects lymphocytes
- failure to thrive
- viral gastroenteritis
- viral chest infection
- parasitic chest infection
- bacterial septicaemia
- fungal urinary infection


What is DiGeorge syndrome

- decreased or absent T cell numbers and function
- variable antibody function:
> IgM normal to low
> IgG low to absent
- increase susceptibility to vial, fungal infections


HIV and immunity

Mature T lymphocytes depleted


B lymphocytes

Can differentiate into memory B cells and plasma B cells that can produce antibodies


Main classes of antibodies

IgG = blood and tissue antibody, binds phagocytes, neutralised toxins
IgM = blood antibody, acts as a B cell receptor, first antibody produced in infection
IgA = secretory antibody, protection of mucosal surfaces
IgE = binds to mast cells and basophils, important in parasite infections
IgD = membrane receptor


How do antibodies protect from infection?

Block binding of pathogens and toxins
Facilitate phagocytosis by eg macrophages/neutrophils
Kill bacteria by activating complement


Contribution of antibody to host resistance

Neutralisation of toxins
Extracellular lysis of bacteria (with complement)
Facilitates internalisation for intracellular killing by phagocytes neutrophils and macrophages)
Expulsion of parasites via inflammatory reactions
Passive immunity by transplacental transfer


Bruton's disease

Failure of B-lymphocyte precursors to mature into B lymphocytes and plasma cells
- can't clear pyrogenic bacteria eg. Staphylococci
- recurrent respiratory/middle ear infections