- Intracellular pathogens - Help B cell make antibodies - Activate macrophages and NKCs (natural killer) - Help development of CD8

Immunology Flashcards by Louise Smith-Litière

Lifespan of neutrophils

12 days

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Lifespan of monocyte

Months

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Lifespan of macrophages

Months/years

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Basic role of neutrophils

Phagocytosis (innate immunity)

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Basic role of monocytes

Phagocytosis (innate), Antigen presentation (adaptive)

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Basic role of macrophages

Phagocytosis (innate), antigen presentation to T cells (adaptive), remove foreign and dead material

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Process of phagocytosis

Chemotaxis and adherence to pathogen (opsonins)
Ingestion by pseudopodia wrapping round pathogen and engulfing
Formation of phagosome, fusion with lysosome -> phagolysosome
Formation of residual body containing indigestible material
Excretion of waste via exocytosis
MHC class II formed and present on the surface of APC

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Lifespan of eosinophils

8-12 days

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Eosinophils present in what type of pathology

Parasitic infections and allergic reactions

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Lifespan of basophils

2 days

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Where are basophils found

Blood

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Where are mast cells found

Tissue only

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What substances do mast cells release

Cytokines, histamine, heparin

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T lymphocyte functions

Recognise antigen displayed by APC
Produce cytokines
Activate B cells
Cell mediated immunity

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4 main types of T cell

T helper cell/ CD4
Cytotoxic T cell/ CD8
T memory cell
T regulatory cell

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T helper cell 1

Intracellular pathogens
Help B cell make antibodies
Activate macrophages and NKCs (natural killer)
Help development of CD8

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T helper cell 2

Same as T helper cell 1 except extracellular pathogens

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Where are T lymphocytes found

Blood, lymph nodes, spleen

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Lifespan of B lymphocytes

Years

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Functions of B lymphocytes

Recognise antigens displayed by APC
Express antibodies on cells surface
Plasma cells make antibodies

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Natural killer cells

Type of lymphocyte that recognises infected cells (viral and tumour) and kills them via apoptosis

Dendritic cell function

APC
Induce primary immune response in inactive lymphocytes
Produce cytokines and other factors that promote B cell activation and differentiation

Main purpose of complement system

Remove + destroy antigens through opsonisation and direct lysis

Pathways of the complement system

Classical - activated by antibody-antigen complex
Alternative - activated by foreign surface antigens
Lectin - mannose-binding lectin-mannose residues on surface of pathogen

Once activated what does complement do

- Lyse microbes directly - Increase chemotaxis - Enhance inflammation - Induce opsonisation

Opsonisation

The process by which an antigen becomes coated with substances that make it easier to engulf in phagocytosis

Antibodies

Protein produced in response to an antigen. Highly specific

Antigen

Molecule on the cell surface that identifies foreign substances as foreign

Epitope

Part of antigen that binds to the antibody/receptor binding site

Affinity

Measure of binding strength between epitope and antibody

Basic structure of an antibody

- 2 light chains and 2 heavy chains - Variable region (FAB) which binds to epitope - Constant region that binds to immune cells - Disulfide bridges between chains

5 classes of immunoglobulin

IgA, IgE, IgG, IgM, IgD

IgG

70-75% Important to secondary immune response Crosses the placenta to give passive immunity to foetus

IgA

15% | Predominant Ig in saliva, colostrum, bronchiolar and genitourinary secretions

IgM

10% Found in blood Intravascular neutralisation of organisms

IgE

Basophils and mast cells express IgE specific receptor | Antigen binds -> basophils and mast cells release histamine

IgD

Expressed on naive B cells and acts as B cell antigen receptor

Which antibodies neutralise toxins

IgG, IgA

Which antibodies immobilise motile microbes

IgM

Which antibodies bind to phagocytes

IgG, IgA - enhance phagocytosis

Which antibodies bind to mast cells

IgE -> histamine release

Which antibodies bind to natural killer cells

IgG -> enhanced killing of infected cells

Cytokines

Soluble proteins secreted by lymphocytes or macrophages/monocytes that act as stimulatory or inhibitory signals between cells

Interleukins

Cytokines that act between cells of the immune system. Cause cells to divide/differentiate/secrete factors. Can pro or anti-inflammatory

Chemokines

Cytokines that induce chemotaxis of leukocytes

Interferons

Induce a state of antiviral resistance in uninfected cells and limit the spread of viral infection

Colony stimulating factor

Stimulate direct differentiation of bone marrow stem cells

Tumour necrosis factor

Mediate inflammation and cytotoxic reactions

Characteristics of innate immunity

- Present at birth - Non-specific - Rapid response - Phagocytes and natural T killer cells

1st line of defence

- Barrier to antigen - Slow response - Effective but limited