Immunology

LO's
•Describe the general components of the lymphatic system and list its functions
•Describe the formation and flow of lymph
•List and describe the primary and secondary lymphatic organs of the body
•Describe the development of the lymphatic system
•Discuss the roles of the skin and mucous membranes, antimicrobial substances, phagocytosis, inflammation, and fever in nonspecific resistance to disease
•Define immunity and describe how T cells and B cells arise
•Explain the relationship between an antigen and an antibody
•Describe the roles of antigen presenting cells, T cells, and B cells in cell-mediated and antibody-mediated immunity
•Explain how self-tolerance occurs

the four types of pathogens are- fungi, bacteria, parasites and virus

The immune system

consists of four organs:

1)Bone marrow- origin of all immune response cells

2)Thymus- cells are matured and tested here

3)Spleen- an immunologic filter which stores cells

4)Lymph nodes and tissue- filters and storage points

The immune system consists of cells and organs working together to protect the body against pathogen invasion.

Innate immunity

-non-specific

-uses pre-formed components

-has no memory

-present at birth

Acquired immunity

-very specific 

-can respond to wide variety of threats

-has memory so provides an enhanced response to subsequent exposures

-can activate components of the innate response, leading to enhanced response

-involves specific T-cells, B-cells, and antigen presenting cells and cytokines

The non specific/innate immune system

-this is the body's first line of defence including;
Forms of protection:
-skin
-mucous
-cilia
-acid secretion
-tears
-earwax
-enzymes
-inflammation-increases: blood flow, temp, and white blood cells
-expulsive reflexes eg vomiting, coughing, sneezing
-non specific responses: inflammation and fever
-specific response: antibodies and activated cells

The second line of defence consists of;
-imflammatory response
-wbc produced
-fever
-interferon (resist viral infection, secreted by infected cells to protect other cells from infection)

The complement system

-part of the non-specific immune response

-a series of at least 20 glycoproteins are activated in a cascade

-there are no cells in this system but during infection molecules are activated, leading to a sequence of events on the surface of pathogen that helps destroy infection

-activated by proteins present on surface of pathogen or by action of antibodies on infecting agent

Inflammation

-caused by endogenous (bacterial toxins/cell walls) and exogenous stimuli (in plasma or produced by cells)

-occurs in response to tissue injuries by pathogens and as a result of physical trauma, intense hear, irritating chemicals and in allergic reactions

-injured cells are destroyed, diluted, or walled off

-can be harmful

-organism cannot survive without it

-if the offending stimulus cannot be removed rapidly then the inflammation can become chronic

///Functions of inflammation;

-prevents spread of damaging agents to nearby tissues

-aids disposal of cell debris and pathogens 

-sets stage for repair process

Five signs of inflammation

1) Calor- heat

2) Rubor- redness

3) Tumor -swelling

4) Dolor -pain

5) Functio laesa- loss of impairment of function

-Acute inflammation: short duration, protein-rich exudate, healthy

-This will lead to vascular permeability:

•Contraction of epithelial cells of venules (actin present)

•(Direct damage to cells and leakage)

•Protein-rich exudate leaves vessels or interstitial spaces

•Water follows

•Hence swelling

•(Lymphatic drainage occurs to lymph nodes)

-Chronic inflammation: unhealthy, non-homeostatic

Cellular changes after inflammation:

•Decreased axial streaming

•Margination

•Pavementing and adhesion

•Emigration

•Chemotaxis (cells recruited to area, especially neutrophils and monocytes-macrophages)

Inflammation after injury:

1. Mast cell degranulation –mast cells releases serotonin and histamine into the surrounding tissues. These work with the other two processes below to provide the complete inflammatory signs and symptoms.

2. The activation of four plasma protein systems which work together to activate and assist the inflammatory and immune processes

 a. complement (helps to orchestrate the inflammatory response)

 b. clotting (stops bleeding and repairs damage)

 c. kinin (involved in vascular permeability)

 d. immunoglobulins (destroys bacteria)

3. The movement of phagocytic cells to the area in order to phagocytose bacteria or any other non-self debris in the wound.

SUMMARY OF INFLAMMATION:

The timetable of a typical inflammatory response to tissue injury is:

• Arterioles near the injury site constrict briefly.

• Vasoconstriction is followed by dilation and increased blood flow(redness and heat).

• Dilation of arterioles increases pressure, causing exudation of plasma proteins and blood cells into surrounding tissues. causes oedema (swelling).

• Nerve endings stimulated, partly by pressure (pain).

• The clotting and kinin systems, along with platelets block any tissue damage by commencing the clotting process (clot formation).

• White blood cells – phagocytes and lymphocytes migrate and destroy any pathogens.

• They also remove the debris (exudates and dead cells in the form of pus) which results from the war against the foreign invader. (cellular infiltration).

• These systems/blood cells/tissue cells will remain in the area until tissue regeneration takes place. This is known as resolution.

The specific response/ acquired/adaptive immunity

-the immune system amplifies the inflammatory response
-the immune system recognises specific foreign substances and responds by destroying or neutralising them
-this means the immune system must have encountered the substances previously to have recognised them

The lymphatic system

consists of:

-tonsils anf adenoids

-thymus gland

-lymph nodes

-spleen

-appendix

-patches of lymphoid tissue in the intestinal tract

-the lymph is pushed around the body by contractions. of smooth muscular walls of the lymph vessels and the flexing and relaxing of striated muscle in the body due to movement.

Lymphatic system 3 functions- drainage, immune response, and absorbs fat from gut

Specific response
-Amplification of the inflammatory response:
-increased blood(vasodilation)-slows blood flow
-redness
-increased permeability
-increased pain
-swelling
-increased temperature

CELLS OF THE IMMUNE SYSTEM:

•T Cells; T Helper cells which initiate and co-ordinate the response and T Killer cells which attack and destroy pathogens

–B Cells; which produce antibodies against pathogens. Antibodies are specialised proteins which coat pathogens and identify them to other cells for their removal

–Natural Killer Cells; like the T Killer cells these attack pathogens directly and tend to be more aggressive

–Granulocytes; either neutrophils, basophils oreosinophils which engulf pathogens

–Macrophages; engulf all foreign protein and waste, also help educate the immune response cells

-NEUTROPHILS- lobed nucleus, short-lived, phagocytose bacteria. Majority of wbc

-EOSINOPHILS- defence against parasites, increases in allergies

-BASOPHILS- release substances involved in inflammation eg mast cells

-MONOCYTES- precursor of macrophages

-CYTOKINES- communication molecule

-ANTIBODY- see cgp textbook for structure and function

❖There are 5 classes of antibodies:

•IgG – a monomer with two antigen-binding sites

❑Comprises 80% of total antibody

❑Only class able to cross the placenta

❑Provides long-term immunity

•IgM – a pentamer with ten antigen-binding sites

❑It is a great activator of complement, but has a short-lived response.

❑It is the first antibody to appear in an immune response

•IgA – a dimer with four antigen-binding sites

❑prevalent in body secretions like sweat, tears, saliva, breast milk and gastrointestinal fluids

•IgE – a monomer involved in allergic reactions

❑comprises less than 0.1% of total antibody in the blood

•IgD – a monomer with a wide array of functions, some of which have been a puzzle since its discovery in 1964

Phagocytosis