NURS524 2401: Immune and Lymphatic Systems

Lymph is a fluid that forms in the interstitial space and enters the lymphatic vessels
Approximately 3L of fluid enters the lymphatic vessels every day
Lymph has a similar composition to plasma
Lymph is prevented from flowing backwards by valves and lymph nodes

Lymphatic vessels become smaller as they move towards the heart
Lymphatic vessels are prevented from flowing backwards by valves
The distribution of lymphatic vessels and drainage of lymph is asymmetrical
The right upper torso, arm, and right side of the head drain into the right lymphatic duct

Lymphoid organs include the spleen, tonsils, Peyer's patches, thymus gland, and appendix
The spleen is located in the upper left abdominal quadrant, posterior to the stomach
The thymus gland is located in the superior mediastinum, posterior to the sternum
Lymphoid organs are responsible for the production and maturation of immune cells

The immune system has innate and adaptive defences
Innate defences are non-specific and provide immediate protection against infection
Adaptive defences are specific and provide long-term immunity against infection
The immune system has three lines of defence against infection: skin and mucous membranes, phagocytes and natural killer cells, and B and T lymphocytes

The skin and mucous membranes provide a physical barrier against infection
The skin and mucous membranes also produce antimicrobial proteins and acids that inhibit the growth of microorganisms
Sweat and tears also contain antimicrobial proteins and acids
The skin and mucous membranes are the first line of defence against infection

Phagocytes and natural killer cells provide the second line of defence against infection
Phagocytes engulf and digest pathogenic microorganisms using acids and enzymes
Natural killer cells release proteins that create holes in the target cell membrane
Phagocytes and natural killer cells work together to eliminate pathogenic microorganisms from the body

The third line of defence against infection is adaptive and specific
The third line of defence involves the activation of B and T lymphocytes
B lymphocytes produce antibodies, which bind to antigens, marking them for destruction
T lymphocytes directly attack and destroy infected cells
The third line of defence provides long-term immunity against infection### Antibodies and Antigens
Antibodies bind to specific antigens.
Antibodies are Y-shaped proteins produced by plasma cells.
Antibodies are found in the blood plasma and other body fluids.
Antigens are substances (often proteins) that stimulate an immune response.
Antigens are the part/s of a pathogen recognised by the immune system.

Plasma cells produce antibodies.
Plasma cells are responsible for producing a large amount of antibodies during an immune response.

The primary immune response is slower and produces fewer antibodies.
The secondary immune response is faster and produces more antibodies and memory B cells.
The secondary immune response is to the same antigen as the primary response.

Agglutination: Antibodies help to clump together antigens, making it easier for other immune cells to remove them.
Neutralisation: Antibodies bind to antigens, preventing them from entering host cells.
Phagocytosis: Antibodies mark antigens for destruction by other immune cells.
Precipitation: Antibodies bind to antigens, causing them to precipitate out of solution.

Active immunity is developed when an individual is vaccinated against a disease or infected with a pathogen.
Passive immunity is developed when an individual receives antibodies or immune cells from another source.
Active artificially acquired immunity is developed when an individual is vaccinated against a disease.
Natural immunity is developed when an individual is infected with a pathogen.

Cytotoxic T cells: directly kill infected cells.
Helper T cells: assist in the activation of other immune cells.
Macrophage/APC: present antigens to T cells.
Memory T cells: remember specific antigens and respond quickly to future infections.
Regulatory T cells: regulate the immune response to prevent overactivation.

Cytokines: chemical messengers that activate the immune system.
B lymphocytes: produce antibodies and respond to antigens.
T lymphocytes: directly kill infected cells or assist in the activation of other immune cells.
Memory cells: remember specific antigens and respond quickly to future infections.
Plasma cells: produce large amounts of antibodies during an immune response.
Cytotoxic T cells: directly kill infected cells.
Helper T lymphocytes: assist in the activation of other immune cells.
Antibodies: bind to specific antigens and mark them for destruction.
Natural killer cells: directly kill infected cells and tumour cells.
Macrophages: present antigens to T cells and engulf foreign particles.
Neutrophils: engulf foreign particles and bacteria.