NURS524 2401: Immune and Lymphatic Systems

Immune and Lymphatic Systems

Lymph

• 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

• 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

• 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

Immune System Introduction

• 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

First Line of Defence

• 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

Second Line of Defence

• 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

Third Line of Defence

• 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 and Antibody Production

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

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.

Mechanisms of Antibody Protection

• 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.

Immunity

• 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.

Cell-Mediated Immunity

• 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.

Immune Functions

• 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.