D3.3 - The Lymphatic System and Immunity

Lymphatic System and Immunity

• The lymphatic system works with the circulatory system to protect the body from infection
• The blood, specifically white blood cells, also plays an important role in immunity
• The lymphatic system is a network of vessels, glands, and nodes spread throughout the body
• Lymph fluid, similar to blood plasma, is collected by the lymphatic system
• Lymph helps maintain fluid balance in the body by bathing cells, mixing with general blood circulation.

Human Defense System

• The first line of defense is to prevent organisms from entering the body
• Skin and mucus lining respiratory passages prevent most microbes
• Stomach acids, oils in skin, and enzymes in tears break down bacteria

Important Terms

• Antigen: A protein that stimulates antibody formation
• Antibody: A protein in blood that reacts with an antigen
• Pathogen: An organism that causes disease in a host

The Lymphatic System and Immunity

• Lymph nodes are where white blood cells mature
• Lymph nodes also contain macrophages (white blood cells that trap and destroy bacteria)
• Infections can lead to an increase in macrophages, causing lymph glands to swell.

Immunity (First Line of Defense)

• Physical and chemical barriers of the body, including skin, stomach acid, eyelashes, tears, and cilia, protect from foreign invaders.

Immunity (Second Line of Defense)

• Involves non-specific white blood cells called phagocytes, that engulf and destroy foreign pathogens in the bloodstream
• Also referred to as the inflammatory response, often resulting in swelling and fever
• Three types of phagocytes: monocytes, macrophages, and neutrophils
• Phagocytes destroy harmful pathogens through phagocytosis, a process of engulfment.

Immunity (Third Line of Defense)

• Also known as antibody-mediated immunity
• Lymphocytes (specific white blood cells) target pathogens based on specific markers
• B-cells and T-cells are types of lymphocytes
• Antibodies, a type of protein, are produced to help destroy pathogens.

T-Cells

• Helper T-cells analyze pathogens after phagocytosis and recruit B-cells.
• Killer T-cells destroy virus-infected and cancerous cells.
• Suppressor T-cells monitor killer T-cells, preventing them from harming healthy tissues.

B-Cells

• B-cells are recruited to the site of phagocytosis by T-cells
• B-cells divide into memory B-cells and plasma cells
• Memory B-cells display antibodies to quickly identify pathogens
• Plasma cells produce large amounts of antibodies to target specific pathogens.

Specific Defenses (Antibody-Mediated Immunity)

• The third line of defense is antibody-mediated immunity
• Antibodies recognize foreign substances and either neutralize or destroy them
• Lymphocytes are responsible for this immune response
• The body distinguishes "self" from "non-self" proteins and molecules

The Immune Response

• Phagocytes present pathogen antigens to helper T-cells
• Helper T-cells activate B-cells, producing antibodies
• Killer T-cells destroy infected or cancerous cells
• Suppressor T-cells regulate the immune response

Antibodies

• Antibodies are proteins in the bloodstream that recognize antigens
• They trigger a series of events to neutralize or destroy pathogens
• Antibodies are specific to different pathogens and are generated after their destruction by white blood cells

Blood Types

• Blood transfusion involves transferring blood from one person to another
• Different blood groups exist due to different red blood cell antigens
• The ABO system determines blood type based on A, B antigens
• Agglutination is the clumping of red blood cells due to incompatible blood types.

Blood Groups - How They Work

• Blood types are based on antigens and antibodies
• Blood type A has A antigens and B antibodies
• Blood type B has B antigens and A antibodies
• Blood type AB has both A and B antigens and neither A nor B antibodies
• Blood type O has neither A nor B antigens and both A and B antibodies

Rhesus (Rh) Factor

• Rh factor is a second antigen found on red blood cells
• People can be either Rh+ or Rh-
• Rh- individuals produce antibodies when exposed to Rh+ blood during transfusions or pregnancy causing problems for Rh+ fetuses during subsequent pregnancies.

Rhesus Factor and Pregnancy

• If a Rh- mother carries an Rh+ fetus, antibodies might be produced against the fetal blood cells
• This can cause problems for the fetus
• Treatment for this issue often involves a blood transfusion for the child.

Allergies

• Allergies occur when the immune system mistakenly recognizes harmless foreign particles as threats
• This causes an immune response leading to sneezing, runny nose, watery eyes.
• Antihistamines can alleviate these symptoms by blocking histamine effects.

Acquired Immune Deficiency Syndrome (AIDS)

• AIDS is caused by the Human Immunodeficiency Virus (HIV)
• HIV is transmitted through bodily fluids like blood or through unprotected sex
• HIV specifically targets and kills T-cells, crippling the immune system
• The virus itself doesn't immediately kill but prevents the immune system from functioning effectively.

Test your knowledge on the lymphatic system and its role in immunity. This quiz covers key concepts, definitions, and functions of the human defense system. Learn about how the body protects itself from infections through the collaboration of the lymphatic and circulatory systems.