Immune System Basics Quiz

Immune System Basics

• Main function is to protect the body from harmful pathogens, which may be internal or external.
• Pathogens include bacteria, viruses, fungi, and protozoans.

Lines of Defense

• The immune system has three lines of defense:
  • First Line of Defense: Physical and chemical barriers such as skin and mucous membranes.
  • Second Line of Defense: Non-specific immune responses such as inflammatory responses and phagocytosis.
  • Third Line of Defense: Specific immune response targeting specific pathogens.

First Line of Defense Components

• Skin: Acts as a mechanical barrier to prevent pathogen entry.
• Mucus: Chemical barrier with enzymes that destroy pathogens; found in saliva and tears.
• Gastric Juice: Acidic fluid that kills many microbes in the stomach.
• Bacteria: Natural flora that competes for space and resources, inhibiting harmful pathogen growth.

Second Line of Defense Mechanisms

• Inflammatory response triggers chemical alarms (e.g., histamines) that signal other defense mechanisms.
• Phagocytosis: Process where leukocytes (white blood cells) engulf and break down pathogens.
• Involves complement proteins, natural killer cells, and interferons for pathogen attack.

Defense Types

• Nonspecific Defenses: Present in the first and second lines of defense, attacking invaders indiscriminately.
• Specific Defenses: Occur in the third line of defense, targeting specific antigens.

Antigens and Immune Responses

• Antigens are molecules recognized as foreign by the immune system, such as bacterial proteins and toxin substances.
• Immune responses are categorized into two types:
  • Humoral Response: Involves B cells and antibody production.
  • Cell-Mediated Response: Primarily involves T cells targeting infected host cells.

Lymphatic System

• Comprises organs and tissues like lymph nodes, bone marrow, spleen, and thymus that produce and store immune cells.

Key Lymphocytes

• B Cells: Combat infections by producing antibodies; activated by helper T cells.
• T Cells: Destroy virus-infected cells; includes:
  • Cytotoxic T Cells: Attack infected cells with toxins.
  • Regulatory T Cells: Regulate immune responses to prevent autoimmunity.

Memory Cells

• Some plasma cells become memory cells, enabling a faster immune response during subsequent infections.

Immunity Types

• Active Immunity: Developed after fighting an infection; involves the production of memory cells through exposure to pathogens or vaccination.
• Passive Immunity: Transfer of antibodies from one individual to another without direct exposure to the pathogen; for example, maternal antibodies to a fetus.

Immunization

• A method to develop active immunity by exposing the body to a weaker version of a pathogen to stimulate an immune response.

Test your knowledge on the immune system's structure and functions, including its lines of defense against harmful pathogens. This quiz covers the first and second lines of defense, detailing components such as skin, mucus, and inflammatory responses.