The Immune System: Defense Mechanisms and Immunity

First Line of Defense

Prevents pathogen entry through structural barriers.

Skin

Acts as a barrier with salt and acids.

Mucus Membranes

Secretes mucus, enzymes, and cilia for protection.

Tears

Contain enzymes that help eliminate pathogens.

Digestive Juices

Acids and enzymes that destroy ingested pathogens.

Second Line of Defense

Involves cellular activity to attack pathogens.

White Blood Cells (WBCs)

Engulf and consume foreign invaders like pathogens.

Macrophages

Type of WBC that engulfs and digests pathogens.

Pus

Composed of dead pathogens and WBCs in infection.

Lymphatic System

Filters materials in lymph nodes before blood circulation.

Third Line of Defense

Involves immune response and antibody production.

Antibody

Specific protein produced to destroy antigens.

Antigen

Foreign protein that triggers an immune response.

Neutralization

Blocks virus attachment to host cells.

Clumping

Pathogens aggregate for easier engulfment by macrophages.

Attachment of Antibody

Causes foreign cells to burst open.

Inherited Immunity

Present at birth, no prior exposure needed.

Acquired Immunity

Developed through exposure to pathogens or vaccines.

Active Immunity

Host produces antibodies after exposure to antigens.

Naturally Acquired Active Immunity

Antibodies from recovering from an illness.

Artificially Acquired Active Immunity

Antibodies from vaccination with weakened pathogens.

Passive Immunity

Antibodies transferred from another host.

Naturally Acquired Passive Immunity

Antibodies from mother to child via milk.

Artificially Acquired Passive Immunity

Injection of antibodies from another host.

Fever

Increased body temperature to fight infections.

Antibiotics

Substances that inhibit or kill microorganisms.

Disinfectant

Kills pathogens on contact, not for living tissue.

Antiseptic

Slows pathogen growth, safe for human skin.

Immune Response Steps

Recognition, amplification, attack, and slowdown of pathogens.