By Isabella de Jesus, Sarah Dillon, and Moriah Becker

Nonspecific Defenses Against Infection First line of defense- skin; physical barrier against pathogens Mucous, saliva, and tears contain lysozyme that breaks down bacterial cell walls Second line of defense- Inflammatory response: begins when pathogen stimulate cells called mast cells to release chemicals known as histamines white blood cells move from blood vessels to infected tissues and engulf and destroy bacteria Interferon: interfere with viral growth by slowing down the production of new viruses Fever: releases chemicals that increase body temperature which slows down or stops the growth of some pathogens

Specific Defenses Against infection Third line of defense- Immune system: inactivates or kills any foreign substances or cells that enter the body Respond to a particular pathogen Specific immune defenses are triggered by molecules called antigens

Two Types of Immunity Humoral immunity- Depends on the action of antibodies that circulate in the blood and lymph Plasma cells produce and release antibodies that are carried through the bloodstream Memory B cells react quickly if the same pathogen enters the body again Cell- mediated immunity- Depends on the action of macrophages and several types of T cells Defends the body against some viruses, fungi, and single celled pathogens T cells also protect the body from cells that become cancerous

Acquired immunity Active immunity- Vaccination that stimulates the immune system with an antigen The immune system produces memory B cells and memory T cells that quicken and strengthen the body’s response to a repeated infection Passive immunity- Antibodies produced against a pathogen by other individuals or animals to produce temporary immunity Lasts only a short time because the immune system eventually destroys the foreign antibodies

Vaccination Injection of weakened or similar but less dangerous pathogen to produce immunity

Immune System Disorders Allergies- antigens that cause allergic reactions are called allergens They trigger inflammatory response by causing mast cells to release histamines May cause sneezing, watery eyes, and runny nose, etc. Asthma- A chronic disease caused by allergic reactions in the respiratory system Causes air passages to narrow causing wheezing and coughing and difficulty breathing

HIV and AIDS Human Immunodeficiency Virus- Causes AIDS Deadly because it can hide from defenses of the immune system and attacks key cells in the immune system leaving it weak AIDS- No cure for AIDS HIV mutates and evolves rapidly

Key Vocabulary Vector- animal that transports a pathogen to a human Inflammatory response- nonspecific defense reaction to tissue damage caused by injury or infection Histamines- chemical released by mast cells that increases the flow of blood and fluids to the infected area during an inflammatory response Fever- increase body temperature that occurs in response to infection Pathogen- disease causing agent Interferon- group of proteins that help cells resist viral infection Immune response- the body’s specific recognition response in memory to a pathogen attack Antigen- any substance that triggers an immune response Antibody- protein that either attacks antigens directly or produces antigen binding proteins Active immunity- immunity the develops as a result of natural or deliberate exposure to an antigen Passive immunity- temporary immunity that develops as a result of natural or deliberate exposure to an antibody