Ch 21 - The Immune System

These flashcards cover key vocabulary and concepts related to the immune system, including definitions of terms and their roles in immunity.

What is immunity?

The body's ability to defend against unfamiliar microorganisms.

What are the two main immune system types?

• Innate Defenses

• Adaptive Defenses

Innate defenses

Nonspecific, rapid response

Adaptive defenses

Specific, slower but more effective response

What are the surface barriers of the immune system?

Skin and mucous membranes.

How does the skin prevent infections?

• Keratin

• Acid Mantle

What is the Acid mantle

Sweat and sebum create a bactericidal environment.

Keratin

Resistant to acids, bases, bacterial enzymes.

What role do mucous membranes play in defense?

• Mucus: Traps pathogens.

• Cilia: Moves mucus away from respiratory & digestive tracts

• Acid Mantle: Stomach and vaginal acidity prevent bacterial growth

What bodily fluids help eliminate pathogens?

Tears, saliva, and urine (contain lysozyme & flush bacteria)

What are Natural Killer (NK) cells?

Immune cells that target cancerous & virus-infected cells using perforin to induce apoptosis

What are the two types of phagocytes?

• Neutrophils

• Macrophages

Macrophages

A type of phagocyte that can be free (move through tissue) or fixed (reside in organs)

Neutrophils

A type of phagocyte that becomes phagocytic when encountering pathogens

What are challenges in phagocytosis?

• Some pathogens resist lysosomes

• Some bacteria have a capsule, requiring opsonins (like antibodies) for recognition.

• Large pathogens require toxic chemicals, which can damage tissue.

What are the four functions of inflammation?

• Prevents pathogen spread.

• Disposes of debris.

• Alerts the immune system.

• Initiates repair.

What chemicals trigger inflammation?

• Histamine

• Kinins

• Prostaglandins

How does prostaglandins work within an inflammation response?

Enhances inflammation & pain.

How does kinins work within an inflammation response?

Attracts WBCs, induces pain.

How does histamine work within an inflammation response?

Vasodilation, increases permeability.

What are the four steps of phagocyte mobilization?

• Leukocytosis

• Margination

• Diapedesis

• Chemotaxis

Describe Chemotaxis during phagocyte mobilization

Step 4: WBCs move toward chemicals at the injury site

Describe diapedesis during phagocyte mobilization

Step 3: WBCs squeeze through capillaries

Describe margination during phagocyte mobilization

Step 2: Phagocytes cling to capillary walls

Describe leukocytosis during phagocyte mobilization

Step 1: Release white blood cells

What are two key antimicrobial proteins?

• Interferons (IFNs)

• Complement System

Complement System

Antimicrobial plasma proteins that trigger inflammation, enhance phagocytosis, and lyse bacteria

Interferons (IFNs)

An antimicrobial protein released by virus-infected cells to warn nearby cells

What causes fever?

Pyrogens from WBCs & macrophages reset the hypothalamus.

What is the effect of a fever?

Increases metabolism and deprives bacteria of iron

How does adaptive immunity differ from innate immunity

• Specific to pathogens.

• Systemic (not localized).

• Has memory for faster secondary responses.

What are the two types of adaptive immunity?

• Humoral Immunity

• Cellular Immunity

Cellular Immunity

T cells that directly kill pathogens

Humoral Immunity

B cells and antibodies

What are the two types of antigens?

• Complete Antigens

• Haptens (Incomplete Antigens)

Haptens (Incomplete Antigens)

Must bind to a protein carrier to be recognized

Complete antigens

Trigger immune responses

What are self-antigens?

MHC Proteins help the body distinguish between self and non-self

What are the three main adaptive immune cells?

• B Cells: Humoral immunity.

• T Cells: Cellular immunity.

• APCs: Present antigens to activate T cells.

What are the three types of antigen-presenting cells (APCs)?

• Dendritic cells

• Macrophages

• B cells

B cells

Antigen-presenting cells (APCs) that present antigens to helper T cells

Macrophages

Antigen-presenting cells (APCs) that activate T cells

Dendritic cells

Antigen-presenting cells (APCs) that transport antigens to lymph nodes

What happens in primary responses?

B cells activate, produce plasma cells & antibodies.

What happens in secondary responses?

Memory B cells rapidly produce antibodies upon re-exposure.

What are the types of humoral immunity?

• Active Immunity (body makes antibodies)

• Passive Immunity (antibodies received)

What are two mechanisms of Active Immunity?

• Natural (Infection.)

• Artificial (Vaccine)

What are two mechanisms of Passive Immunity?

• Natural: From mother.

• Artificial: Injection of antibodies.

What are the five classes of antibodies?

• IgG

• IgA

• IgM

• IgE

• IgD

What is an IgM antibody?

First responder; largest antibody

What is an IgA antibody?

Found in secretions

What is an IgD antibody?

B Cell receptor

What is an IgG antibody?

Most abundant antibody; important for primary and secondary response

What is an IgE antibody?

Triggers allergic reactions with histamine

What are the four mechanisms of antibody action?

• neutralization

• agglutination

• precipitation

• complete activation

What is neutralization?

Blocks pathogen binding sites; mechanism of antibody action

What is agglutination?

Clumps antigens for easier phagocytosis; mechanism of antibody action

What is precipitation?

Makes soluble antigens insoluble; mechanism of antibody action

What is complete activation?

Triggers cell lysis and inflammation; mechanism of antibody action

What are the three types of T cells?

Cytotoxic T cells (T_C), Helper T cells (T_H), Regulatory T cells (T_REG)

What are Helper T cells (T_H)?

Activate B cells and cytotoxic T cells.

What are Cytotoxic T cells (T_C)?

Destroy infected and cancerous cells using perforin and granzyme.

What are Regulatory T cells (T_REG)?

Suppress immune responses to prevent autoimmunity.

What are immunodeficiencies?

Conditions that impair immune function.

What are examples of immunodeficiencies?

• SCID: Genetic, no lymphocytes.

• AIDS: HIV attacks Helper T cells.

What happens in autoimmune diseases?

The immune system attacks "self" tissues.

What are examples of autoimmune diseases?

• Rheumatoid arthritis (joints).

• Multiple sclerosis (CNS).

• Type 1 diabetes (pancreas).

• Graves' disease (thyroid).

How are autoimmune diseases treated?

Immunosuppressive drugs (increase infection risk).