Exam 4 Microbiology

Innate (Nonspecific) Host Defenses

Chapter 17

Parenteral immunity

Entry into the body through breaks in the skin (e.g., injections, wounds).

Define immunity.

Ability to resist infection or disease.

What does susceptibility refer to?

Likelihood of getting a disease.

Innate immunity

Non-specific defenses present at birth.

Adaptive immunity

Specific defenses developed after exposure to pathogens.

Nonspecific defenses

Defenses that protect against all pathogens, not targeted.

What constitutes the first line of defense in the immune system?

Physical and chemical barriers that block pathogens.

Physical Defenses

First line defense - Skin and mucous membranes that block pathogens.

Epidermis

Outer skin that prevents pathogen entry - physical defense

Muscos Membranes

Line body cavities; trap microbes - physical defense

Mucociliary escalator

Cilia move mucus (and trapped pathogens) out of the lungs. -physical defense

Antimicrobial peptides

Chemical Defenses- small proteins that kill microbes.

Plasma

Chemical defense- The liquid portion of blood containing proteins.

Cytokines

Cell signaling proteins involved in immune responses.

Autocrine

Cell signals itself

paracrine

signals nearby cells

endocrine

Signals distant cells via bloodstream

Erythrocytes

Red blood cells; carry oxygen.

Platelets

Help with blood clotting.

Leukocytes

White blood cells; immune cells that fight infection.

Define hematopoiesis.

The formation of blood cells.

Granulocytes

WBCs with granules, such as neutrophils.

Phagocytosis

Cells that engulf pathogens.

Macrophages

Large phagocytes that digest pathogens.

Dendritic cells

Present antigens to activate adaptive immunity.

PAMPs

Pathogen-Associated Molecular Patterns; molecules recognized as foreign.

Diapedesis.

WBCs exiting the bloodstream to enter tissues.

Phagolysosome

A vesicle where pathogens are destroyed.

Complement system

Proteins that enhance immune responses.

MAC

Membrane Attack Complex: Punctures pathogen membranes.

Interferons

Proteins that block viral replication.

histamine

Causes inflammation and increases blood flow.

Inflammation

Local response causing redness, swelling, and heat.

Fever

Elevated body temperature to fight infection.

Pyrogens

Substances that cause fever

First Line of Defense

Physical & chemical barriers (skin, mucus, fluids)

Second Line of Defense

Phagocytosis, inflammation, fever

Neutrophils

First responders; engulf pathogens

Adaptive (Specific) Host Defenses

Chapter 18

Adaptive Immunity

Specific, targeted immune response

Specificity

Targets specific pathogens

Memory

Faster response upon re-exposure

Primary Response

First exposure; slower response

Secondary Response

Faster, stronger response

Immune Cells

B Lymphocytes (B Cells) & T Lymphocytes (T Cells)

B Lymphocytes (B Cells)

Produce antibodies

T Lymphocytes (T Cells)

Attack infected cells or help immune response

Antigen

Substance that triggers immune response

Epitope

Specific part of antigen recognized

Antibodies (Immunoglobulins)

Proteins that bind antigens

Antibody Structure

Heavy chain, light chain, variable region, constant region, disulfide bonds, antigen-binding site

Heavy Chain

Larger protein chain

Light Chain

Smaller protein chain

Variable Region

Binds antigen (specific)

Constant Region

Determines antibody class

Disulfide Bonds

Hold antibody structure together

Antigen-Binding Site

Region that attaches to antigen

Antibody Types

IgG, IgM,IgA, IgD, and IgE

IgG

Most abundant; long-term immunity

IgM

First antibody produced

IgA

Found in secretions (saliva, mucus)

IgD

Involved in B cell activation

IgE

Involved in allergies

Antibody Functions

Neutralization, Opsonization, Agglutination, Complement Fixation, ADCC

Neutralization

Blocks pathogen activity

Opsonization

Tags pathogens for destruction

Agglutination

Clumps pathogens together

Complement Fixation

Activates complement system

ADCC

Antibody-Dependent Cellular Cytotoxicity - Antibodies signal cells to kill target

Humoral Immunity

Antibody-mediated (B cells)

Cellular Immunity

T cell-mediated

T Cell Receptors (TCRs)

Recognize antigens

MHC-I

Presents antigens to cytotoxic T cells

MHC-II

Presents antigens to helper T cells

Antigen-Presenting Cells (APCs)

Display antigens (e.g., dendritic cells)

Antigen Presentation

Showing antigen to T cells

Helper T Cells

CD4 - Activate other immune cells

Cytotoxic T Cells

CD8- Kill infected cells

Regulatory T Cells

Suppress immune response

CD Molecules

Surface proteins that define T cells

Cell Processes

Selection, Activation, Differentiation, Apoptosis

Selection

Only useful lymphocytes survive

Activation

Lymphocytes respond to antigen

Differentiation

Become specialized cells

Apoptosis

Programmed cell death