Topic 9

Immunity

Ability of organism to resist infection

Competitive exclusion

Pathogens compete with normal microbiota and have less nutrients and space

Primary effector cells of innate immunity

Phagocytes

Primary effectors cells of adaptive immunity

Lymphocytes

Innate immunity

General, no memory, immediate response

Adaptive immunity

Specific, memory, delayed response

Leukocytes

White blood cells

Plasma

Liquid portion of blood

Serum

Portion of blood without cells or clotting agents

Lymph nodes

Contain high concentrations of immune cells

Where does lymph exchange occur?

Capillary beds

Lymphocytes

Specialized WBCs exclusive to adaptive immunity

B cells

Mature in bone marrow

T cells

Mature in thymus

What cells are involved in antigen presentation?

Dendritic cells and macrophages

What cells are involved in phagocytosis

Neutrophils, eosinophils, macrophages, and dendritic cells

What cells are involved in innate immunity?

Dendritic cells, macrophages, neutrophils, eosinophils, basophils, mast cells, and natural killer cells

2 hours after infections

Phagocytes respond

4 hours after infection

Inflammation

6 hours after infection

Antiviral defense

10 hours after infection

Antigen presentation

Pathogen-associated molecular patterns

Components of pathogens that can be recognized by immune cells

Pattern recognition receptor

Structure on surface of immune cells that recognizes PAMPs

Toll like receptors

Send signal to nucleus to change gene expression. Recognizes specific PAMP

Cytokines and chemokines

Chemical messengers that mediate immune response

What attracts phagocytes to sites of infection?

cytokine-chemokine gradient

Phagocytosis

Engulfing pathogen

Stages of phagocytosis

Chemotaxis, adherence, Ingestion, killing/elimination

Phagosome

Vesicle in cell to hold foreign material

Lysosome

Digests contents of phagosome

Inflammation

Nonspecific reation to noxious stimuli

What do mast cells release?

Histamine

What do macrophages release?

Cytokines

Pyrogens

Fever causing cyotkines

What is the purpose of fever?

Increase ciruclation and burn pathogens

Local inflammation

Occurs at site of infection

Systemic infection

Causes shock

Interferons

Proteins produced by virally infected cells or tumors

Natural killer cells

Innate immunity, attack virally infected and tumor cells

Major histocompatibility complex

Structure found on normal cells

What do virally infected or tumor cells show on their surface?

Stress signals

Granzymes

Cause apoptosis

Perforins

Poke holes in target cell membrane

Complement system

Protein cascade that is 3 fold

Specificity

Lymphocytes have surface receptos that interact with specific antigens

Antigens

Substances that react with antibodies or Toll like receptors

Immunogen

Induce an immune response

Epitope

Specific region on an antigen that antibody interacts with

Antibody

Protein made by B lymphocytes or plasma cells in response to antigen exposure

What is the most common antibody in the human body?

IgG

IgM

Early response

IgA

Present in bodily fluids

IgE

Allergies

IgD

Present in serum

Steps in adaptive immunity

Antigen presentation, T cell activation, B cell expansion

Helper T cells

Activate B cells after interacting with antigen presenting cell

Cytotoxic T cells

Attack and kill infected cells

B cell receptor

Binds to antigen

What do B cells become?

Plasma cells or Memory cells

Plasma cells

Short lived, Produce antibodies to fight active infection

Memory B cells

Long lived, Trigger immune response upon reinfection with same pathogen

What happens upon secondary infection?

Memory cells become plasma cells to fight infection

Agglutination

Clump antigens together, reducing number of cells (Many small cells vs 1 large clump)

Opsonization

Make it easier to phagocytize

Neutralization

Block access to host tissues

Atibody-dependent cell mediated cytotoxicity

External cells bind to antibodies covering pathogen and release chemicals to lyse it

Humoral

B cells

Cell-mediated immunity

Cytotoxic T cells

Regulatory T cells

Inhibit T and B cells activity