MIC301 Exam 3 CH. 11 INNATE RESPONSE

Immune response

A physiological process coordinated by the immune system to eliminate antigens

Immune

Resistant to a pathogen or microbe

Susceptible

Not immune to given pathogen

Innate and adaptive shared traits

Recognize diverse pathogens

Eliminate identified invaders

Discriminate between self and foreign antigens

Innate immunity

We are all born with it

Generalized responses

Non-specific

Adaptive immunity

Responses tailor to pathogens

Exhibits memory

Longer to activate

Hygiene hypothesis

If you are less exposed to different microbes, you will have underdeveloped immune system

Benefits of normal microbiota

Compete for nutrients with pathogens

Compete for space with pathogens

Make substances that may directly damage pathogens

Generate an environment that limits pathogen survival

First line of defense

Mechanical, chemical and physical barriers

Mechanical barriers

Rinse, flush, or trap pathogens to limit their spread into the body

Ex. tears, urine, saliva, mucus membranes

Chemical barriers

May directly attack invaders or establish environments that limit pathogen survival in or on a particular tissue

Ex. lysozymes, stomach acid, salty skin, fatty acids, AMPS

AMPs

Proteins that destroy a wide spectrum of viruses, parasites, bacteria, and fungi

Can activate leukocytes to clear pathogens

Can act on the cell wall of pathogens

Can act on the intracellular components of bacteria

Defensins

AMPs that rapidly kill invaders by inserting themselves into target cell membranes

Physical barriers

Include structures that physically block pathogen entry

Ex. epithelial tissue, skin, epidermis

Second line of defense

Kick in when first line is breached

Consist of assorted molecular factors (proteins) and leukocytes

Granulocytes

Cells with granules in their cytoplasm that are visible when stained

Agranulocytes

Lack granules in cytoplasm

Phagocytes

Target bacterial cells, viral particles, or general debris and EAT THEM!

Macrophages, dendritic cells, and neutrophils

Phagosome

Holds the bacteria inside of it

Lysosomes release enzymes to kill the material

Neutrophils

Most numerous WBC in circulation

Multilobed segmented nucleus

First cells to go to injured tissue

Release AMPs

Phagocytize foreign cells and viruses

Increased neutrophil count means…

Acute bacterial infection

Neutropenia

Low neutrophil count

Caused by certain viral infections

Eosinophils

Bind to acid dye “Eosin”

Specific to allergens and microbes - especially parasites

Basophils

Combat parasitic infections and have a role in allergic responses

Mast cells

Reside in tissues

Play a role in allergies and fighting parasites

Main role is to secrete histamine

Common in tissues near body openings

Monocytes (Macrophages)

Largest agranular WBC

Levels can increase due to chronic infections and inflammation, autoimmune disorders, and certain cancers

Migrate out of circulatory system into tissues and mature into macrophages

Macrophages

Highly phagocytic

Destroy a wide range of pathogens

Fixed: reside in specific tissues

Wandering: roam through tissues

Dendritic cells

Highly phagocytic

Found in most body tissues

Abundant in tissues next to body openings

Patrol tissues and phagocytize a broad range of antigens

Prevent immune system from attacking self and overreacting to nonthreatening substances

Lymphocytes

Include NK cells, B cells, T cells

NK Cells

Natural killer cells

Innate protection against viruses, bacteria, parasites, and tumor cells

THEY KILL STUFF

Defense molecules

Mediate innate immune responses

Cytokines, iron-binding proteins, complement proteins

Cytokines

Signaling proteins that allow cells to communicate with each other, initiating and coordinating immune actions

Alarms!

Chemokines

Attract white blood cells to areas

Help with actual movement of cells towards an area

Induce chemotaxis

Interleukins

Activate adaptive and innate immune responses

Activate the cells

Stimulate hematopoiesis (blood cell formation)

IL-1

Regulates inflammation, stimulates innate and adaptive immune responses, generates fever

IL-2

Central to T cell development, self-tolerance, triggering apoptosis

Interferons

Interfere with viral replication

Signals neighboring cells to prepare antiviral defenses

Iron-binding proteins

Iron is a vital nutrient for cells

Hemoglobin

Ferritin

Lactoferrin

Transferrin

Bind the iron so the organism doesn’t have iron freely floating for bacteria to take

Hemolytic bacteria

Break down RBCs to get to iron-rich hemoglobin inside

Complement system

Inactive components

No infection/injury, then stay inactive

Complement proteins only activated if there is a need for activation

Serine proteases: activate other components

Lectin pathway

Binding of proteins on bacterial surface leads to activation of complement components and leads to formation of C3b. C3a diffuses away

Mannose-binding lectins

End goal is to form C3b

Classical pathway

Antibodies is starting point

Binding of C1 component on the bacterial surface leads to activation of complement components and leads to formation of C3b. C3a diffuses away

Alternate pathway

Activation of complement occurs spontaneously

No need for intermediate protein or antibody

Leads to formation and deposition of C3b on the bacterial surface while C3a diffuses away

Complement cascade and outcomes

Opsonization

Formation of a membrane attack complex which causes cytolysis

Inflammation

Opsonization

C3b coats surface of bacteria and helps phagocytic cells engulf bacteria

Makes it easier for phagocytes to engulf

Cytolysis (MAC)

Binding of C3b pokes hole on microbial cell surface which leads to the lysis of the microbial cell

Components of cell leak out

Inflammation

Innate immune response that develops when tissues are damaged

Cytokines, complement proteins, other pro-inflammatory factors

Redness

Pain

Localized heat

Swelling

Loss of function

Tissue injury initiates blood-clotting cascades

Blood clots curb blood loss and limit pathogen spread

Three main goals of inflammation

Recruit immune defenses to injured tissue

Limit the spread of infectious agents

Deliver oxygen, nutrients, and chemical factors essential for tissue recovery

Inflammation phases

1. Vascular changes: blood vessels dilate and become more permeable

2. Leukocyte recruitment: recruit innate immune cells to clear up debris

3. Resolution: early; blood vessels begin to revert to normal and swelling decreases. late; damages tissues are reparied, angiogenesis builds new blood vessels, blood clots dissolve, pus may form

Fever

Systemic innate immune response

Pyrogens: fever-inducing agents

Signal the hypothalamus to raise the body’s baseline temperature

Enhances antiviral effects of interferons

Increases phagocyte efficiency

Enhances leukocyte production