OTHER PATHOGENS

THE BODY’S DEFENSESChapter 43

Overview: Recognition and Response

➤ Pathogens - any agents that cause disease ___________________________________________

➤ Innate immunity - defense active immediately upon infection; present from birth; nonspecific

➤ Adaptive immunity - found in vertebrates; AKA acquired immunity; specific

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Pathogens (such as bacteria,fungi, and viruses)

INNATE IMMUNITY (all animals)

• Rapid response

Recognition of traits sharedby broad ranges of pathogens, using a smallset of receptors

•

Recognition of traits specific to particular pathogens, using a vast array of receptors

•

• Slower response

Barrier defenses:SkinMucous membranes Secretions

Internal defenses:Phagocytic cells Natural killer cells Antimicrobial proteins Inflammatory response

Humoral response:Antibodies defend against infection in body fluids.

Cell-mediated response:Cytotoxic cells defendagainst infection in body cells.

ADAPTIVE IMMUNITY (vertebrates only)

Figure 43.2

Innate Immunity of Vertebrates

➤ Innate defenses include: ➤ barrier defenses ➤ phagocytosis ➤ antimicrobial proteins ➤ natural killer cells ➤ inflammatory response

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1st Line of Defense

Barrier Defenses - 1st Line of Defense

➤ include skin & mucous membranes of respiratory, urinary & reproductive tracts

➤ mucus traps & allows for removal of microbes

➤ many body fluids (saliva, mucus, tears) are hostile to microbes

➤ low pH of skin & digestive system prevents growth of many bacteria

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2nd Line of Defense

Phagocytic Cells - 2nd Line of Defense

➤ Pathogens entering the mammalian body are subject to phagocytosis

➤ A white blood cell engulfs a microbe, then fuses with a lysosome to destroy the microbe

➤ Phagocytic cells recognize groups of pathogens by TLRs, Toll-like receptors

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Types of Phagocytic Cells

➤ monocytes = become macrophages or dendritic cells

➤ neutrophils = engulf and destroy pathogens; 50-60% of circulating WBCs

➤ macrophages = are found throughout the body ➤ dendritic cells = travel to lymphatic system;

stimulate development of adaptive immunity (B & T cells)

➤ eosinophils = <5% of circulating WBCs; related to fighting parasites & sometimes allergies

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Natural Killer Cells - 2nd Line of Defense

➤ Circulate through body using lymphatic system

➤ Detect abnormal cells

➤ Release chemicals causing cell death

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Antimicrobial Proteins- 2nd Line of Defense

➤ Interferon = proteins interfere with viruses and help activate macrophages

➤ Complement system = approx. 30 different proteins; causes lysis of invading cells; helps trigger inflammation

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Inflammatory Response - 2nd Line of Defense

➤ Mast cells, a type of connective tissue, release histamine, which triggers blood vessels to dilate and become more permeable

➤ Activated macrophages and neutrophils release cytokines, signaling molecules promote blood flow to the area

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Figure 43.8-3

Pathogen Splinter

Mastcell

Macro-phage

Capillary

Redblood cells

Neutrophil

Signalingmolecules

Movementof fluid

Phagocytosis

➤ Inflammation can be either local or systemic

➤ Fever is a systemic inflammatory response triggered by activated macrophages and toxins released from pathogens

➤ Septic shock is a life-threatening condition caused overwhelming inflammatory response

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Impacts of the 2nd Line of Defense

2nd Line of Defense Applications

➤ Allergic Reactions

➤ Harmless substance treated like a pathogen

➤ Antigen on allergen binds to IgE receptors on mast cells

➤ Release histamine ➤ Various sensitivities

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ALLERGIC RESPONSE