The Immune System

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About 30 proteins make up the complement system, which causes lysis of invading cells and helps trigger inflammation.

Slide 16

Inflammatory Responses

Following an injury, mast cells release histamine, which promotes changes in blood vessels; this is part of the inflammatory response.

These changes increase local blood supply and allow more phagocytes and antimicrobial proteins to enter tissues.

Pus = a fluid rich in white blood cells, dead microbes, and cell debris, accumulates at the site of inflammation.

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Major events in a local Inflammatory Response

Pathogen

Splinter

Macrophage

Mast cell

Chemical

signals

Capillary

Phagocytic cell

Red blood cells

Fluid

Phagocytosis

1.

2.

3.

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Inflammation can be either local or systemic (throughout the body).

Fever is a systemic inflammatory response triggered by pyrogens released by macrophages, and toxins from pathogens.

Septic shock is a life-threatening condition caused by an overwhelming inflammatory response.

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Natural Killer Cells

All body cells (except red blood cells) have a class I MHC protein on their surface.

MHC = Major Histocompatibility Complex , part of the extracellular matrix.

Class II MHC protein molecules are found on specialized cells

Cancerous or infected cells no longer express this MHC protein; natural killer (NK) cells attack these damaged cells.

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Innate Immune System Evasion by Pathogens

Some pathogens avoid destruction by modifying their surface to prevent recognition or by resisting breakdown following phagocytosis.

Tuberculosis (TB) is one such disease and kills more than a million people a year.

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In Acquired Immunity, lymphocyte receptors provide pathogen-specific recognition

White blood cells called lymphocytes recognize and respond to antigens, foreign molecules.

Lymphocytes that mature in the thymus above the heart are called T cells, and those that mature in bone marrow are called B cells.

Lymphocytes contribute to immunological memory, an enhanced response to a foreign molecule encountered previously.

Cytokines are secreted by macrophages and dendritic cells to recruit and activate lymphocytes.

Slide 22

Acquired Immunity = Active Immunity: Specific