exam 2

Exam 2

Immune System

• Part 1 Innate Defenses

Surface Barriers: Skin and mucosae

Innate internal defenses: Cells; Phagocytes, Natural killer cells, Inflammation, Antimicrobial proteins, fever

• Part 2 Adaptive Defenses

• Antigens

• Lymphocytes and antigen-presenting cells

Humoral immune response > B Cells

Cellular immune response > T Cells

Tissue injury

Repair by connective tissue involves the influx of debris-removing inflammatory cells, formation of granulation tissue (a substance consisting of fibroblasts and delicate capillaries in a loose extracellular matrix) and conversion of said granulation tissue into fibrous tissue that is remodeled over time to form a scar

Phagocytosis:

Phagocyte adheres to Pathogens or debris

Phagocyte forms pseudopods that eventually engulf the particles, forming a phagosome

Lysosome fuses with the phagocytic vesicle, forming a phagolysosome

Lysosomal enzymes digest the particles, leaving a residual body

Exocytosis of the vesicle removes indigestible and residual material

Phagocyte mobilization: Phagocytes migrate into tissues to combat infection and maintain tissue homeostasis

Leukocytosis: Neutrophils enter blood from bone marrow

Margination: Neutrophils cling to capillary wall

Diapedesis: Neutrophils flatten and squeeze out of capillaries

Chemotaxis: Neutrophils follow chemical trail

Innate defenses -> Internal defenses

Virus enters cell and replicates

Interferon genes switch on

Cell produces interferon molecules

Interferon binding stimulates cell to turn on genes for antiviral proteins

Antiviral proteins block viral reproduction

Second line of Defense: Innate cellular

Phagocytes: Engulf & destroy pathogens that breach surface barriers

Natural Killer (NK) Cells: Promote apoptosis (cell death) by attacking virus-infected or cancerous body cells

Inflammatory response: Prevents injurious agents from spreading to nearby tissues, disposes of pathogens & dead tissue cells & promotes tissue repair (attracts phagocytes to area)

Interferons: Proteins released by virus-infected cells; act as chemical messengers to protect uninfected tissue cells from viral takeover

Fever: High body temperature inhibits microbes from multiplying

Adaptive Response

Origin: Both B and T lymphocyte precursors originate in red bone marrow

Maturation: Lymphocyte precursors destined to become T cells migrate to the thymus and mature there | B cells mature in the bone marrow

Seeding: Secondary lymphoid organs and circulation; immunocompetent but still naïve lymphocytes leave thymus and bone marrow and circulate through blood and lymph

Antigen encounter and activation: When a lymphocyte antigen receptors bind its antigen, that lymphocyte can be activated

Proliferation and differentiation: Activated lymphocytes multiply and then differentiate into effector cells and memory cells

Humoral Immunity

Active Naturally acquired; Infection- contact with pathogen

Active Artificially acquired; vaccine- dead or attenuated pathogens

Passive naturally acquired; antibodies passed from mother to fetus via placenta or to infant in her milk

Passive artificially acquired; injection of exogenous antibodies (gamma globulin)