the body defenses

8/13/2019 The Body Defenses

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The Body Defenses


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Body Defense Overview

Innate Immunity

Barrier Defenses

Internal Defenses

Acquired Immunity Humoral Response

Cell-mediated

Response


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Innate Immunity in Invertebrates

(Nonspecific) Chitin (physical

barrier) in intestine

Lysozymes and low

pH (digests microbialcell walls)

Hemocytes in

hemolymph

Phagocytosis

Antimicrobial peptides


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Innate Immunity in Vertebrates

Barrier Defenses (Nonspecific) Skin Physical Barrier &

Lysozymes

Digestive Tract High acidity & normal

bacteria

Respiratory Tract Mucus & Cilia

Genitourinary Tract

Acidity of Urine


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Innate Immunity in Vertebrates

Internal Defenses

(Nonspecific) Phagocytic White

Blood Cells The Inflammatory

Response

Antimicrobial

Proteins

Natural Killer Cells


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Phagocytic White Blood Cells

(Leukocytes) Neutrophils (70%)

short lived

Monocytes (5%) macrophages

long lived in lymphatic tissue

Eosinophils (1.5%) attack larger parasites


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The Inflammatory Response Releases histamine

(basophils and mast cells)

Allows for dilation and increased permeability

Increased temp due to increased blood flow

Cytokines (protein) direct migration ofPhagocytes (activate lymphocytes)


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Antimicrobial Proteins

Compliment System

30 proteins

lyses viruses and pathogens

may attract phagocytes and cause adherence Two pathways

Alternative

triggered by substances on invaders and does not use

antibodies

Classical

triggered by antigens and uses antibodies


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Antimicrobial Proteins

Interferon proteins secreted by viral infected cells

diffuse to surrounding cells

surrounding cells make chemicals that inhibit

viral reproduction


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Natural Killer Cells Recognize damaged or diseased cells

Class 1 MHC molecule on surface of most cells

Missing when diseased

Release chemical to destroy cells lacking this

protein


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Acquired Immunity

Vertebrates

Uses Lymphocytes to recognize antigens

Two major types

B lymphocytes

T lymphocytes


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Epitopes

Antigenic determinant (special areas on

antigens

Usually has several


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Antigen Recognition by

Lymphocytes

B Cells Y shaped receptors made up of

4 polypeptide chains (two heavy / two

light)

Recognize intact antigens


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Major Histocompatibility Complex

Class 1 MHC

molecules

Work with

Cytotoxic T cells Class 2 MHC

molecules

Work with both

Cytotoxic T CellsHelper T cells


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Immune Response

Primary Immune

Response

Takes 10 - 17 days

from initial exposure toan antigen

Produces B and T

cells

Secondary Immune

Response

takes 2 - 7 days from

re-exposure to antigen


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Immune Responses

Humoral Immunity

involves B cells

produces antibodies

that circulate in theblood, plasma and

lymph

cells do not have to be

next to antigen to

attack

Cell-mediated

Immunity

involves T cells

cells must be next toantigens to attack


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Response to Nearly All Antigens

Helper T cells

attach to macrophage that has attacked an

antigen

often uses CD4 receptors

releases interleukin (Cytokine)

activates Cytotoxic T cells and Plasma B cells


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Cell-mediated Response Cytotoxic T cells

attach to infected cells / Cancer Cells

Usually uses a CD8 receptor

perforin (protein) makes a pore in membrane

ions and water enters pores

infected cell lyses


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B Cells: A Response to

Extracellular Pathogens Response to

extracellular

pathogens

Plasma B cells

produce antibodies

Memory B cells

live a long time

and can help

produce other Bcells quickly when

re-infected by the

same antigen


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Antibodies

A group of globular

serum proteins called

immunoglobulins


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Immunity in Health and Disease

Active Immunity

Getting the disease

Immunizations

(Vaccinations) Passive Immunity

Antibodies transferred

from one individual to

another pregnancy and breast

feeding

injection of antibodies


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Stages

of HIV

Infect-

ions

the body defenses

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