The Body DefensesThe Body Defenses

Body Defense OverviewBody Defense Overview

• Innate Immunity– Barrier Defenses– Internal Defenses

• Acquired Immunity– Humoral Response– Cell-mediated

Response

Innate Immunity in InvertebratesInnate Immunity in Invertebrates(Nonspecific)(Nonspecific)

• Chitin (physical barrier) in intestine

• Lysozymes and low pH (digests microbial cell walls)

• Hemocytes in hemolymph – Phagocytosis– Antimicrobial peptides

Innate Immunity in Vertebrates Innate Immunity in Vertebrates Barrier Defenses (Nonspecific)Barrier Defenses (Nonspecific)

• Skin– Physical Barrier & Lysozymes

• Digestive Tract– High acidity & normal bacteria

• Respiratory Tract– Mucus & Cilia

• Genitourinary Tract– Acidity of Urine

Innate Immunity in Vertebrates Innate Immunity in Vertebrates Internal DefensesInternal Defenses

(Nonspecific)(Nonspecific)• Phagocytic White

Blood Cells• The Inflammatory

Response• Antimicrobial

Proteins• Natural Killer Cells

Phagocytic White Blood CellsPhagocytic White Blood Cells(Leukocytes)(Leukocytes)

• Neutrophils (70%)– short lived

• Monocytes (5%) – macrophages– long lived in lymphatic tissue

• Eosinophils (1.5%)– attack larger parasites

The Inflammatory ResponseThe 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 of Phagocytes (activate lymphocytes)

Antimicrobial ProteinsAntimicrobial 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

Antimicrobial ProteinsAntimicrobial Proteins

• Interferon– proteins secreted by viral infected cells– diffuse to surrounding cells– surrounding cells make chemicals that inhibit viral

reproduction

Natural Killer CellsNatural 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

Acquired ImmunityAcquired Immunity

• Vertebrates– Uses Lymphocytes to recognize antigens– Two major types

• B lymphocytes• T lymphocytes

The The Development of Development of

LymphocytesLymphocytes• B cells

– made and mature in bone marrow

• T cells– made in bone

marrow and matures in thymus

EpitopesEpitopes

• Antigenic determinant (special areas on antigens– Usually has several

Antigen Recognition by Antigen Recognition by LymphocytesLymphocytes

• B Cells – Y shaped receptors made up of 4 polypeptide chains (two heavy / two light)

• Recognize intact antigens

Antigen Recognition by Antigen Recognition by LymphocytesLymphocytes

• T Cells – 2 polypeptide chains (an alpha chain and a beta chain)

• Recognize small fragments of antigens

Major Histocompatibility Complex Major Histocompatibility Complex

• Class 1 MHC molecules– Work with

Cytotoxic T cells

• Class 2 MHC molecules– Work with both

Cytotoxic T Cells Helper T cells

Immune ResponseImmune Response

• Primary Immune Response– Takes 10 - 17 days

from initial exposure to an antigen

– Produces B and T cells

• Secondary Immune Response– takes 2 - 7 days from

re-exposure to antigen

Immune ResponsesImmune Responses

• Humoral Immunity– involves B cells– produces antibodies

that circulate in the blood, plasma and lymph

– cells do not have to be next to antigen to attack

• Cell-mediated Immunity– involves T cells– cells must be next to

antigens to attack

Response to Nearly All AntigensResponse 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

Cell-mediated ResponseCell-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

B Cells: A Response to B Cells: A Response to Extracellular PathogensExtracellular Pathogens

– Response to extracellular pathogens

– Plasma B cells produce antibodies

– Memory B cells live a long time and can help produce other B cells quickly when re-infected by the same antigen

AntibodiesAntibodies

• A group of globular serum proteins called immunoglobulins

Immunity in Health and DiseaseImmunity 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

Abnormal Immune Abnormal Immune FunctionFunction

• Allergies– hypersensitive responses to

antigens

– anaphylactic shock

• Autoimmune Diseases– immune system attacks own body

• Lupus, MS, ALS, Rheumatoid Arthritis

• Immunodeficiency Diseases– lowered immune system

– SCIDS, AIDS

Stages Stages of HIV of HIV Infect-Infect-ionsions