The Body Defenses Body Defense Overview Innate Immunity

The Body Defenses

Body Defense Overview • Innate Immunity – Barrier Defenses – Internal Defenses • Acquired Immunity – Humoral Response – Cell-mediated Response

Innate Immunity in Invertebrates (Nonspecific) • Chitin (physical barrier) in intestine • Lysozymes and low p. H (digests microbial cell walls) • Hemocytes in hemolymph – Phagocytosis – Antimicrobial peptides

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

Innate Immunity in Vertebrates Internal Defenses (Nonspecific) • Phagocytic White Blood Cells • The Inflammatory Response • Antimicrobial Proteins • Natural Killer Cells

Phagocytic White Blood Cells (Leukocytes) • Neutrophils (70%) – short lived • Monocytes (5%) – macrophages – long lived in lymphatic tissue • Eosinophils (1. 5%) – attack larger parasites

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 of Phagocytes (activate lymphocytes)

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

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

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

Acquired Immunity • Vertebrates – Uses Lymphocytes to recognize antigens – Two major types • B lymphocytes • T lymphocytes

The Development of Lymphocytes • B cells – made and mature in bone marrow • T cells – made in bone marrow and matures in thymus

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

Antigen Recognition by Lymphocytes • B Cells – Y shaped receptors made up of 4 polypeptide chains (two heavy / two light) • Recognize intact antigens

Antigen Recognition by Lymphocytes • T Cells – 2 polypeptide chains (an alpha chain and a beta chain) • Recognize small fragments of antigens

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 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 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 Antigens • Helper T cells – attach to macrophage that has attacked an antigen • often uses CD 4 receptors – releases interleukin (Cytokine) – activates Cytotoxic T cells and Plasma B cells

Cell-mediated Response • Cytotoxic T cells – – – attach to infected cells / Cancer Cells Usually uses a CD 8 receptor perforin (protein) makes a pore in membrane ions and water enters pores infected cell lyses

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 B cells quickly when reinfected by the same antigen

Antibodies • A group of globular serum proteins called immunoglobulins

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

Abnormal • Allergies Immune – hypersensitive responses to Function antigens – anaphylactic shock • Autoimmune Diseases – immune system attacks own body • Lupus, MS, ALS, Rheumatoid Arthritis • Immunodeficiency Diseases – lowered immune system – SCIDS, AIDS

Stages of HIV Infections