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 pH (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 days from initial exposure to an antigen –Produces B and T cells Secondary Immune Response –takes 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 CD4 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 CD8 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 re-infected 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 Immune Function 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 of HIV Infect- ions