Chapter 24- The Immune System Active immunity Allergen Allergies Anaphylactic shock Antibody Antigen Antigen receptors Antigen-binding site Antigenic determinants Antigen-presenting cells Antihistamine Autoimmune diseases B cells Cell-mediated immunity Clonal selection Complement proteins Cytotoxic T cells Helper T cells Histamine Humoral immunity Immune system Immunity Immunodeficiency diseases Inflammatory response Interferons Lymph Lymphatic system Lymphocytes Macrophages Major histocompatibility complex Mast cells Memory cells Monoclonal antibodies Monocytes Natural killer cells Neutrophils Nonself molecules Passive immunity Perforin Plasma cells Primary immune response Secondary immune response Self protein T cells Vaccination Vaccine

Immune system Protects the body by recognizing and attacking specific kinds of pathogens and cancer cells There are both nonspecific and specific responses against infection

1st line of defense is nonspecific Nonspecific = (can’t distinguish a certain pathogen) Intact skin- barrier that pathogens can’t penetrate Acids secreted by glands in skin- inhibit microbe growth Sweat, saliva, tears- contain lysozyme- an enzyme that attacks bacterial cell walls Digestive and respiratory systems- guarded by mucous membranes (b/c they are exposed to env) Stomach acid- kills bacteria Hair in nostrils- filters air Mucous in respiratory system traps particles and cilia sweep them out

Nonspecific defense cells Neutrophils, monocytes and macrophages- engulf bact and viruses Natural killer cells- attack cancer cells and infected body cells (especially those that harbor viruses)

Proteins also attack microbes or impede reproduction Interferons- proteins that are produced by cells that are infected by a virus to help other cells resist virus Nonspecific, short term, can be used to treat certain cancers Complement proteins- circulate in plasma, activated by immune system or microbes, stick to surfaces for macrophages to notice, cut holes in cells, amplify nonspecific responses

Inflammatory response

Inflammatory response Major component of nonspecific defense red, swollen, warm “inflamed” –due to increase in blood flow, fluid and cells Damaged skin releases chem signal (histamine) It induces blood vessels to dilate and become leaky Blood flow to area increase, plasma moves to interstitial fluid Other chem’s attract phagocytes Results: disinfect area, engulf bacteria Clotting proteins- seal off infected region Response can be local or systemic (WBC’s increase, fever, high fever, low BP-septic shock)

The Lymphatic System Returns tissue fluid to circ system and fight infection Consists of: vessels, lymph nodes, tonsils, adenoids, appendix, spleen, bone marrow, thymus Involved in: nonspecific and specific resistance to infection System is where fluid that has left circ system returns to, happens by diffusion Infection fighting occurs in lymph nodes and other vessels which are packed with WBC’s Sometimes they become swollen when fighting infection

The Lymphatic System

Specific Immunity Immunity- resistance to specific invaders Active- when antigens enter body (getting sick/a shot) Passive- antibodies are passed (fetus from placenta, sometimes when travelling to other countries) Antigen- “antibody generating”- elicits immune response Molecules on surfaces of cells Antibody- protein in blood plasma that attaches to particular antigen and help counter its effect *****has a good memory*****

Lymphocytes White blood cells Originate in bone marrow Spend most of their time in tissues and organs of lymphatic system Produce specific immune responses Response to antigens in 2 ways:

Lymphocytes Mature in thymus =T cells Mature in bone marrow= B cells Cell-mediated immunity Attacks infected body cells Promotes phagocytosis and stimulates B cells (so T cells are involved in both) Can be transferred passively (injecting T cells) Mature in bone marrow= B cells Humoral immunity Secretes antibodies Can be transferred passively (injecting antibodies) Antigen receptors- molecules on cells surface, bind to antigen 100mil to 100bil different kinds of B and T cells!

Lymphocytes

Antigens Most are proteins or polysaccharides Antigenic determinants- region that antibody recognizes Site on antibody (antigen-binding site)- recognizes determinant *complementary shape

Antigens Activate lymphocytes to multiply that are specific to the antigen- clonal selection Effector cells produced secrete antibodies This happens with B cells and T cells

Primary Immune Response 1st time lymphocytes are exposed to antigen and clonal selection happens Takes a few days before lymphocytes are activated

Secondary Immune Response After 2nd exposure to same antigen Produces very high antibody levels, lasts longer Each antigen exposure triggers clonal selection Cells of the clone include: Memory cells- last for decades, remain in lymph nodes, when activated-trigger secondary response, multiply quickly Effector cells- produce antibodies

Humoral vs. Cell-mediated Immunity

Humoral Immunity In body fluids Effector cells produced during clonal selection are called plasma cells Plasma cells then secrete antibodies

Antibodies 2 heavy chains and 2 light chains bonded together 2 functions: recognize and bind to antigen & neutralize the antigen Structure allows function Antigen-binding sites in V region Mark antigens for elimination Binding creates antigen-antibody complex

Methods for antigen inactivation: Neutralization- antibodies block antigens from binding with cells, phagocytes engulf complex Agglutination- “clumping” – clumps invaders together making it easier for phagocytes to capture Precipitation- link antigen molecules together and they precipitate out of solution as solids, easily engulfed Activation of complement proteins by antigen-antibody complex- proteins open holes in plasma membrane, cell lyses

Monoclonal antibodies Antibody secreted by a clone of cells that’s specific for an antigen Ex: pregnancy test- binds to hormones, STD test-binds to bacteria

Cell-mediated Immunity T cells respond to antigens on body’s own cells Cytotoxic T cells- attack infected body cells Helper T cells- help activate cytotoxic T’s and macrophages, and stimulate B’s to produce antibodies Antigen-presenting cells (APC’s) – present antigens to helper T’s- triggering pathway to activate helper T’s

When a T cell is activated: Grow and divide, producing more helper T and memory T cells Stimulate cytotoxic T’s Bind to infected cells and form holes in membrane Activate B cells Cytotoxic T cells also can recognize changes in membranes of cancerous cells and destroy them

Immune system depends on our molecular fingerprint Recognizes “self” and “non-self” What if that doesn’t work?

Immune System Disorders Autoimmune disease- immune system attacks body’s own cells MS, lupus, insulin-dependent diabetes

Immune System Disorders Immunodeficiency disease- when a component of the system is lacking Can be caused by physical and emotional stressors AIDS, SCID, Hodgkins disease HIV virus destroys helper T cells Allergies- overreaction of the immune system Antigens that cause allergies are called allergens