Ch 43 Body’s DefensesCh 43 Body’s Defenses

AP BiologyAP Biology

Vertebrate Nonspecific DefenseVertebrate Nonspecific Defense

Barriers, Phagocytes, Proteins, Complement Barriers, Phagocytes, Proteins, Complement System, & InflammationSystem, & Inflammation

1. Barriers [Skin] 1. Barriers [Skin] Prevents entry of pathogens (intact Prevents entry of pathogens (intact epidermis, hairs to filter, etc.)epidermis, hairs to filter, etc.)Secrete acids (inhibit growth of Secrete acids (inhibit growth of

microorganisms, destroy bacteria in microorganisms, destroy bacteria in food), mucous (wash away & trap), & food), mucous (wash away & trap), & chemicals (lysozyme to destroy cell chemicals (lysozyme to destroy cell walls)walls)

2. Phagocytes2. Phagocytes

Lysosomes within cells fuse with pathogens & Lysosomes within cells fuse with pathogens & release hydrolytic enzymesrelease hydrolytic enzymes

Neutrophils (phagocytosis of pathogens) Neutrophils (phagocytosis of pathogens) [W.B.C.][W.B.C.]

Monocytes (phagocytize pathogens) some are Monocytes (phagocytize pathogens) some are wandering (throughout interstitial fluid & lymph) wandering (throughout interstitial fluid & lymph) others are fixed (found in lymph nodes)others are fixed (found in lymph nodes)

EosinophilsEosinophils

Killer cells (kill infected cells)Killer cells (kill infected cells)

3. Proteins3. Proteins

Interferons (Interferons (interfere with viral reproductioninterfere with viral reproduction))

Secreted by infected cells, stimulate Secreted by infected cells, stimulate neighboring cells to produce antiviral neighboring cells to produce antiviral proteins to inhibit growth of virus.proteins to inhibit growth of virus.

Active only against viruses.Active only against viruses.

Recombinant DNA technology used to Recombinant DNA technology used to make synthetic forms in hope of slowing make synthetic forms in hope of slowing cancer growth.cancer growth.

4. Complement System4. Complement System

Attract phagocytes [found in plasma]Attract phagocytes [found in plasma]

Triggered by antibodies to antigenTriggered by antibodies to antigen

5. Inflammation5. Inflammation

Cells release histamine causing dilation of vessels.Cells release histamine causing dilation of vessels.Increase blood supply due to dilation causes redness Increase blood supply due to dilation causes redness and warmth.and warmth.Swelling (edema) of affected area caused by fluid loss Swelling (edema) of affected area caused by fluid loss from vessels. from vessels. Vessels become more permeable/leaky (caused by Vessels become more permeable/leaky (caused by histamine)histamine)Increased blood flow brings larger numbers of Increased blood flow brings larger numbers of phagocytes to infected area.phagocytes to infected area.Fever – widespread inflammatory response. Pyrogens Fever – widespread inflammatory response. Pyrogens (released by W.B.C.s) reset thermostat in hypothalamus.(released by W.B.C.s) reset thermostat in hypothalamus.Fever interferes with viral activity.Fever interferes with viral activity.

Vertebrate Specific DiseaseVertebrate Specific Disease

SpecificitySpecificity

DiversityDiversity

Self/non-self recognitionSelf/non-self recognition

MemoryMemory

SpecificitySpecificity

Response is not random. Recognition and Response is not random. Recognition and elimination of elimination of particularparticular microorganism microorganism and pathogen.and pathogen.Body responds to antigen (substance that Body responds to antigen (substance that initiates response [capsule, cell wall, initiates response [capsule, cell wall, toxin]; unique molecular shaped conferred toxin]; unique molecular shaped conferred by surface proteins) by releasing antibody by surface proteins) by releasing antibody (protein produced by B-cells that bind to (protein produced by B-cells that bind to antigens)antigens)

DiversityDiversity

Antibody amino acid sequence on variable Antibody amino acid sequence on variable region constantly modified.region constantly modified.

Self/Non-self RecognitionSelf/Non-self Recognition

Blood groups, tissue grafts and organ Blood groups, tissue grafts and organ transplants, autoimmune disorders.transplants, autoimmune disorders.

Major histocompatibility complex (MHC). Major histocompatibility complex (MHC). Proteins embedded in plasma Proteins embedded in plasma membranes.membranes.

MemoryMemory

Memory cells survive in system for long Memory cells survive in system for long period of time. Activated during secondary period of time. Activated during secondary immune response.immune response.

3 steps to Immune Response3 steps to Immune Response

1.1. Recognition of Invader [Caught on Recognition of Invader [Caught on Radar]Radar]

2.2. Activation of System [Man your Battle Activation of System [Man your Battle Stations!]Stations!]

3.3. Response to Invader [Fire all weapons!!]Response to Invader [Fire all weapons!!]

Active ImmunityActive Immunity

Individual is infected and forms a defense Individual is infected and forms a defense against pathogen by mounting either a humoral against pathogen by mounting either a humoral response (antibody formation) or a cell-mediated response (antibody formation) or a cell-mediated response (lymphocytes)response (lymphocytes)

Vaccinations (weakened forms of pathogen or Vaccinations (weakened forms of pathogen or toxin) stimulate antibody production and toxin) stimulate antibody production and formation of memory cells without causing the formation of memory cells without causing the disease. Vaccines are made from killed disease. Vaccines are made from killed pathogens or weakened strains that cause pathogens or weakened strains that cause antibody production but not the disease.antibody production but not the disease.

Passive ImmunityPassive Immunity

Transferred from one individual to another Transferred from one individual to another (mother to baby). Antibodies are (mother to baby). Antibodies are transferred in colostrum of nursing moms.transferred in colostrum of nursing moms.

Antibodies can be give to adults as well.Antibodies can be give to adults as well.

Temporary jump start to immunity. Work Temporary jump start to immunity. Work long enough to prevent infection.long enough to prevent infection.

RuleRule

Once the immune system has been Once the immune system has been activated (actively or passively) the activated (actively or passively) the response can be the formation of response can be the formation of antibodies (humoral) or lymphocytes (cell-antibodies (humoral) or lymphocytes (cell-meidated).meidated).

Humoral ResponseHumoral Response

Antibodies are Y shaped protein Antibodies are Y shaped protein molecules composed of two identical long molecules composed of two identical long polypeptides and two identical short polypeptides and two identical short polypeptides.polypeptides.

Function of antibodies include:Function of antibodies include:– Recognition and binding to antigenRecognition and binding to antigen– Inactivation of the antigenInactivation of the antigen

Humoral Response cont.Humoral Response cont.Regulated by B-cells. (B-cells form & develop Regulated by B-cells. (B-cells form & develop from stem cells in marrow)from stem cells in marrow)

-Concentrated in lymph nodes, spleen. (Spleen -Concentrated in lymph nodes, spleen. (Spleen is largest lymphatic structure. It is responsible is largest lymphatic structure. It is responsible for the production of B-cells, phagocytizes for the production of B-cells, phagocytizes bacteria and worn out/damaged R.B.C.s, stores bacteria and worn out/damaged R.B.C.s, stores and releases blood in case of demand (i.e. and releases blood in case of demand (i.e. hemorrhage)hemorrhage)

Have antigen receptors on membrane to Have antigen receptors on membrane to recognize specific pathogen. Can only bind to recognize specific pathogen. Can only bind to one type of antigen.one type of antigen.

Humoral Repsonse cont.Humoral Repsonse cont.

Plasma CellsPlasma Cells– Secrete antibodies specific for antigen Secrete antibodies specific for antigen

(approx. 2000 molecules/sec.)(approx. 2000 molecules/sec.)

B-memory cells are also formed to provide B-memory cells are also formed to provide immunological memory (life for months or immunological memory (life for months or years). During secondary response, react years). During secondary response, react much more quickly and aggresively.much more quickly and aggresively.

Cell-mediated ResponseCell-mediated Response

Lymphocytes respond to antigen.Lymphocytes respond to antigen.

Work together w/ macrophages that have Work together w/ macrophages that have engulfed pathogen. Surface of engulfed pathogen. Surface of macrophage has signals (self v. non-self) macrophage has signals (self v. non-self) that are recognized by lymphocytes.that are recognized by lymphocytes.

T lymphocytes (T-cells) form from T lymphocytes (T-cells) form from pluripotent stem cells, develop in thymus.pluripotent stem cells, develop in thymus.

Cell-mediated Response cont.Cell-mediated Response cont.

Cells only activated by cells previously Cells only activated by cells previously infected with an antigen (Cell-to-Cell infected with an antigen (Cell-to-Cell combat)combat)

Cannot recognize free floating antigens in Cannot recognize free floating antigens in body fluids (unlike antibodies). Once body fluids (unlike antibodies). Once activated, T-cells become specialized activated, T-cells become specialized forms called helper T (Tforms called helper T (THH) or ) or

killer/cytotoxic T (Tkiller/cytotoxic T (TCC))

Cell-mediated Response cont.Cell-mediated Response cont.