Chapter 15 Immunity

Question 1

What are the two main types of immunity that make up the immune system?

Answer 1

The two types are innate nonspecific immunity which is inherited and adaptive specific immunity which is learned from exposure to specific pathogens and involves lymphocytes.

Question 2

What are some key components of innate immunity serving as the first line of defense?

Answer 2

Key components include physical barriers like the epidermis and mucous membranes high acidity in the stomach phagocytes that engulf and kill pathogens fever antimicrobial peptides and interferons.

Question 3

How do physical barriers protect against pathogens in innate immunity?

Answer 3

Epithelial membranes such as the skin and mucous membranes act as physical barriers preventing penetration by pathogens; for example skin secretions contain lysozyme that destroys bacteria.

Question 4

What role does stomach acidity play in innate immunity?

Answer 4

High acidity in the stomach helps kill pathogens that enter through the digestive tract serving as a protective chemical barrier.

Question 5

What are phagocytes and what is their function in innate immunity?

Answer 5

Phagocytes are immune cells that ingest and destroy bacteria cellular debris denatured proteins and toxins as part of the body’s internal defense mechanisms.

Question 6

What is the complement system and how does it function in innate immunity?

Answer 6

The complement system consists of plasma proteins that are activated when antibodies bind to antigens promoting phagocytosis lysis of target cells and local inflammation thereby integrating innate and adaptive immune responses.

Question 7

What are pathogen-associated molecular patterns (PAMPs) and how do immune cells recognize them?

Answer 7

PAMPs are unique molecular structures found on pathogens such as lipopolysaccharides in Gram-negative bacteria and peptidoglycan in Gram-positive bacteria recognized by pathogen recognition receptors on immune cells to distinguish self from nonself.

Question 8

How do immune cells respond upon recognizing PAMPs?

Answer 8

They secrete chemokines to attract more immune cells and activate specific cells and cytokines to promote various aspects of both innate and adaptive immune responses.

Question 9

What functions do natural killer (NK) cells serve within innate immunity?

Answer 9

NK cells destroy cells infected with viruses tumor cells and mismatched transplanted tissue cells as part of internal defenses.

Question 10

What are the three types of phagocytic cells mentioned and which one arrives first at an infection?

Answer 10

Three types exist with neutrophils being the first to arrive at an infection.

Question 11

What types of phagocytic cells arrive later at an infection after neutrophils?

Answer 11

Mononuclear phagocytic cells such as monocytes in the blood and macrophages and dendritic cells in the tissues arrive later.

Question 12

Name some organ-specific phagocytes and their locations.

Answer 12

Examples include Langerhans cells in the epidermis Kupffer cells (stellate macrophages) in the liver microglia in the brain as well as phagocytes in the spleen lymph nodes and lungs.

Question 13

What are fixed phagocytes and what is their role?

Answer 13

Fixed phagocytes are immobile cells located in the walls of organs and they remove pathogens from the lymph.

Question 14

According to Table 15.2 where are neutrophils found?

Answer 14

Neutrophils are found in the blood and all tissues.

Question 15

What process allows neutrophils and monocytes to enter tissues from the blood?

Answer 15

They squeeze through gaps in capillary walls in a process called extravasation or diapedesis.

Question 16

How are neutrophils and monocytes attracted to the site of infection?

Answer 16

They are attracted by a process called chemotaxis driven by cytokines called chemokines.

Question 17

Outline the steps of phagocytosis in tissues as described in the text.

Answer 17

1) The pathogen is engulfed by pseudopods 2) The vacuole containing the pathogen fuses with a lysosome 3) The pathogen is digested 4) Lysosomal enzymes may be released contributing to local inflammation.

Question 18

What role does the hypothalamus play in fever regulation?

Answer 18

The hypothalamus acts as a thermostat regulating fever by resetting the body temperature upward through prostaglandin PGE2.

Question 19

What are pyrogens and how do they induce fever?

Answer 19

Pyrogens are chemicals that provoke the release of prostaglandin PGE2 which resets the hypothalamic thermostat upward to cause fever.

Question 20

Provide examples of exogenous and endogenous pyrogens.

Answer 20

Exogenous pyrogens include lipopolysaccharides from some bacteria. Endogenous pyrogens include interleukin-1 (IL-1) interleukin-6 (IL-6) and tumor necrosis factor.

Question 21

What is adaptive immunity and what molecules mediate it?

Answer 21

Adaptive immunity is the acquired ability to defend against specific pathogens after exposure mediated by antigens and antibodies.

Question 22

What are antigens and what are antigenic determinant sites (epitopes)?

Answer 22

Antigens are cell surface molecules that stimulate the production of specific antibodies and combine with those antibodies. Large molecules may have several antigenic determinant sites (epitopes) that stimulate production and binding of antibodies.

Question 23

From where are lymphocytes derived and what organs do their stem cells seed?

Answer 23

Lymphocytes are derived from stem cells in the bone marrow which seed the thymus spleen and lymph nodes.

Question 24

Which lymphoid organs are considered primary lymphoid organs?

Answer 24

The bone marrow and thymus are considered primary lymphoid organs.

Question 25

What are T lymphocytes and what is their main function?

Answer 25

T lymphocytes are lymphocytes that seed the thymus and then populate the blood lymph nodes and spleen. They attack host cells infected with viruses or fungi.

Question 26

What is the main function of T lymphocytes in immunity?

Answer 26

T lymphocytes must be in close proximity to the victim cell to destroy it performing cell-mediated immunity. They do not produce antibodies.

Question 27

Where do B lymphocytes originate and what is their primary role?

Answer 27

B lymphocytes come directly from bone marrow (not the thymus) to seed other organs. They combat bacterial and some viral infections by secreting antibodies into blood and lymph which is called humoral or antibody-mediated immunity.

Question 28

How do T lymphocytes and B lymphocytes differ in their sites of processing and types of immunity?

Answer 28

T lymphocytes are processed in the thymus and provide cell-mediated immunity; B lymphocytes are processed in bone marrow and provide humoral immunity by secreting antibodies.

Question 29

What types of immunity are associated with B lymphocytes versus T lymphocytes?

Answer 29

B lymphocytes are associated with humoral immunity by secreting antibodies; T lymphocytes provide cell-mediated immunity through activated lymphocytes destroying infected cells.

Question 30

What are the key subpopulations of B and T lymphocytes?

Answer 30

B lymphocytes have memory B cells and plasma cells; T lymphocytes have cytotoxic T cells helper T cells and regulatory T cells.

Question 31

How do surface antibodies differ between B and T lymphocytes?

Answer 31

B lymphocytes have surface antibodies such as IgM or IgD; T lymphocytes do not have detectable surface antibodies but have receptors related to immunoglobulins.

Question 32

What roles do mast cells play during local inflammation?

Answer 32

Mast cells secrete heparin histamine serotonin protease enzymes vasoactive molecules pro-inflammatory cytokines prostaglandins leukotrienes tumor necrosis factor and other molecules that produce warmth swelling and pain and recruit more leukocytes.

Question 33

Describe the role of neutrophils in local inflammation.

Answer 33

Neutrophils kill microorganisms by phagocytosis release neutrophil extracellular traps (NETs) to trap pathogens undergo programmed cell death releasing protein-digesting enzymes causing pus and release granule proteins that attract monocytes.

Question 34

How do monocytes contribute to the resolution of inflammation?

Answer 34

Monocytes enlarge into macrophages phagocytose apoptotic neutrophils and release growth factors and other agents that end inflammation and promote tissue repair.

Question 35

What is the function of antibodies produced by B lymphocytes during inflammation?

Answer 35

Antibodies form antigen-antibody complexes that amplify phagocytosis by neutrophils and monocytes enhancing the immune response against pathogens.

Question 36

What causes redness and warmth during inflammation?

Answer 36

Redness and warmth during inflammation are caused by histamine-stimulated vasodilation.

Question 37

How does swelling (edema) occur during inflammation?

Answer 37

Swelling or edema occurs due to vasodilation and fluid buildup at the inflamed site.

Question 38

What causes pain during inflammation?

Answer 38

Pain during inflammation is caused by the release of Prostaglandin E2 (PGE2).

Question 39

What results in the formation of pus during inflammation?

Answer 39

Pus forms from phagocytosis and the accumulation of dead cells at the site of inflammation.

Question 40

What happens when a B lymphocyte is exposed to a specific antigen?

Answer 40

When exposed to a specific antigen a B lymphocyte is activated and undergoes multiple cell divisions (cloning). Some become memory cells for future infections while others become plasma cells that produce antibodies.

Question 41

Describe the structure of an antibody.

Answer 41

An antibody is a Y-shaped protein consisting of two long heavy (H) chains and two shorter light (L) chains. The bottom Fc region is constant while the top Fab region varies to allow antigen specificity.

Question 42

What are the main types of immunoglobulins and their functions?

Answer 42

- IgG: Main antibody in circulation; increases after immunization; secreted during secondary response.

Question 43

- IgA: Main antibody in external secretions like saliva and mother's milk.

Question 44

- IgE: Responsible for allergic symptoms in immediate hypersensitivity reactions.

Question 45

- IgM: Functions as antigen receptor on lymphocyte surfaces before immunization; secreted during primary response.

Question 46

- IgD: Functions as antigen receptor on lymphocyte surface before immunization; other functions unknown.

Question 47

How is the complement system activated?

Answer 47

The complement system is activated by binding antibodies to antigens (classic pathway) and by polysaccharides on bacterial membranes (alternative pathway).

Question 48

What roles does the complement system play after activation?

Answer 48

After activation the complement system labels targets for attack by phagocytes stimulates opsonization and destroys cells via complement fixation by attaching membrane attack proteins.

Question 49

What are the main components and functions of the complement proteins C1 to C9?

Answer 49

- C1: Recognition protein.

Question 50

- C2 C3 C4: Activators of the complement system.

Question 51

- C5 to C9: Attack cells by attaching to their membranes and destroying them through complement fixation.

Question 52

What distinguishes killer (cytotoxic) T lymphocytes and how do they destroy target cells?

Answer 52

Killer T lymphocytes have surface molecule CD8 and destroy body cells harboring foreign antigens by direct contact. They secrete perforins to create pores in the target cell membrane and granzymes to trigger apoptosis via caspase enzymes.

Question 53

What is meant by 'cell-mediated destruction' in the context of killer T lymphocytes?

Answer 53

Cell-mediated destruction means killer T cells must physically touch the target cell to destroy it.

Question 54

What types of cells or conditions can killer T lymphocytes target for destruction?

Answer 54

They can target cells infected by pathogens like viruses or fungi malignant cancer cells or transplanted cells.

Question 55

What is the role of helper T lymphocytes in the immune response?

Answer 55

Helper T lymphocytes which express CD4 enhance the ability of B lymphocytes to become plasma cells that secrete specific antibodies and improve immune responses.

Question 56

What are regulatory T lymphocytes (T reg) and what roles do they play in the immune system?

Answer 56

Regulatory T lymphocytes previously called suppressor T lymphocytes inhibit the response of B lymphocytes and killer T lymphocytes. A deficiency in their production can lead to autoimmune diseases and allergies.

Question 57

What are lymphokines and what functions do they serve in immune regulation?

Answer 57

Lymphokines are autocrine and paracrine regulators specific to lymphocytes. Many lymphokines stimulate B cell or cytotoxic T cell activity including interleukins produced by lymphocytes that regulate other lymphocytes.

Question 58

How do interleukins contribute to the regulation of the immune system?

Answer 58

Interleukins are cytokines produced by lymphocytes that regulate other lymphocytes. Different interleukins have distinct functions such as inducing proliferation and activation of T and B lymphocytes and promoting specific immune activities like production of IgE antibodies and activation of cytotoxic T cells.

Question 59

What are some of the specific functions of interleukins IL-1 IL-2 IL-4 and IL-5?

Answer 59

IL-1 induces proliferation and activation of T lymphocytes; IL-2 induces proliferation of activated T lymphocytes; IL-4 stimulates proliferation of activated B cells promotes production of IgE antibodies and increases activity of cytotoxic T cells; IL-5 induces activation of cytotoxic T cells and promotes eosinophil differentiation and chemotaxis.

Question 60

What is the role of antigen-presenting cells (APCs) in T cell activation?

Answer 60

APCs such as dendritic cells macrophages monocytes and B cells help T cells bind to antigens by engulfing protein antigens digesting them partially and displaying antigen fragments on their surface for T cells to recognize since T cell receptors cannot bind antigens directly.

Question 61

How do dendritic cells assist in immune defense and T cell activation?

Answer 61

Dendritic cells migrate to tissues where pathogens might enter engulf protein antigens digest them partially and display antigen fragments on their surface. This activates T cells which then divide to form effector and memory T cells.

Question 62

What are histocompatibility antigens and why are they important for organ transplants?

Answer 62

Histocompatibility antigens are molecules on the surface of all body cells (except mature red blood cells) coded by genes called the major histocompatibility complex (MHC) A B C D. Because many versions of these genes exist each person has a unique combination making MHC matching crucial for organ transplant compatibility.

Question 63

What types of cells produce Class 1 MHC molecules and what are their two main functions?

Answer 63

Class 1 MHC molecules are made by all cells except red blood cells (RBCs). They normally present self-antigens and can also present foreign antigens to activate cytotoxic T cells.

Question 64

Which cells produce Class 2 MHC molecules and how do these molecules function in the immune response?

Answer 64

Class 2 MHC molecules are made by antigen-presenting cells and B cells. They present foreign antigens together to helper T lymphocytes.

Question 65

What coreceptors are associated with Class 1 and Class 2 MHC molecules and which T cells do they correspond to?

Answer 65

Killer T cells have the CD8 coreceptor for MHC-1 molecules while helper T cells have the CD4 coreceptor for MHC-2 molecules.

Question 66

Describe the process of T cell response to a virus involving macrophages.

Answer 66

The virus is phagocytosed by macrophages or dendritic cells; viral foreign antigens are moved to the surface of the presenter cell and form a complex with MHC-2 molecules which activates helper T cells.

Question 67

What are the key substances secreted by helper T cells during a viral response and what effects do they have?

Answer 67

Helper T cells secrete gamma interferon to promote macrophage activity secrete interleukin-2 to activate cytotoxic T cell mitosis and activate B cells by binding to their MHC-2 to induce mitosis and conversion to plasma cells that produce antibodies and memory B cells.

Question 68

What are allergies and how are they classified in terms of immune response?

Answer 68

Allergies are abnormal responses to allergens (antigens) also called hypersensitivity. They are classified into two types: immediate hypersensitivity and delayed hypersensitivity.

Question 69

What characterizes immediate hypersensitivity reactions?

Answer 69

Immediate hypersensitivity is an abnormal B cell response to allergens with effects occurring seconds to minutes after exposure. It is caused by foods bee stings pollen etc. leading to allergic rhinitis conjunctivitis allergic asthma atopic dermatitis and food allergies. Plasma cells secrete IgE antibodies instead of IgG.

Question 70

How do IgE antibodies function in immediate hypersensitivity?

Answer 70

IgE antibodies do not circulate in the blood but attach to mast cells and basophils. Upon re-exposure to the same allergen these cells release histamine leukotrienes and prostaglandin D producing allergy symptoms.

Question 71

What distinguishes delayed hypersensitivity from immediate hypersensitivity?

Answer 71

Delayed hypersensitivity is an abnormal T cell response producing symptoms hours to days after exposure. The symptoms are caused by secretion of lymphokines not histamine making antihistamines ineffective. An example is contact dermatitis caused by poison oak ivy or sumac.