HUMAN BIOLOGY

ImmunIty and dIsease 175

section 9.5 Adaptive defenses
attack specific pathogens. They combat a
great diversity of antigens, and generate
memory T and B cells that provide
extended immunity. When B cells and
T cells recognize an antigen, they are
activated and multiply to form large
populations of identical cells.
Plasma cells are effector B cells that make antibodies
which bind specific antigens and flag them to be destroyed by
phagocytes or other defender cells.
T cells provide cell-mediated immunity. T cells recognize
combinations of antigen fragments and MHC self markers.
These complexes are produced by antigen-presenting cells.
Cytotoxic T cells are effectors that attack intruders directly.
Helper T cells release cytokines that mobilize and strengthen
defense responses.

section 9.6 Antibodies target

pathogens outside cells. In the antibody-

mediated response, plasma cells secrete

large numbers of antibodies that circulate

in the bloodstream. Antibodies are

proteins called immunoglobulins. Each

binds one kind of antigen. The five

classes of antibodies are IgG, IgD, IgE,

IgA, and IgM.

section 9.7 Cell-mediated

responses destroy infected cells, cancer

cells, and cells of tissue or organ

transplants. Cytotoxic T cells secrete

chemicals that can trigger apoptosis

(programmed cell death) in an

invading cell.

section 9.8 Vaccination provokes an

active immune response, including the

production of memory cells. Injections

of anti bodies help fight infection by

conferring short-term passive immunity.

Monoclonal antibodies are used in medical

research, testing, and the treatment of

various diseases.

section 9.9 An allergy is an immune

response to a substance that normally is

harmless. Anaphylactic shock is the most

severe allergic response. In autoimmune

disorders, the immune system’s weapons

are unleashed against normal body cell

or proteins. In immune deficiency, the

immune system is weakened (as by HIV)

or completely absent.

rEviEW QUEstions

1. While you’re jogging in the surf, your toes land on a jellyfish.
   Soon the bottoms of your toes are swollen, red, and warm to
   the touch. Using the following diagram as a guide, describe
   how these signs of inflammation came about.

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2. Distinguish between
   a. neutrophil and macrophage
   b. cytotoxic T cell and natural killer cell
   c. effector cell and memory cell
   d. antigen and antibody


3. What is the difference between innate immunity and
   adaptive immunity?


4. What is the difference between an allergy and an
   autoimmune response?

sELf-QUiz Answers in Appendix VI

1. are barriers to pathogens at body surfaces.
   a. Intact skin and mucous membranes
   b. Tears, saliva, and gastric fluid
   c. Resident bacteria
   d. All are correct


2. Complement proteins function in defense by.
   a. neutralizing toxins
   b. enhancing resident bacteria
   c. promoting inflammation
   d. forming pores that cause pathogens to disintegrate
   e. both a and b
   f. both c and d


3. are molecules that lymphocytes recognize as
   foreign and that elicit an immune response.
   a. Interleukins d. Antigens
   b. Antibodies e. Histamines
   c. Immunoglobulins


4. Another term for antibodies is ; there are
   classes of these molecules.
   a. B cells; three
   b. immunoglobulins; three
   c. B cells; five
   d. immunoglobulins; five


5. Antibody-mediated responses work best against.
   a. pathogens inside cells d. both b and c
   b. pathogens outside cells e. all are correct
   c. toxins


6. Cell-mediated responses work best against.
   a. pathogens inside cells d. both b and c
   b. pathogens outside cells e. all are correct
   c. toxins

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