Download 26.1 Organs, Tissues, and Cells of the Immune System (cont.)

Essentials of Biology
Sylvia S. Mader
Chapter 26
Lecture Outline
Prepared by: Dr. Stephen Ebbs
Southern Illinois University Carbondale
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
26.1 Organs, Tissues, and Cells
of the Immune System
• The immune system protects the body by
fighting infection and cancer.
• The immune systems consists of several
lymphatic organs.
– Red bone marrow
– Thymus gland
– Lymph nodes
– Spleen
26.1 Organs, Tissues, and Cells
of the Immune System (cont.)
• There are also specialized lymphatic
tissues.
– Tonsils
– Appendix
• Specialized cells also contribute to the
immune system.
26.1 Organs, Tissues, and Cells
of the Immune System (cont.)
26.1 Organs, Tissues, and Cells
of the Immune System (cont.)
26.1 Organs, Tissues, and Cells
of the Immune System (cont.)
• These various organs, tissues, and cells provide
for immunity, which is the ability to react to
antigens.
• Antigens are proteins that are foreign to the
organism.
• Antibodies are specialized proteins produced by
an organism that bind to specific antigens.
Lymphatic Organs
• Each lymphatic organ has a specific
function in immunity.
• All lymphatic organs contains one or more
lymphocytes, one category of immunocells
that protect the body.
Red Bone Marrow
• The red bone marrow produces all the
different types of red blood cells.
• There are several types of lymphocytes
produced by the red bone marrow.
– B lymphocytes, also called B cells
– T lymphocytes, also called T cells
Thymus Gland
• Immature T cells produced by the red
bone marrow migrate to the thymus where
they complete their maturation.
• The thymus produces hormones that are
thought to help T cells mature.
• The thymus selectively release T cells that
have matured properly.
Lymph Nodes
• The lymph nodes filter the lymphatic fluid
to remove antigens and pathogens.
• Antigens and pathogens are removed by
the phagocytic macrophages.
• Lymphocytes in the lymph nodes all
contribute to the defense against antigens
and pathogens in the lymphatic fluid.
Spleen
• The spleen has two areas that contribute
to immunity.
– Red pulp
– White pulp
• The red pulp filters pathogens and debris
with the help of macrophages.
• The white pulp contains lymphocytes that
fight pathogens and cancer.
26.2 Nonspecific Defenses
• The body has a variety of nonspecific
defenses that help protect the body from
infection.
– Barriers to entry
– The inflammatory response
– Natural killer cells
Barriers to Entry
• There are two primary barriers that
prevent entry of pathogens into the body.
– The skin
– The mucous membranes
• In addition to mechanically blocking
pathogen entry, the skin has oil glands
secrete chemicals to counter pathogens.
Barriers to Entry (cont.)
The Inflammatory Response
• Any damage to the body’s tissues trigger events
of the inflammatory response.
–
–
–
–
Reddening
An increase in temperature
Swelling
Pain
• The inflammatory response also involves three
cell types.
– Mast cells
– Neutrophils
– Macrophages
The Inflammatory Response (cont.)
• The mast cells release chemicals such as
histamine to increase the blood flow through the
capillaries.
• This increased blood flow contributes to the
redness, swelling, and warmth.
• Because of the swelling, nerve receptors are
triggered to create the sensation of pain.
The Inflammatory Response (cont.)
• Neutrophils are phagocytic white blood
cells that migrate to the site of injury.
• Macrophages have several roles.
– These cells are phagocytic.
– These cells release chemicals that trigger
white blood cell production in the red marrow.
The Inflammatory Response (cont.)
The Inflammatory Response (cont.)
The Complement System
• The complement system consists of a
variety of blood plasma proteins.
• When activated by the presence of
pathogens, these proteins amplify the
immune response.
• Complement proteins also form a
membrane attack complex that contributes
to the lysis of pathogens.
The Complement System (cont.)
Natural Killer Cells
• Natural killer cells are non-specific
lymphocytes that kill virus-infected and
cancerous cells.
• Natural killer cells kills cells that lack
surface proteins identifying them as “self”.
26.3 Specific Defenses
• Specific defenses are used in immunity
when the nonspecific defenses fail to halt
a pathogen or infection.
• One advantage of the specific defenses is
that they can provide a “memory” of the
infection.
B Cells and the Antibody Response
• The B-cell receptor (BCR) on the surface of B
cells allows for the recognition of and binding to
specific antigens.
• The binding of the BCR to an antigen activates
the B cell.
• Activated B cells undergo cell division to
produce two special types of B cells.
– Plasma B cells
– Memory B cells
B Cells and the Antibody
Response (cont.)
• Plasma cells are responsible for the mass
production of antibodies for the antigen.
• The antibodies are released into the
bloodstream to help the body identify the
antigen within the body.
B Cells and the Antibody
Response (cont.)
B Cells and the Antibody
Response (cont.)
• Memory B cells are retained within the
body for an extended period of time.
• The memory B cells allow the body to
mount an immune response more quickly
if the antigen is perceived again.
B Cells and the Antibody
Response (cont.)
The Function of Antibodies
• Recall that antibodies are immunoglobulin
proteins that recognize specific antigens and
forms an antibody-antigen complex.
• The formation of an antibody-antigen complex
can mark an antigen for destruction by
neutrophils or macrophages.
• The antibody-antigen complex may also act as
complement to amplify the immune response.
The Function of Antibodies
(cont.)
The Function of Antibodies
(cont.)
• The proteins that determine blood type are
also a type of antigen on the surface of red
blood cells.
• Type A, B, or AB blood results from the
presence of the A and/or B antigen.
• Type O blood occurs when the red blood
cells lack the A or B antigen.
The Function of Antibodies
(cont.)
• The blood also contains antibodies to the red
blood cell antigens that are not present.
• If incompatible types of blood are mixed,
antibody-antigen complexes can form when
agglutination occurs.
• This clumping of red blood cells restricts blood
flow and can ultimately be fatal.
The Function of Antibodies
(cont.)
T Cells and the Cellular
Response
• The mature T cells that leave the thymus gland
have unique T-cell receptors (TCR).
• These receptors only recognize an antigen when
an antigen-presenting complex (APC) of a
macrophage presents the antigen to the TCR.
• The presentation of the antigen by the APC
activates the T cell.
T Cells and the Cellular
Response (cont.)
• An activated T cell undergoes cell division
to produce two types of T cells.
– Cytotoxic T cells
– Helper T cells
T Cells and the Cellular
Response (cont.)
Types of T Cells
• Cytotoxic T cells release a protein called perforin
to create a pore in the surface of infected cells.
• Cytotoxic T cells also release granzymes that
then trigger the infected cell to undergo
apoptosis (self-destruct).
• Cytotoxic T cells are responsible for the
response to virus-infected and cancerous cells.
Types of T Cells (cont.)
Types of T Cells (cont.)
Types of T Cells (cont.)
• Helper T cells contribute to immunity by
secreting cytokines.
• Cytokines are chemicals that stimulate the
immunocells, particularly the B cells.
Tissue Rejection
• The immune system may also be important
when an individual receives an organ transplant.
• Rejection occurs when cytotoxic T cells and
antibodies respond to the transplanted tissues
as if they were pathogens.
• Tissue rejection can be minimized in two ways.
– Transplanting tissues with similar surface antigens to
the recipient.
– Administering immunosuppressing drugs.
26.4 Immunizations
• Vaccines and immunizations are used to
protect individuals from specific diseases.
• The introduction of a vaccine promotes an
active immune response and the formation
of memory B cells.
• This acquired immunity prepares the body
to respond quickly if the disease is
perceived again.
26.4 Immunizations (cont.)
26.4 Immunizations (cont.)
• Temporary immunity can also be imposed
through the introduction of specific
prepared antibodies to the body.
• This immunity is passive immunity.
• Another example of passive immunity is
the transfer of antibodies from mother to
child during breast-feeding.
26.5 Immune System Problems
• The immune system itself can malfunction
and become harmful to the body.
• This can occur when the immune system
fails to distinguish “self” from “nonself”.
Allergies
• Allergies are a hypersensitive response to
antigens called allergens.
• An immediate allergic response occurs
within seconds of exposure to an allergen
and may be life-threatening.
• The immediate allergic response involves
the release of histamine from mast cells.
Allergies (cont.)
• Delayed allergic responses occur at point
after the exposure to the allergen.
• The delayed response is probably due to
the cytokines secreted by immunocells.
Allergies (cont.)
Autoimmune Diseases
• Autoimmune diseases
occur when cytotoxic T
cells attack the body’s
own cells.
• There are several
autoimmune diseases.
– Multiple sclerosis
– Systemic lupus
– Rheumatoid arthritis
AIDS
• Acquired immunodeficiency syndrome (AIDS)
occurs when the body loses the ability to fight
infection.
• AIDS is caused by the human immunodeficiency
virus (HIV).
• AIDS gradually destroys the body’s helper T cell
population, leading to susceptibility to secondary
infections.
AIDS (cont.)