The Immune System
Chapter 43
Overview
Innate vs. Acquired Immunity
 Innate Immunity:
 Present from the time of birth
 Nonspecific
 External barriers, Mucous membranes, macrophages
 Acquired Immunity:
 Highly specific
 Humoral response (antibodies)
 Cell-mediated response (cytotoxic lymphocytes)
Innate vs. Acquired Immunity
43 ~1 Innate Immunity
External Defenses:
 Skin
 Acidic pH
 Physical barrier
 Mucous membranes
 Traps microbes
 Antimicobial Proteins - Lysozyme
 Enzyme that destroys bacteria
Internal Cellular & Chemical
Defenses
 Phagocytosis
 The ingestion of invading microorganisms by certain types
of white blood cells
 4 white blood cells are phagocytic
 Neutrophils
 Macrophages
 Eosinophils
 Dendritic cells
Phagocytosis
Lymphatic system
Internal Cellular & Chemical
Defenses
 Antimicrobial Proteins
 Attack microbes
 Lysozyme
 Complement system – 30 proteins that activate when
microbes invade
 Interferon – protection against viral infection by limiting
cell to cell reproduction
Internal Cellular & Chemical
Defenses
 Inflammatory Response – damage to tissue by physical
injury
 Histamine causes increased blood flow to the inured site
(redness & heat = inflammation)
 Help deliver antimicrobial proteins and clotting elements
to the injured site
Inflammatory Response
Internal Cellular & Chemical
Defenses
 Natural Killer Cells
 Patrol the body and attack virus-infected body cells and
cancer cells
 Apoptosis – NK cells release chemicals that lead to death of
the cell by apoptosis (programmed cell death)
43 ~ 2 Acquired Immunity
 Activates Lymphocytes
 Antigen – any foreign molecule that is specifically
recognized by lymphocytes and elicits a response from
them
 2 main types of lymphocytes
 B lymphocytes (B cells)
 T lymphocytes (T cells)
 Both circulate through the blood and lymph and are
concentrated in the spleen, lymph nodes, and other
lymphoid tissue
Lymphocyte development
 Originate from pluripotent stem cells in the bone
marrow
 T cells develop in the Thymus
 B cells remain in bone marrow and complete maturation
there
Lymphocyte development
Primary vs. Secondary Immune
response
 Primary immune response: occurs the first time the
body is exposed to a particular antigen
 Peaks about 10-17 days after exposure
 Secondary Immune response: occurs after a second
exposure to the same antigen
 Faster
 Greater magnitude
 More prolonged
Primary vs. Secondary Immune
response
43.3 ~ Humoral & Cell-mediated
response
 Humoral immune response – involves the activation and
clonal selection of B cells, resulting in production of
secreted antibodies that circulate in the blood and
lymph
 Cell-mediated immune response – involves the
activation and clonal selection of cytotoxic T cells which
directly destroy certain target cells.
Humoral vs. cell-mediated
immune response
43.4 ~ Distinguishing self from
non-self
 Blood groups and transfusions
 Tissue and organ transplants
Blood groups & Transfusions
 A, B, AB, and O blood groups
 A red blood cells have A antigens on their surface and
make antibodies against the B antigen.
 Transfusion reaction – chills, fever, shock and kidney
malfunction
 AB = universal recipient
 O = universal donor
 Rh negative mother carries a fetus that is Rh positive
mother mounts a humoral response. Danger occurs in
subsequent pregnancies with Rh positive fetus.
Tissue & Organ Transplants
 A rejection reaction is mounted in most graft and
transplant recipients because molecules are foreign.
 No danger of rejection if the donor and recipient are
identical twins or if tissue is grafted from another part
of the same person’s body.
43.5 ~ Immune system Diseases
 Allergies – are exaggerated (hypersensitive) responses to
certain antigens called allergens
 Typical allergy symptoms: sneezing, runny nose, tearing
eyes, and smooth muscle contractions
 Anaphylactic shock – acute allergic response leads to a
whole-body life-threatening reactions. Responses to
bee venom, penicillin, peanuts, fish
 Epinephrine (epipen) counteracts this allergic response
 Autoimmune Diseases: The immune system loses
tolerance for self and turns against certain molecules
 Lupus – skin rashes, fever, arthritis, and kidney dysfunction
 Rheumatoid arthritis – painful inflammation of cartilage
and bond of joints
 Multiple Sclerosis – T cells enter CS and destroy myeline
sheath
 Arise from some failure in immune system regulation
 Immunodeficiency Diseases: The inability of the immune
system to protect the body from pathogens or cancer
cells that it should normally
 Inborn (SCID) vs. acquired (AIDS)
 Stress & the Immune System: Healthy immune function
depends on both the endocrine system and nervous
system
 Hormones secreted by the adrenal glands during stress
affect the # of white blood cells and can suppress the
immune system
 Acquired Immunodeficiency Syndrome (AIDS): Highly
susceptible to infections (Pneumonia, bronchitis)
 Loss of helper T cells both humoral and cell-mediated
are imparied
 Results from infection by HIV (retrovirus)