THE BODY’S DEFENSE CHAPTER 43
Dec 29, 2015
Immunity• Invertebrates have nonspecific
systems• Plants have molecular recognition of
pathways to defend against pathogens; leads to destruction of infected cells
• Vertebrates have nonspecific and nonheritable defense systems
• Mammals have nonspecific, humoral and cell mediated.
Figure 43.2 First-line respiratory defenses. Inside the lining of the trachea.
Yellow cells are ciliated. Orange cells secrete mucus.
•Innate immunity is present before any exposure to pathogens and is effective from the time of birth
• It involves nonspecific responses to pathogens
• Innate immunity consists of external barriers plus internal cellular and chemical defenses
•Acquired immunity, or adaptive immunity, develops after exposure to agents such as microbes, toxins, or other foreign substances
• It involves a very specific response to pathogens
CELLS:Nonspecific
•Neutrophils - engulf microbes (phagocytosis); self-destruct after destroy microbes
•Macrophages - can migrate into tissues and engulf microbes
•Esinophils - destroy parasitic worms
•Natural killer cells - destroy viral-infected cells
Figure 43.x1 Anabaena (a blue-green algae that makes a toxin, which causes cell death)
phagocytosed by a human neutrophil
Anabaena
INFLAMMATORY RESPONSE
•Arterioles dilate to increase blood flow to damaged area
• Increased WBC in damaged area
•Histamine and prostaglandins released to dilate arterioles
•Chemokines - chemical signals for cells to follow
Fig. 43-8-3
Pathogen Splinter
Macrophage
Mast cell
Chemicalsignals
Capillary
Phagocytic cellRed blood cells
Fluid
Phagocytosis
SPECIFIC DEFENSE
•Response is to a specific microbe
•Antigen - foreign molecule•Antibody - proteins made to
attach to specific antigens
CELLS:Specific
•B lymphocytes - develop in bone marrow; differentiate into plasma cells which secrete antibodies; also make memory cells
•T lymphocytes - develop in thymus; activate B cells and other WBC; also make memory cells
•Primary immune response - first exposure; 10 - 17 days; make antibodies
•Secondary immune response - already been exposed; 2 - 7 days; memory cells make antibodies quickly
TOLERANCE FOR SELF•Major histocompatibility complex (MHC) on cells–Class I MHC on all nucleated cells
–Class II MHC on macrophages, B cells and activated T cells
–Biochemical fingerprint–As your cells develop, if fingerprint is wrong then cell death occurs
–MHC molecules cradle foreign antigens. They present the antigen to other cells.•MHC I presents antigens to Cytotoxic T cells which kill bad cells
•MHC II presents antigens to Helper T cells
–Cells that present antigens are called antigen presenting cells (APCs). These include macrophages and B cells.
HUMORAL VS. CELL MEDIATED IMMUNITY
•Humoral - B cells activated by free antigens (free bacteria, toxins, viruses)
•Cell mediated - depends on T cells; active against cells infected with viruses and bacteria; as well as free fungi, protozoa, and worms
Fig. 43-16
Humoral (antibody-mediated) immune response
B cell
Plasma cells
Cell-mediated immune response
Key
Stimulates
Gives rise to
+
+
++
+
+
+Memory B cells
Antigen (1st exposure)
Engulfed by
Antigen-presenting cell
MemoryHelper T cells
Helper T cell Cytotoxic T cell
MemoryCytotoxic T cells
ActiveCytotoxic T cells
Antigen (2nd exposure)
Secretedantibodies
Defend against extracellular pathogens by binding to antigens,thereby neutralizing pathogens or making them better targetsfor phagocytes and complement proteins.
Defend against intracellular pathogensand cancer by binding to and lysing theinfected cells or cancer cells.
+
+ +
Immune System Players•Antigen presenting cells (APC) include B cells and macrophages
•Present antigen on class II MHC
•T helper cell (Th) binds to MHC II with antigen
•CD4 on Th cell holds APC cell and Th cell together
ANTIBODY PRODUCTION
•T-dependent antigens - B cell must be activated by Th cell; most protein antigens
•T-independent antigens - directly stimulate B cells to make antibodies; mostly polysaccharide antigens
ANITBODY MEDIATED DISPOSAL OF ANITGEN
•Opsonization - many antibodies bound to antigen enhance macrophage phagocytosis
•Agglutination - antibodies attach to many antigens; clumping them together to enhance phagocytosis
ACTIVE IMMUNITY
•Depends on response of infected person’s immune system
•May be artificially induced by vaccinations
PASSIVE IMMUNITY
•Antibodies transferred from one individual to another
•Some antibodies can move across placenta to baby in pregnant women
•Nursing
HEALTH AND DISEASE•Review ABO blood types
and Rh•MHC causes tissue and
organ rejections•In bone marrow transplants,
donated marrow (with WBC) will react against recipient
•Allergies - overproduction of certain antibodies causes histamine to be released–Runny nose–Teary eyes–Smooth muscle contractions = hard breathing
•Anaphylactic shock - life-threatening reaction; abrupt dilation of arteries causes serious drop in blood pressure
•Autoimmune diseases - attack own body–Lupus, rheumatoid arthritis, MS
• Immunodeficiency Diseases –Severe combined immunodeficiency (SCID), Hodgkin’s
•AIDS - acquired immunodeficiency syndrome–Two major strain: HIV I and HIV II
–Bind to CD4 and therefore Th cells
–Insert its RNA and reverse transcriptase makes viral DNA that is inserted into host’s DNA
–Exists as provirus so antibodies can’t get rid of it easily
–Mutates often
–May cause Th cell death
–HIV positive = presence of HIV antibodies