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10.1 The Body¶s Lines of DefenceDavid Vetter (1971-1984)Born with severecombinedimmunodeficiency(SCID)SCID is an X-linkeddisorder, and David¶smother was a carrier Ten seconds after birth,David was placed in aplastic bubble
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David Vetter
David needed agerm-freeenvironment, so hehad to be inside hisbubble for 12 yearsDoctors hoped to cureSCID using a bondmarrow transplant
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The Bone Marrow Transplant
October 21, 1983, David received a bonemarrow transplant from his sister,
KatherineThe marrow contained the Epstein-Barr virus that causes mononucleosis
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Medical Ethics
While knowing that David would have tolive life in a bubble, doctors encouraged
his mother to go through with thepregnancy. Some people have said that inthis situation, it would have been better toterminate the pregnancy.What do you think?
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What was gained?
Doctors now knowthat SCID can betreated within threemonths of birth withbone marrowscreened for pathogens
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The Three Lines of Defense
The first and secondlines of defense of thehuman body arenonspecific immuneresponsesThe third line of defense, you immunesystem, reacts inspecialized ways for various invaders
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The First Line of DefenseMostly physicalSkin and mucousmembranes protect your body
Acidic secretions keepskin at pH of 3-5Skin has acidic secretionsthat inhibit the growth of microbes
Lysozyme, anantimicrobial enzyme, issecreted in tears, saliva,mucous and sweat.
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R espiratory and Digestive System
The respiratory passage islined with mucousCilia also lines the respiratorypassage
There is mucous in therespiratory passage that trapsinvading microbes and other foreign debris with the cilia.Acids in the stomach andprotein digesting enzymes
destroy most of the invadingmicrobes carried into the bodywith food.
Immune SystemOverview: Goals
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The Second Line of Defense
Mobilized if aninvader resides insidethe body
Leukocytes (whiteblood cells), engulf invading microbes, or produce antibodies
Unlike red blood cells,white blood cells havea nucleus
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Leukocytesalso called white blood cellsare large opaque blood cellsthat engulf invading microbes.
They can also produceantibodies. ± They have a nucleus (so
different from red blood cells) ± The size of the nucleus and
the types of granules that canbe found inside of them canbe used to classify them intodifferent classes of leukocytes.
Granulocytes: havecytoplasmic granules and aremade in the bone marrow.Agranulocytes: do not have agranular cytoplasm and arealso made in the bonemarrow, but then modified inthe lymph nodes.
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P hagocytosis
Non-specific defensemechanisms relymainly on
phagocytosisMonocytes migratefrom the blood andinto the tissues
Macrophages extendpseudopods that gripthe invading microbe
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NeutrophilsAttracted to chemical signals emitted bydamage microbesChemotaxis: A process where theneutrophils exit the capillaries and movetoward the damaged tissueLysosomal enzymes digest the microbeand the leukocyte
The remaining fragments of protein, deadwhite blood cells and the digestedmicrobes are called p us
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P hysical Injury
Tissue damage initiates alocalized inflammatoryresponse ± It is a nonspecific immune
response that results inswelling, redness, heat,and pain.
± P us and inflammation aresigns that the second lineof defence has been atwork.
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System Wide Defense
Injured cells emitchemicals thatstimulate theproduction of phagocytic whiteblood cells, red bloodcells and lymphocytesfrom the bone marrow
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Fever is another example of the body¶sresponse to infection. ± When you have infectious organisms in your
body, neutrophils and macrophages digestthe invaders and release chemicals into the
bloodstream ± When the chemicals reach the hypothalamus,
they reset your body temperature to 40 r C inorder to make it difficult for the bacteria to
survive.
