this is chapter 22,module 2-- innate and adaptive immune systems. the learning objectivesof this module are, one, distinguish betweeninnate, or nonspecific, and adaptive, orspecific, defenses. two, define adaptivespecific defenses. three, describethe body's innate, or nonspecific, defenses. and four, distinguish betweenpassive and active, and natural
and induced immunity. the lymphatic systemand other body defenses provide resistance tofight infection, illness, and disease. there are two categoriesof defenses-- innate, or nonspecific defenses, andadaptive, or specific defenses. innate or nonspecific defensesalways work the same way, and work against anytype of invading agent. adaptive or specificdefenses protect
against specificpathogens, and they rely on the activitiesof lymphocytes. adaptive defenses onlydevelop after exposure to the environmental hazard. there are seven major categoriesof innate or nonspecific defenses-- physicalbarriers, phagocytes, immunological surveillance,interferons, complement, inflammatoryresponse, and fever. physical barriers keep hazardousorganisms and material outside
of the body. they include barrierslike the skin and hair, and secretions from sweatglands, mucus, and urine that help flush away materials. these secretions includeenzymes, antibodies, salt, and stomach fluid that killsor inhibits microorganisms. the other innatedefenses involve cells. phagycytes engulfpathogens and cell debris. phagycytes include cells suchas macrophages, both free
and fixed, neutrophils,eosinophils, and monocytes. some macrophages aregiven special names in certain areas of the body. microglia are found in thecentral nervous system, whereas kuppfer cells are foundin the sinusoids of the liver. and alveolar macrophagesare found in the lungs. all macrophages movethrough capillary walls as they are attracted tochemicals in the surrounding fluids, called chemotaxis.
phagocytosis occurs when thepyagocyte attaches to a target and surrounds it with its cellmembrane forming a vesicle. immunological surveillanceinvolves the natural killer cells, which are t cells. these nk cells destroy abnormalcells in the peripheral tissues by shooting chemicalscalled perforins at them, that penetrate the cellmembrane of the abnormal cells and cause the pathogen to lyse. natural killer cellsattack any abnormal cell,
including cancer cells andcells infected with viruses. interferons are chemicalsreleased by activated body cells, such aslymphocytes, macrophages, and virus-infected cells. the interferon chemicalsact as messengers to coordinate the defenseagainst viral infections to slow down the spreadof viral infections. the complement systemis a defense system that consists ofcirculating proteins.
the plasma contains 11special proteins called complements that formthis complement system. these proteins worktogether in cascades, where one proteinactivates the next, which then activates the next. these proteinsassist the antibodies in destruction of pathogensby binding to the pathogen and causing them to lice. another body defenseis inflammation.
inflammation is triggeredby any stimulus that kills cells or injures tissues. the main signs andsymptoms of inflammation are redness, swelling,heat, and pain. inflammation temporarilyprovides a barrier against pathogens,retards the spread of pathogen movementinto surrounding areas, and mobilizes local and systemdefenses against pathogens. cells called mast cellscaused a localized response
in the tissues to limitthe spread of an injury or infection. they do so by increasingblood flow and permiability of capillaries, activatingphagocytes, activating complement, increasing clottingto wall off the region, increasing the temperatureregionally, and activating the adaptive immune system. mast cells are very similarto the basophil in that they release histamineand heparin, but they
play more of a role againstpathogens then basphils do. also, basophils arefound in the blood, whereas mast cells arefound in the tissues. fever is anothernonspecific body defense. fever is an elevationof body temperature above 99 degrees fahrenheit inresponse to pyrogens regions. pyrogens are any materialthat causes the hypothalamus to raise body temperature,and include pathogens, toxins, or antibody complexes.
fever accelerates tissuemetabolism and activity of body defenses, as wellas inhibits the multiplying of pathogens. adaptive or specificdefenses are different fromnonspecific defenses because this is a responseto a specific antigen. and the coordinated actions of tcells and b cells are required. the innate, nonspecificdefenses we looked at are all present at birth,whereas the adaptive
or specific defenses areacquired after birth. adaptive immunity can beeither active or passive. active immunity means antibodiesdevelop after exposure to an antigen, whereas passiveimmunity means antibodies are transferred fromone person to another, and the body is not requiredto developing antibodies on its own. active immunity can be naturallyacquired through a person receiving exposure topathogens in the environment,
such as one person havingthe chicken pox virus and spreading itto another person. or, active immunity canbe artificially induced, where a health professionaldelivers pathogens in the form of a vaccine. passive immunity canbe naturally acquired, such as a mothernursing her baby and deliveringantibodies directly to the baby through breast milk.
or, passive immunity canbe artificially induced through the injectionof antibodies, such as with the person whowas bit by a poisonous snake. this person doesn't havetime to wait for the body to respond to makeantibodies, so antibodies must be injected to savetheir lives from the poisonous antigens in snake venom. adaptive immunityhas four properties-- specificity, versatility,memory, and tolerance.
specificity meansthat each t or b cell responds to a specificantigen and ignores all others. versatility meansthe body produces many types oflymphocytes, and each type fights a differenttype of antigen. each active lymphocytecan clone itself to fight the specific antigen. memory is a property wheresome active lymphocytes, called memory cells, stayin circulation
to provide immunityagainst another invasion by the same pathogenin the future. tolerance is the body'simmune system's ability to ignore normal antigens,such as self-antigens. in other words, thebody is programmed not to attack its own normal cells.
No comments:
Post a Comment