The immune system defends the body - PDF document

1 MATERIALS MAIN IDEA AND DETAILS The immune system has specialized lls called white blood cells thatnize foreign materials in the body and respond.The number ofwhite blood cells in the blood can increase during an immuneesponse.These cells travel through the circulatory system and thelymphatic system to an injured or infected area ofthe body.Whiteblood cells leave the blood vessels and travel into the damaged tissue,where the immune response takes place.The Lymphatic SystemThe lymphatic system transports pathogen-fighting white blood lls throughout the body,much as the circulatory system does.The lymphatic system carries lymph,and the circulatory system carries blood.Both fluids transport similar materials,such as whiteblood cells.mph is the fluid left in the tissues by the circulatory system.Itmoves through lymph vessels,which are similar to veins.However,thelymphatic system has no pump like the heart to move fluid.Lymphdrifts through the lymph vessels when your skeletal muscles contractor when your body changes position.As it moves,it passes throughlymph nodes,which filter out pathogens and store white blood cellsand antibodies.Because lymph nodes filter out pathogens,infectionsare often fought in your lymph nodes,causing them to swell whenCheck Your ReadingThe immune system responds to attack.Certain illnesses can cause symptoms such as coughing,sneezing,andfever.These symptoms make you uncomfortable when you are sick.t in fact,most symptoms are the result ofthe immune systemÕsesponse to foreign materials in the body.The immune system responds in two ways.The white blood cellsthat first respond to the site ofinjury or infection attack foreign terialsin a nonspecific response.Some ofthese cells attack foreignterialsand produce chemicals that help other white blood cells workbetter.The second part ofthe response is very specific to the types ofpathogens invading the body.These white blood cells produce antibod-ies specific to each pathogen and provide your body with immunity. RESOURCE CENTERCLASSZONE.COM Learn more about thelymphatic system. 8750
The mast cell above is animportant part of the ansport and Protectionelling,redness,and heat are some ofthe symptoms that tell youthat a cut or scrape has become infected by foreign materials.They areall signs ofinflammation,your bodyÕs first defense reaction againstinjuries and infections.en tissue becomes irritated or damaged,it releases largeamounts ofhistamine (HIHS-tuh-meen).Histamine raises the tem-perature ofthe tissues and increases blood flow to the area.Increasedblood flow,which makes the injured area appear red,allows antibod-ies and white blood cells to arrive more quickly for battle.Highermperatures improve the speed and power ofwhite blood cells.Somepathogens cannot tolerate heat,so they grow weaker.The swellingcaused by the production ofhistamine can be a small price to pay forthis chemicalÕs important work.en a foreign material affects more than one area ofyour body,many tissues produce histamine.As a result,the temperature ofyourwhole body rises.Any temperature above 37 degrees Celsius (98.6¡F)is considered a fever,but only temperatures hot enough to damage tis-sues are dangerous.Trying to lower a high fever with medication isadvisable in order to avoid tissue damage.When you have a smallfever,lowering your body temperature might make you more com-fortable,but it will not affect how long you stay sick.Check Your Reading the injury. Specific immune responses differ from nonspecific responses in twoways.First,specific responses are triggered by antigens.An isa chemical marker on a cellÕs surface that indicates whether the cell is from your body or is a foreign material.When the body detects aforeign antigen,specific immune responses occur.Second,a specificimmune response provides protection from future exposure to thesame material.Three major types ofwhite blood cellsÑphagocytes,T cells,and B cellsÑfunction together in a specific response.Phagocytes ingest and break down foreignmaterials.Small pieces ofthe foreign materials are incorporated intothe surface ofthe phagocyteÕs cell membrane.These foreign particlesntain antigens that are detected as foreign by T cells.The T cells antigen foreignpresenting presenting phagocyte. 1 T cellT cellT cellT cell Some T cells signal to make antibodies to fight 3 Some T cellsdestroycells that have beeninfected by the pathogen. 3 When pathogens invade the body, several types ofattack foreign materials. the antigens,mark- 4 apidly. 2 5500
T cell T cell r your body has destroyed a specificpathogen,B cells that fight that pathogenmain in your system.Ifthe samepathogen were to enter your body again,your immune system wouldalmost certainly destroy it before youbecame ill.This resistance to a sicknessImmunity takes two forms:passiveand active.When babies are first born,they have only the immune defensesansferred to them by their mothers.They have not had the chance to developantibodies oftheir own.This type ofimmunity is called passive immunity.tibodies are not produced by the per-sonÕs own body but given to the bodyfrom another source.Babies develop their own antibodies after ou have active immunity whenever your body makes its own anti-bodies.Your body will again fight against any specific pathogen youhave developed antibodies against.For example,it is most unlikely that you will get chicken pox twice.Check Your ReadingWhat is the difference between active and passive immunity?Most diseases can be prevented or treated.Given enough time,your immune system will fight offmost diseases.some infections can cause significant and lasting damagebefore they are defeated by the bodyÕs defenses.Other infections are sostrong that the immune system cannot successfully fight them.Medicaladvances in the prevention and treatment ofdiseases have reduced theisks ofmany serious illnesses.nother way to develop an immunity is to receive a Vaccinesntain small amounts ofweakened or dead pathogens that stimulatean immune response.Your B cells are called into action to create anti-bodies as ifyou were fighting the real illness.The pathogens are usuallyeakened or dead so that you will not get sick,yet they still enableour body to develop an active immunity. vaccine. immunity. COMPARE