Chapter 15 Microbiology Innate Immunity

Complement proteins

an important part of the second line of defense

Other First Line Defenses:

anitmicrobial peptides are found in mucous membranes and in neutrophils. These peptides act against a variety of potential pathogens, being triggered by sugar and protein molecules on the external surfaces of microbes. -some antimicrobial peptides act only against Gram-postive bacteria or Gram-negative bacteria, other act against both and still others act agaist protozoa, enveloped viruses or fungi -some punch holes in the cytoplasmic membranes of the pathogens and others interrupt internal signaling or enzymatic action. Some anitmicrobial peptides are cheotactic facters that recruit leukocytes to the site, while other assmeble to form fibers and microscopic nets that ensnare invading bacteria

2. NOD proteins

- NOD proteins are another set of receptors for microbial molecules such as PAMPs but NOD proteins are located inside a cell rather than as part of a cells cytoplasmic membrane. -Scientist have studied NOD proteins that bind to components of Gram-negative bacterias cell walls and RNA of viruses, such as those that cause AID, hepatitis C and mononucleosis. -NOD proteins trigger inflammation, apoptosis and other innate immune response against bacterial pathogens -Mutations in NOD genes are assoicated with several inflammatory bowel diseases, including Crohns disease.

Complement system: -activated in three ways: 1. In the classical pathway, antibodies active complement 2. In the alternative pathway, pathogens or pathogenic products (such as bacterial endotoxins and glycoproteins) activate complement 3. In the lectin pathway, microbial polysaccharides bind to activating molecules -complement proteins react with one another in an amplifying sequence of chemical reactions in which the product of each reactions becomes an enzyme that catalyzes the next reaction many times over, such reactions are called cascades b/c they progress in away that can be likened to a rock avalanche in which one rock dislodges several rock. The products of each step in the complement cascade initiate other reactions often with wide-ranging effects in the body

- a set of serum proteins designated numerically according to the order of their discovery -these proteins initially act as opsonins and chemotacti factors and indirectly trigger inflammation and fever. The end result of full complement activation is lysis of foreign cells -

how is it that phagocytes destroy invading pathogens and leave the bodys own healthy cells unharmed?

- some phagocytes have cytoplasmic membrane receptors for various microbial surface components lacking on the bodys cells such as cell wall components or flagellar proteins -Opsonins such as complement and antibody provide a signal to the phagocyte

what is included in the third line of defense? (adaptive immunity)

-B-cells (lymphocytes) (respond against unique species and strains of pathogens and alter the bodys defenses such that they act more effectivley upon subsequent infection with the same specific strain) -T-cells

Phagosome Maturation and Microbial Killing

-a serious of membranous organelles within the phagocyte fuse with newly formed phagosomes to form digestive vesicles -one organelle, the lysosome, adds digestive chemicals to the maturing phagsome, which is now called a phagolysosome -phagolysosome contain antimicrobial substance, such as highly reactive, toxic forms of oxygen, in an environment with a pH of about 5.5 due to the active pumping of H+ from the cytosol. -These factors, along with 30 or so different enzymes such as lipases, proteases, nucleases and a variety of others, destroy the engulfed microbes -most pathogens are dead within 30 mintues. Though some bacteria contain virulence factors (such as waxy cell walls) that resist a lysosomes action. In the end, a phagolysosome is known as a residual body

Ingestion

-after phagocytes adhere to pathogens, they extend pseudopods to surrond the microbe. The encompassed microbe is internalized as the pseudopods fuse to form a food vessicle called a phagosome

Lysozyme

-an enzyme that destroys the cells walls of bacteria by cleaving the bonds b/w the sugar and subunits of the walls. -bacteria without cell walls are more susceptible to osmotic shock and digestion by other enzymes within pahgocytes

Defense Components of Blood: 1. Plasma: -mostly water containing electrolytes (ions), dissolved gases, nutrients and most relevant to the bodys defenses--a variety of proteins -some plasma proteins are involved in inflammation and in blood clotting, a defense mechanism that reduces both blood loss and the risk of infection. -when clotting factors have been removed from the plasma, as when blood clots, the remianng liquid is called serum -Humans require iron for metabolism: it is a component of cytochromes of electron transport chains, fuctions as an enzyme cofactor and is an essential part of hemoglobin-- the ozygen carrying protein of erthrocytes -Iron is relaitvley insoluble in humans and it is transported in plasma to cells by transport protein called transferrin. -Excess iron is stored in the liver bound to another protein called ferritin.

-blood is a complex liquid tissue composed of cells and portions of cells within a fluid called plasma. -some bacteria such as staphylococus aureus respond to a shortage of iron by secreting their own iron-binding proteins called siderophores -because siderophores have a greater affinity for iron that does transferrin, bacteria that produce siderophores can in effect steal iron from the body. In response, the body produces lactoferrin, which retakes the iron from the bacteria by its even greater affinity. -thus the body and the pathogens engage in a kind of chemical tug of war for the posssesion of iron. -some pathogens bypass this contest altogether, for examples, S. aureus and related pathogens can secrete the protein hemolysin, which punches holes in the cytoplasmic membranes of red blood cells, releasing hemoglobin. -other bacterial proteins then bind hemoglobin to the bacterial membrane and strip it of its iron. -Neisseria meningitidis, a pathogen that causes often fatal meningitits, produces receptors for transferrin and plucks iron from the bloodstreams as it flows by

Defensive Blood Cells: Leukocytes: -Leukocytes, the formed elements that are directly involved in defending the body against invaders, are commonly called white blood cells beause they form a whitish layer when the components of blood are separated within a test tube -the proportions of leukocytes, as determined in a differential white blood cell count, can serve as a sign of disease -an increase in the percentage of eosinophils can indicate allergies or infection with parasitic worms -bacterial diseases typically result in an increase in the number of leukocytes and increase in the percentage of neutrophils, whereas viral infections are associated with an increase in the relative number of lymphocytes

-cells and cell fragments suspended in the plasma are called formed elements -in a process called hematopoiesis, blood stem cells located principally in the bone marrow within the hollow cavities of he large bones produced three types of formed elements: -platelets -erythrocytes -leukocytes 1. Erythrocytes: the most of the formed elements, carry oxygen and CO2 in the blood 2. Platelets: which are pieces of large cells called megakaryocytes that have split into small portions of cytoplasm surronded by cytoplasmic membranes, are involved i blood clotting

Elimination

-digestion is not always complete and phagocytes eliminate remnants of microorganisms via exocytosis, a process that is essentially the reverse of ingestion. -Some microbial components are specially processed and remain attached to the cytoplasmic membrane of some phagocytes, particularly dendritic cells.

The Classical Pathway -complement got its name from events in the originally discovered "classical" pathway. -In this pathway the various proteins act to "complement"or act in conjunction with, the action of antibodies. -Complement enzymes in early events cleave other complement molecules to form fragments, which are designated with lowercase leters -Most fragments have specific and important roles in achieving the functions of the complement system. Some combine to form new enzymes ; some act to increase vascular permeabllity , which increases diapedesis; others enhance inflammation; and still others are involved as chemotactic factors, attracting phagocytes, or in opsonization -one end product of a full cascade is a membrane attack comples (MAC), which forms a circular hole in a pathogens membrane. The production of numerous MACs leads to lysis in a wide variety of bacterial and eukaryotic pathogens. -Gram-negative bacteria, such as the bacterium causing gonorrhea, are particularly sensitive to the prodcution of MACs via the complement cascade becasue their outer membranes are exposed and susceptible. -Gram-postive bacterium, which has a thick layer of peptidoglycan overlying its cytoplasmic membrane, is typically resistant to the MAC-induced lytic properties of complement, though it is susceptible to the other effect of the complement cascade

-fragment C4b also acts an opsonin. -Fragments C3a and C5a function as chemotactic factors, attracting phagocytes to the site of infection. -C4a are also inflammatory agents that trigger increased vascular permeability and dilation.

The role of Mucous Memmbranes in Innate Immunity (second part of the first line of defense): -cover all body cavities that are open to the outside environement.

-mucous membranes line the lumens of the respiratory, urinary, digestive and reproductive tracts. -mucous membranes act nonspecifically to limit infectons both physically and chemically. -mucous membranes are moist and have two distinct layers: the epithelium, in which cells form a covering that is superficial (closet to the surface, in this case the lumen) and a deeper connective tissue layer that provides mechanical and nutritive support forthe epithelium. -Epithelial cells of mucous membranes are packed closely togthter, like those of the epidermis but they form only a thin layer. In some mucous membranes, the epithelium is only a single cell thick. Unlike surfae epidermal cells, surface cells of mucous membranes are alive and play roles in the diffusion of nutrients and oxygen (in the digestive, respiratory, and female reproductive systems) and in the elimination of wastes (in the urinary, respiratory, and female reproductive) -the thin epithelium on the surface of a mucous membrane provides a less efficeint barrier to the entrance of pathogens than the multiple layers of dead cells found at the skins surface -respiratory and reproductive systems are common portals of entry for pathogens. Nevertheless the epithelial cells of mucous membranes are tightly packed to prevent the entry of many pathogens and the cells are conitnually shed and then replaced by stem cells which are generative cells capable of dividng to form daughter cells of various types. -one effect of mucousal shedding is that it carries attaached microorganisms away -dendritic cells reside below the mucus epithelium to phagocytize invaders. These cells are also able to extend pseudopods b/w epithelial cells to "sample" the contents of the lumen, helping to prepare adaptive immune responses against particular pathogens that might breach the mucosal barrier. the epithelia of some mucuous embranes have still other mean of removing pathogens, in the mucous membrane of the trachea, for example, the stem cells produce both goblet cells, whic secrete an extremely sticky mucus that traps bacteria and other pathogens and ciliated columnar cells, whose cilia propel the mucus and its trapped particles and pathogens up from the lungs. The effect of the action of the cilia is often lkened to that of an esclator. - Mucus carried into the throat is coughed up and either swallowed or expelled -mucus membranes produce chemicals that defend against pathogens. Nasal mucus contains lysozyme, which chemically destroys bacterial cell walls. Mucus also cotians antimicrboial peptides

Killing by Neutrophils

-neutrophils do not always devour pathogens; they can destroy nearby microbial cells without phagocytosis. -Enzymes in a neutrophils cytoplasmic membrane add electrons to oxygen, creating highly reactive superoxide radical O2- and hydrogen peroxide (H2O2) -another enzyme converts these into hypochlorite, the active antimcrobial ingredients in household bleach. These chemicals can kill nearby invaders. Another enzyme in the membrane makes nitric oxide, which is a powerful inducer of inflammation -neutrophils disable microorganism in their vicinity. They generate webs of extracellular fibers nicknamed NET's for neutrophil extracellular traps. -neutrophils synthesize NETs via a unique form of a cellular suicide invovling the disintergration of their nuclei. -As the nuclear envelope breaks down, DNA and histones are released into the cytosol and the mixing of nuclear components with cytoplasmic granule membranes and proteins forms NET fibers -Reactive oxygen species--superoxide and peroxide-- then kill the neutrophil. -The NETs are released from the dying cells as its cytoplasmic membrane reuptures -NETs trap both Gram-positive and Gram-negative bacteria, immobilizing them and sequestering them along with antimicrobial peptides, which kill the bacteria.

Dilation and Increased Permeability of Blood Vessels -Bradykinin and Histamine causes vasodilation of the bodys smallest arteries (arterioles) -Vasodilation results in delivery of more blood to the site of infection, which in turn delivers more phagocytes, oxygen, and nutrients to the site. -Inflammatory mediators cause cells that line blood vessels to make adhesion molecules, which are receptors for leukocytes. -Bradykinin, prostaglandins, leukotrienes, and histamine also make small veins more permealbe that is they cause cells lining the vessels to contract and pull apart, leaving gaps in the walls through which phagocytes can move into the damaged walls through which phagocytes can move into the damaged tissue and fight invadesrs. Increase permeabilty also allows delivey of more bloodborne antimicorbial chemicals to the site -dilation of blood vessels in response to inflammaory mediators results in the redness and localized heat associated with inflammation. -prostaglandins and leukotrienes cause fluid to leak from the more permealbe blood vessels and acccumulate in the surronding tissues, resulting in edema, which is reponsible for much of the pain of inflmamation as pressure is exerted on nerve endings -vasodilation and increased permeability also deliver fibrinogen, the bloods clotting protein. Clots forming at the site of injury or infection wall off the area and help prevent pathogens and their toxins from spreading. one result is the formation of pus, a fluid containing dead tissues cells, leukocytes and pathogens in the walled off area. -Pus may push up toward the surface and erupt or it may remain isolated in teh body where it is slowly absorbed over a period of days called abscess. Pimples, boils and pustules are examples of abscesses -The signs and symptoms of inflammation can be treaed with antihistamines, which block histamine receptors on blood vessels walls, or with antiprostaglandins. One of the ways aspirin and ibuprofen reduce pain is by acting as antiprostaglandins.

-part of the bodys initial response to an injury or innvasion of pathogens is lo, calized dilation (increase in diamter ) of blood vessels in the affected region. - the process of blood clotting triggers the conversion of a soluble plasma protein into a nine- amino acid peptide chain called bradykinin, which is a potent meidator of inflammation. -patrolling macrophages, using Toll-like receptors and NOD protein to identify invaders, release other inflammatory chemicals, including prostaglandins and leukotrienes. -Basophils, platelets and specialized cells located in connective tissue--called mast cells--also release inflammatory mediators such as histamine, when they are exposed to complement fragments C3a or C5a

Anitmicrobial peptides (defensins)

-postively charge chains of 20 to 50 amino acids that act against microorganism. -Sweat glands secrete a class of antimicrobials called dermcidins. -dermicidins are broad-spectrum antimicrobials that are active against many gram-negative and gram-positive bacteria and fungi. -peptide active on the surface of the skin , dermicidins are insensitve to low ph and salt

the second line of defense is composed of?

-protective cells, bloodborne chemicals, and process that inactivate or kill invaders

what is the first line defense composed of?

-skin and mucus mebranes of the: -respiratory -digestive -urinary -reproductive system

Agranulocytes: -appears uniform when viewed via light microscopy, though granules do become visible with an electron microscope.

-smallest leukocytes and have nuclei that nearly fill the cells and monocytes, which are large agranulocytes with slightly lobed nuclei -Monooctyes leave he blood and mature into macrophages, which are phagocytic cells of the second line of defense. Their initial function is to devour foreign objects, including bacteria, fungi, spores and dust as well as dead body cells -Macrophages are named for their location in the body. -Wandering macrophages leave the blood via diapedesis and perform their scavenger function while traveling throughout the body, including extracelular spaces. -Fixed Macrophages generally phagocytize within specific organs, such as the heart chambers, blood vessels and lymphatic vessels. -a special group of phagocytes are not WBC'sbut are dendritic cells, multibranched cells plentiful throughout the body, particularly in the skin and mucous membranes. Dendritic cells await microbial invaders, phagocytize them, and inform cells of adaptive immunity that there is a microbial invasion.

The role of the Lacrimal Apparatus in Innate Immunity:

-the lacrimal apparatus is a group of structures that produce and rain away tears -Lacrimal glands, located above and the sides of the eyes, secrete tears into lacrimal gland ducts and onto the surface of the eyes. -The tears either evaporate or drain into small lacrimal canals, which carry them into nasolacrimal ducts that empty into the nose. There, the tears join the nasal mucus and flow into the pharynx, where they are swallowed. The blinking action of eyelids spread the tears and washes the surfaces of the eyes. If the eyes are irratiated, increased tear production floods the eyes, carrying the irritant away. In addition to their washing action, tears contain lysosyme, which destroys bacteria.

Roles of Skin in Innate Immunity: 1. epidermis: composed of multiple layers of tightly packed cells. -constitutes a physical barrier to most bacteria, fungi, and viruses -very few pathogens can penetrate the layers of epidermal cells unless the skin has been burned, broken or cut -the deepest cells of the epidermis continually divide, pushing their daughter cells toward the surface. As the daughter cells are pushed toward the surface they flatten and die and are eventually shed in flakes. -Mircoorganisms that attach to the skins surface are sloughed off with flakes of dead cells. -contains phagocytic cells calle dendritic cells. The slender, fingerlike process of dendritic cells extend among the surronding cells, forming an almost continuous network to intercept invaders -dendritic cells both phagocytize pathogens nonospecifically and play a role in adapative immunity 2. Dermis defends nonspecifically -contains tough fibers of a protein called collagen. These give the skin strength and pliability to prevent jabs and scrapes form penetrating the dermis and introducing mircrogoranisms. -blood vessels in the dermis deliever defenseive cells and chemicals. -dermal cells secrete antimicrobial peptides and sweat glands secrete perspiration, which contains sat, antimcrobial peptides and lysozyme. -salt draw water osmotically from invading cells, inhibiting their growth and killing them.

-the organ of the body with the greatest surface area -outer layer epidermis and deeper dermis contains hair follicles, glands and nerve ending

The role of Normal Microbiota in Innate Immunity:

-the skin and mucous membranes of the body are normally home to a variety of protozoa, fungi, bacteria, and viruses -these normal microbiota play a role in protecting the body by competing with potential pathogens in a variety of ways, a situation called microbial anatagonism -a variety of activities of the normal microbiota make it less likely that a pathogen can compete with them and produce disease. Microbiota consume nutrients, making them unavailiable to pathogens. Normal micobiota can change the pH, creating an environment that is favorable for themselve but unfavoralbe to other microorganisms. -the presence of microbiota stimulates the bodys second line of defense -animals raised in an axenic3 that is one free of all other organisms o and pyr virues, are slower to defend themselves when exposed to pathogen. -members of the normal microbiota in the intesines boost the bodys production of anitmicorbial substances -resident microbiota of the intestines improve overall, health by providing serveral vitamins, including biotin and pantothenic acid, (Vitamin B5), which are important in glucose metabolism; folic acid, which is essential for the production of the purine and pyrimidine bases of nucleic acids and the precursor of vitamin K, which has an important role in blood clotting.

3. Interferons: proteins molecules released by host cells to nonspecifically inhibit the spread of viral infections. -their lack of specficity means that interferons produced against one viral invader protect somewhat against infection by other types of viruses -interferons produced against one viral invader protect somewhat against infection by other types of viruses -cause malaise, muscle aches, chills, headache, and fever which are typically associated with viral infections.

-viruses uses a hosts metabolic machinery to produce new viruses -different cell types produce one of two basic types of interferon when stimulated by viral nucelic acid binding to certain Toll-like receptors (TLR3, TLR7, or TLR8). Interferons within any given type share certain physcial and chemical features, though they are specfic to the species that produces them. -type I interferons--also known as alpha and beta interferons--are present early in viral infections, whereas type II (gamma) interferon appears somewhat later in the course of infection

The bodys Second Line of Defense -includes: *phagocytes, *antimicobial chemicals such as complement and interferons *inflammation *fever *natural killers

-when the pathogens succeed in penetrating the skin or mucous membranes, the bodys second line of innate defense comes into play

4. Type I (Alpha and Beta) Interferons

-within hours after infection, virally infected monocytes, macrophages, and some lyphocytes secrete small amounts of alpha interferon (IFN-alpha) -fibroblasts, which are undifferentiated cells in such connective tissues as cartilage, tendon and bone, secrete small amounts of beta interferon (IFN-beta) when infected by viruses. The structures of alpha and beta interferons are similar and their action are identical -Interferons do not protect the cells that secrete them---these cells are already infected with viruses. -interferons activate natural killer lymphocytes and trigger proctective steps in neighboring uninfected cells. -Alpha and beta interferons bind to interferon receptors on the cytoplasmic membranes of neigboring cells. Such biding production of antiviral proteins (AVPs), which remain inactive within these cells until AVPs bind to viral nucleic acids, particulary double-stranded RNA, a molecule that is common among viruses but generally abesent in eukaryotic cells -at least two types of antiviral proteins are produced: oligoadenylate snythetase, the action of which results in the destruction of mRNA and protein kinase, which inhibits protein synthesis by ribosomes -AVP enzymes essentially destroy the protein production system of the cell, preventing viruses from being replicated. Cellular metabolism is also affected negatively. The antiviral state last three to four days, which may be long enough for a cell to rid itself of viruses but still a short enough period for the cell to survive without protein produciton

Killing by Natural Killer Lymphocytes

-works by secreting toxins onto the surfaces of virally infected cells and neoplasms (tumors). -NK cells indentify and spare normal body cells because the latter express membrane proteins similar to those on the NK cells

Inflammation -nonspecific response to tissue damage resulting from a variety of causes, including heat, chemicals, UV light (sunburn), abrasions, cuts and pathogens

1. Acute inflammation: develops quickly , is short lived, is pically beneficail and results in the elimination or resolution of whatever conditon precipitated it -results in dilation and increased permeability of blood vessels, migration of phagocytes and tissues repairs. 2. long lasting chronic inflammation causes damge (even death) to tissues resulting in disease. Both acute and chronic inflammation exhibit similar signs and symptoms, including redness in light-colored skin (rubor) , localized heat (calor), edema (swelling) and pain (dolor)

Granulocytes (WBC) : have large granules in their cytoplasm that stain different colors depending on the type of granulocytes and dyes used

1. Basophils : stain blue with the basic dye methylene blue 2. Eosinophils: stain red to orange with the acidic dye eosin 3. Neutrophils: also known as polymorphonuclear leukocytes (PMN's), stain lilac with a mixture of acidic and basic dyes -both neutrophils and eosinophils phagocytize pathogens and both can exit the blood to attack invading microbes in the tissues by squeezing between the cells lining capillaries in a process called diapedesis -Eosinophils are involved in defending the body against parasitic worms and are present in large number during many allegeric rxns -basophils can also leave the blood, though they are not phagocytic, instead they release inflammatory chemicals.

Phagocytosis: "eating by cells" -phagocytic defense cells of the body--uses phagocytosis to rid the body of pathogens that have evaded the bodys first line of defense.

1. Chemotaxis: movement of a cell either toward a chemical stimulus (positive cehmotaxis) or away from a chemical stimulus (negative chemotaxis). - In the case of phagocytes, postive chemotaxis involves the use of pseudopods to crawl toward microorganisms at the site of an infection -Chemicals that attract phagocytic leukocytes include microbial components and secretions, components of damaged tissues and white blood cells and chemotactic factors. -chemotactic factors include defensinns, peptides derived from complement and chemicalls called chemokines, which are released by leukocytes already at the site of infections 2. Adherence: after arrriving at the site of an infecton, phgocytes attach to microorganisms through the binding of complementary chemicals such as glycoproteins found on the membranes of cells. -some bacteria have virulence factors, such as slippery capsules that hinder adherence of phagocytes. -Such bacteria are more readily phagocytized if they are pushed up against a surface, such as connective tissues, the wall of blood vessles or a blood clot -all pathogens are more reaidly phagocytized if they are first covered with anitmicrobial proteins such as complement proteins or the specific antimicrobial proteins called antibodies. This coating process is called opsonization and the proteins are called opsonins -opsonins increase the number and kinds of binding sites on a microbes surface

Nonphagocytic Killing: -eosinphils, natural killer cells, and neutrophils can accomplish killing w/o phagocytosis

1. Killing by Eosinophils: -eosinophils can phagocytize and secrete antimicrobial chemicals. -They attack parasitic helminths (worms) by attaching to the worms surface, where they secrete extracellular protein toxins onto the surface of the parasite. These weaken the helminth and may even kill it. -Eosinophilia, an abnormally high number of eosinophils in the blood, is often indicative of helminth infestation of eosinophils in the blood, is often indicative of helminth infestation or allergies. -uses lipopolysaccharide from Gram-negative bacterial cell walls triggers eosinophils to rapidly eject mitochondrial DNA, which combines with previously extruded eosinophil proteins to form a physical barrier.

Nonspecific Chemical Defenses Against Pathogens: -defensive chemicals include lysoszyme and defensins as well as Toll-like receptors, NOD proteins, interferons and complement

1. Toll-like Receptors (TLRs): -TLRs are intergral proteins of the cytoplasmic membranes of phagocytic cells. -TLRs act as an early warning system, triggering your bodys responses to a number of molecules that are shared by various bacterial or viral pathogens and are absent in humans -These microbial molecules include peptidoglycan, lipopolysaccharide, flagellin, unmethylated pairs of cytosine and guanine nucleotides from bacteria and viruses, double-stranded RNA, and single-stranded viral RNA, referred to as pathogen-associated molecular patterns (PAMPs). -Ten TLRs are known for humans. TLRs 1,2,4,5 and 6 are found spanning cytoplasmic membranes, while TLRs 3, 7, 8 and 9 span phagosome membranes. -Some TLRs act alone; others act in pairs to recognize a particular PAMP -binding of a PAMP to a Toll-like receptor initiates a number of defensive responses, including apoptosis (cell suicide) of an infected cell, secretion of inflammatary mediators or interferons, or production of chemical stimulants of adaptive immune response collapse, leaving the body open to attack by myraid pathogens

what are the characteristics of Innate defense?

1. born with it 2. rapid and works against a wide variety of pathogens including parastic worms, protozoa, fungi, bacteria and virus

how does a pathogen cause disease?

1. gain access, either by penetrating the surface of the skin or entering through some other portal of entry 2. attach itself to host cells 3. evade the body defense mechanism long enough to produce harmful changes.

Migration of Phagocytes Margination: they squeeze b/w the cells of the vessels wall (diapedesis) and eneter the site of infection, usually within an hour of tissue damage. The phagocytes then destroy pathogens via phagoctyosis -once monocytes leave the blood, they change and become wandering macropahges, whic are component of pus

first phagocytes to arrive are often neutrophils, which are then followed by monocytes are attracted to the site of infection first.

the first & second line of defense are called?

innate

Inactivation of Complement

membrane-bound proteins on the bodys cells bind with and break down activated complement proteins, therby interrupting the complement cascade before damage can occur