front 1 Innate Defense System (nonspecific) | back 1 Innate Defense System (nonspecific)
is always prepared, responding within minutes to protect the body from all foreign substances. This system has two “barricades.” The first line of defense is the external body membranes—intact skin and mucosae. The second line of defense, called into action whenever the first line has been penetrated, uses antimicrobial proteins, phagocytes, and other cells to inhibit the invaders’ spread throughout the body. The hallmark of the second line of defense is inflammation. |
front 2 Adaptive Defense System (specific) | back 2 Adaptive Defense System (specific)
is more like an elite fighting force equipped with high-tech weapons that attacks particular foreign substances and provides the body’s third line of defense. This defensive response takes considerably more time to mount than the innate response. Although we consider them separately, the adaptive and innate systems always work hand in hand. |
| back 3 Immune System
is a functional system rather than an organ system in an anatomical sense. Its “structures” are a diverse array of molecules plus trillions of immune cells (especially lymphocytes) that inhabit lymphoid tissues and circulate in body fluids. |
| back 4 Phagocytes
(phago = eat) Engulf and destroy pathogens that breach surface membrane barriers; macrophages also contribute to adaptive immune responses |
| back 5 Pathogen
A bacterium, virus, or other microorganism that can cause disease. |
| back 6 Macrophages
(“big eaters”) The chief phagocytes which derive from white blood cells called monocytes that leave the bloodstream enter the tissues. |
| back 7 Neutrophils
the most abundant type of white blood cell, become phagocytic on encountering infectious material in the tissues. |
| back 8 Phagocytosis
The ingestion of bacteria or other material by phagocytes and ameboid protozoans. |
| back 9 Phagosome
A vacuole in the cytoplasm of a cell, containing a phagocytosed particle enclosed within a part of the cell membrane. |
| back 10 Phagolysosome
A cellular body that is formed by the union of a phagosome or ingested particle with a lysosome that contains hydrolytic enzymes |
| back 11 Adherence
phagocyte must adhere or cling to the pathogen |
| back 12 Opsonization
complement proteins or antibodies coat foreign particles |
front 13 Natural killer (NK) cells | back 13 Natural killer (NK) cells
“police” the body in blood and lymph, are a unique group of defensive cells that can lyse and kill cancer cells and virus-infected body cells before the adaptive immune system is activated. Non-specific - they can eliminate a variety of infected or cancerous cells by detecting the lack of “self” cell-surface receptors and by recognizing certain surface sugars on the target cell. |
| back 14 Inflammatory Response
triggered whenever body tissues are injured by physical trauma (a blow), intense heat, irritating chemicals, or infection by viruses, fungi, or bacteria.
The inflammatory response has several beneficial effects:
1. Prevents the spread of damaging agents to nearby tissues
2. Disposes of cell debris and pathogens
3. Sets the stage for repair |
front 15 Toll-Like Receptors (TLRs) | back 15 Toll-Like Receptors (TLRs)
surface membrane receptors that play a central role in triggering immune responses. |
| back 16 Mast cells
a key component of the inflammatory response, release the potent inflammatory chemical histamine |
| back 17 Histamine
Granules of mast cells and basophils. Released in response to mechanical injury, presence of certain microorganisms, and chemicals released by neutrophils. Promotes vasodilation of local arterioles. Increases permeability of local capillaries, promoting exudate formation. |
| back 18 Kinins
A plasma protein, kininogen, is cleaved by the enzyme kallikrein found in plasma, urine, saliva, and in lysosomes of neutrophils and other types of cells. Cleavage releases active kinin peptides. Promotes vasodilation of local arterioles. Increases permeability of local capillaries, promoting exudate formation. Also induce chemotaxis of leukocytes and prompt neutrophils to release lysosomal enzymes, thereby enhancing generation of more kinins. Induce pain. |
| back 19 Prostaglandins
Fatty acid molecules produced from arachidonic acid found in all cell membranes; generated by enzymes of neutrophils, basophils, mast cells, and others. Promotes vasodilation of local arterioles. Increases permeability of local capillaries, promoting exudate formation. Also induce neutrophil chemotaxis. Induce pain. |
| back 20 Platelet
derived growth factor (PDGF) - Secreted by platelets and endothelial cells. Stimulates fibroblast activity and repair of damaged tissues. |
| back 21 hyperemia
congestion with blood, accounting for the redness and heat of an inflamed region. |
| back 22 Intact skin epidermis
Forms mechanical barrier that prevents entry of pathogens and other harmful substances into body |
front 23 Acid mantle Skin secretions | back 23 Acid mantle Skin secretions
(sweat and sebum) make epidermal surface acidic, which inhibits bacterial growth; also contain various bactericidal chemicals |
| back 24 Keratin
Provides resistance against acids, alkalis, and bacterial enzymes |
| back 25 Intact Mucous Membranes
Form mechanical barrier that prevents entry of pathogens |
| back 26 Mucus Traps
microorganisms in respiratory and digestive tracts |
| back 27 Nasal Hairs
Filter and trap microorganisms in nasal passages |
| back 28 Cilia
Propel debris-laden mucus away from nasal cavity and lower respiratory passages |
| back 29 Gastric Juice
Contains concentrated hydrochloric acid and protein-digesting enzymes that destroy pathogens in stomach |
| back 30 Acid Mantle of Vagina
Inhibits growth of most bacteria and fungi in female reproductive tract |
front 31 Lacrimal Secretion (tears), saliva | back 31 Lacrimal Secretion (tears), saliva
Continuously lubricate and cleanse eyes (tears) and oral cavity (saliva); contain lysozyme, an enzyme that destroys microorganisms |
| back 32 Urine
Normally acid pH inhibits bacterial growth; cleanses the lower urinary tract as it flushes from the body |
| back 33 Interferons
Proteins released by virus-infected cells and certain lymphocytes that protect uninfected tissue cells from viral takeover; mobilize immune system |
| back 34 Complement
complement system, or simply complement, refers to a group of at least 20 plasma proteins that normally circulate in the blood in an inactive state. Lyses microorganisms, enhances phagocytosis by opsonization, and intensifies inflammatory and immune responses |
| back 35 Leukocytosis
an increase in WBCs that is a characteristic of inflammation. |
| back 36 Margination
Systemic response initiated by pyrogens; high body temperature inhibits microbial multiplication and enhances body repair processes |
| back 37 clinging of phagocytes to the inner walls of the capillaries and postcapillary venules |
| back 38 Diapedesis
the outward passage of blood cells through intact vessel walls |
| back 39 Chemotaxis
The characteristic movement or orientation of an organism or cell along a chemical concentration gradient either toward or away from the chemical stimulus |
| back 40 Antimicrobial Proteins
enhance the innate defenses by attacking microorganisms directly or by hindering their ability to reproduce. |
| back 41 Viruses
essentially nucleic acids surrounded by a protein coat—lack the cellular machinery to generate ATP or synthesize proteins. They do their “dirty work,” or damage, in the body by invading tissue cells and taking over the cellular metabolic machinery needed to reproduce themselves. |
| back 42 Interferons (IFNs)
help protect cells that have not yet been infected. The IFNs diffuse to nearby cells, where they stimulate synthesis of proteins which then “interfere” with viral replication in the still-healthy cells by blocking protein synthesis and degrading viral RNA |
front 43 Complement Classical Pathway | back 43 Complement Classical Pathway
involves antibodies, watersoluble protein molecules that the adaptive immune system produces to fight off foreign invaders. |
front 44 Complement Alternative Pathway | back 44 Complement Alternative Pathway
is triggered when spontaneously activated C3 and factors B, D, and P interact on the surface of certain microorganisms. |
front 45 MAC (membrane attack complex) | back 45 MAC (membrane attack complex)
forms and stabilizes a hole in the membrane that ensures lysis of the target cell by inducing a massive influx of water. |
| back 46 Pyrogen
a fever-producing chemical |
| back 47 Antigens
substances that can mobilize the adaptive defenses and provoke an immune response. They are the ultimate targets of all adaptive immune responses. |
| back 48 Humoral immunity
also called antibodymediated immunity, is provided by antibodies present in the body’s “humors,” or fluids. Though they are produced by lymphocytes (or their offspring), antibodies circulate freely in the blood and lymph, where they bind primarily to bacteria, to bacterial toxins, and to free viruses, inactivating them temporarily and marking them for destruction by phagocytes or complement. |
| back 49 Cellular Immunity
cell-mediated immunity. When lymphocytes themselves rather than antibodies defend the body. The protective factor is living cells. Cellular immunity also has cellular targets—virus-infected or parasiteinfected tissue cells, cancer cells, and cells of foreign grafts. The lymphocytes act against such targets either directly, by killing the foreign cells, or indirectly, by releasing chemical mediators that enhance the inflammatory response or activate other lymphocytes or macrophages. |
| back 50 Hapten
incomplete antigen; a specific nonprotein substance which does not itself elicit antibody formation but does elicit the immune response when coupled with a carrier protein |
| back 51 Immunogenicity
the property enabling a substance to provoke an immune response, or the degree to which a substance possesses this property |
| back 52 Self-Antigens
are not foreign or antigenic to you, but they are strongly antigenic to other individuals. |
| back 53 MHC proteins
proteins that mark a cell as self is a group of glycoproteins |
front 54 Major Histocompatibility Complex (MHC) | back 54 Major Histocompatibility Complex (MHC)
genes that code for MHC proteins |
| back 55 B lymphocytes
B cells oversee humoral immunity. |
| back 56 T lymphocytes
T cells are non-antibody-producing lymphocytes that constitute the cell-mediated arm of adaptive immunity. |
| back 57 Immunocompetence
The ability of a lymphocyte to recognize its one specific antigen by binding to it. |
| back 58 Self-tolerance
lymphocyte is relatively unresponsive to self-antigens so that it does not attack the body’s own cells. |
| back 59 Primary Lymphoid Organs
The lymphoid organs where the lymphocytes become immunocompetent—thymus and bone marrow |
| back 60 Naïve
Immunocompetent B and T cells that have not yet been exposed to antigens |
| back 61 Positive Selection
identifies T cells whose receptors are capable of recognizing (binding) self-MHC molecules |
| back 62 Negative Selection
T cells that make it through positive selection are then tested to make sure that they do not recognize (bind tightly) self-antigens displayed on self-MHC. If they do, they are eliminated by apoptosis |
| back 63 Somatic Recombination
gene segments are shuffled and combined in different ways to produce functional antibody genes |
| back 64 Antigen
Presenting Cells (APCs) - major role in immunity is to engulf antigens and then present fragments of them, like signal flags, on their own surfaces where they can be recognized by T cells. |
| back 65 Antigen Challenge
the first encounter between an immunocompetent but naive lymphocyte and an invading antigen |
| back 66 Clonal Selection
B cell grow and then multiply rapidly to form an army of cells all exactly like itself and bearing the same antigen-specific receptors |
| back 67 Hormonal Immunity
The component of the immune system involving antibodies that are secreted by B cells and circulate as soluble proteins in blood plasma and lymph. |
| back 68 Plasma Cells
the antibody-secreting effector cells of the humoral response. |
| back 69 Memory Cells
Clone cells that do not become plasma cells They are longlived and can mount an almost immediate humoral response if they encounter the same antigen again at some future time |
| back 70 Primary Immune Response
occurs on first exposure to a particular antigen, has a lag period of 3 to 6 days after the antigen challenge. |
front 71 Secondary Immune Response | back 71 Secondary Immune Response
If (and when) someone is reexposed to the same antigen, whether it’s the second or the twenty-second time. These responses are faster, more prolonged, and more effective, because the immune system has already been primed to the antigen, and sensitized memory cells are already in place “on alert.” |
| back 72 Immunological Memory
Memory cells that have been primed to the antigen, and cells are already in place “on alert. |
| back 73 Active Humoral Immunity
When your B cells encounter antigens and produce antibodies against them |
front 74 Active Humoral Immunity Naturally Acquired | back 74 Active Humoral Immunity Naturally Acquired
when you get a bacterial or viral infection, during which time you may develop symptoms of the disease and suffer a little (or a lot). |
front 75 Active Humoral Immunity Artificially Acquired | back 75 Active Humoral Immunity Artificially Acquired
when you receive vaccines. |
| back 76 Passive humoral immunity
The antibodies are harvested from the serum of an immune human or animal donor. As a result, your B cells are not challenged by antigens, immunological memory does not occur, and the protection provided by the “borrowed” antibodies ends when they naturally degrade in the body. Differs from active immunity, both in the antibody source and in the degree of protection it provides. Instead of being made by your plasma cells |
| back 77 Antibodies
also called immunoglobulins constitute the gamma globulin part of blood proteins. antibodies are proteins secreted in response to an antigen by effector B cells called plasma cells, and they are capable of binding specifically with that antigen |
| back 78 Antibody Monomer
four looping polypeptide chains linked together by disulfide (sulfur-to-sulfur) bonds to form an antibody molecule |
| back 79 Heavy (H) Chains
two chains of an antibody that are identical to each other and contain more than 400 amino acids each. |
| back 80 Light (L) Chains
two chains of an antibody that are identical to each other, but they are only about half as long as each H chain. |
| back 81 Binding Site In each arm of the monomer, the V regions of the heavy and light chains combine shaped to “fit” a specific antigenic determinant. |
| back 82 C-Region
These are the effector regions of the antibody that dictate
1. the cells and chemicals of the body the antibody can bind to
2. how the antibody class functions in antigen elimination. |
| back 83 Monoclonal Antibodies
used in research, clinical testing, and treatment. |
| back 84 Hybridomas
fused tumor cells and B lymphocytes |
| back 85 Neutralization
the simplest defensive mechanism, occurs when antibodies block specific sites on viruses or bacterial exotoxins (toxic chemicals secreted by bacteria). As a result, the virus or exotoxin loses its toxic effect because it cannot bind to receptors on tissue cells to cause injury. The antigen-antibody complexes are eventually destroyed by phagocytes. |
| back 86 Agglutination
cell-bound antigens are cross-linked, the process causes clumping, |
| back 87 Precipitation
soluble molecules (instead of cells) are cross-linked into large complexes that settle out of solution. |
front 88 Complement fixation and activation | back 88 Complement fixation and activation
is the chief antibody defense used against cellular antigens, such as bacteria or mismatched red blood cells. When several antibodies bind close together on the same cell, the complement-binding sites on their stem regions align. |
front 89 Antibodies PLAN of Action | back 89 Antibodies PLAN of Action
precipitation, lysis (by complement), agglutination, and neutralization. |
| back 90 Class I MHC proteins
are displayed by virtually all body cells except red blood cells and are recognized by cytotoxic (CD8) T cell |
| back 91 Class II MHC proteins
typically found only on the surfaces of cells that present antigens to CD4 cells: dendritic cells, macrophages, and B cells. |
| back 92 Cytokines
a general term for mediators that influence cell development, differentiation, and responses in the immune system. |
| back 93 Endogenous Antigen
a bit of a cellular (self) protein or a peptide derived from a foreign protein synthesized in a body cell. |
| back 94 CD4+ T cells
T helper cell (TH cells) assist other white blood cells in immunologic processes, including maturation of B cells into plasma cells and memory B cells, and activation of cytotoxic T cells and macrophages. They express the CD4 protein on their surface. |
| back 95 CD8+ T cells
Cytotoxic T cells (TC cells, or CTLs) destroy virally infected cells and tumor cells, and are also implicated in transplant rejection. They express the CD8 glycoprotein at their surface. |
| back 96 Memory T cells
are a subset of antigen-specific T cells that persist long-term after an infection has resolved. They quickly expand to large numbers of effector T cells upon re-exposure to their cognate antigen, thus providing the immune system with "memory" against past infections. Memory T cells comprise two subtypes: central memory T cells (TCM cells) and effector memory T cells (TEM cells). |
| back 97 Regulatory T cells
(Treg cells) are crucial for the maintenance of immunological tolerance. Their major role is to shut down T cell-mediated immunity toward the end of an immune reaction and to suppress auto-reactive T cells that escaped the process of negative selection in the thymus. |
| back 98 Natural killer T cells
(NKT cells) bridge the adaptive immune system with the innate immune system. |
| back 99 Autografts
tissue grafts transplanted from one body site to another in the same person. |
| back 100 Isografts
grafts donated to a patient by a genetically identical individual, the only example being identical twins. |
| back 101 Allografts
grafts transplanted from individuals that are not genetically identical but belong to the same species. |
| back 102 Xenografts
grafts taken from another animal species, such as transplanting a baboon heart into a human being. |
| back 103 Immunodeficiency
Any congenital or acquired condition that causes immune cells, phagocytes, or complement to behave abnormally |
| back 104 Hodgkin’s disease
a cancer of the B cells, can lead to immunodeficiency by depressing lymph node cells. |
front 105 Acquired Immune Deficiency Syndrome (AIDS) | back 105 Acquired Immune Deficiency Syndrome (AIDS)
which cripples the immune system by interfering with the activity of helper T cells.Cripples the immune system by destroying helper T cells
• Characterized by severe weight loss, night sweats, and swollen lymph nodes
• Opportunistic infections occur, including pneumocystis pneumonia and Kaposi’s sarcoma
• Caused by human immunodeficiency virus (HIV) transmitted via body fluids—blood, semen, and vaginal secretions
• Treatment with antiviral drugs
• Incurable, and massive infection or cancer kills the sufferer |
front 106 HIV (human immunodeficiency virus) | back 106 HIV (human immunodeficiency virus)
destroys TH cells, depressing cell-mediated immunity. Although B cells and TC cells initially mount a vigorous response to viral exposure, in time a profound deficit of B cell and cytotoxic T cell function develops. The whole immune system is turned topsy-turvy. |
| back 107 Autoimmune Diseases
Occasionally the immune system loses its ability to distinguish friend (self) from foe (foreign antigens). When this happens, the artillery of the immune system, like friendly fire, turns against itself. The body produces antibodies (autoantibodies) and cytotoxic T cells that destroy its own tissues. |
| back 108 Multiple sclerosis
which destroys the myelin of the white matter of the brain and spinal cord (see p. 405) |
| back 109 Myasthenia gravis
which impairs communication between nerves and skeletal muscles (see p. 285) |
| back 110 Graves’ disease
which prompts the thyroid gland to produce excessive amounts of thyroxine (see p. 611) |
front 111 Type 1 (insulindependent) diabetes mellitus | back 111 Type 1 (insulindependent) diabetes mellitus
which destroys pancreatic beta cells, resulting in a deficit of insulin and inability to use carbohydrates |
| back 112 Systemic lupus
erythematosus (SLE), a systemic disease that particularly affects the kidneys, heart, lungs, and skin |
| back 113 Glomerulonephritis
a severe impairment of renal function |
| back 114 Rheumatoid arthritis
which systematically destroys joints |
| back 115 Hypersensitivities
allergies, Immune responses to a perceived (otherwise harmless) threat (usually involves haptens) |
| back 116 Allergen
is an antigen that causes an allergic reaction. |
| back 117 Anaphylactic Shock
typically occurs when the allergen directly enters the blood and circulates rapidly through the body, as might happen with certain bee stings or spider bites. It may also follow injection of a foreign substance (such as penicillin or other drugs which act as haptens). Essentially the same as that of local responses, but when mast cells and basophils are enlisted throughout the entire body, the outcome is life threatening. |
front 118 Subacute Hypersensitivities | back 118 Subacute Hypersensitivities
caused by antibodies (IgG and IgM rather than IgE) and can be transferred via blood plasma or serum. However, their onset is slower (1–3 hours after antigen exposure) and the duration of the reaction is longer (10–15 hours). |
front 119 Cytotoxic (type II) Reactions | back 119 Cytotoxic (type II) Reactions
occur when antibodies bind to antigens on specific body cells and subsequently stimulate phagocytosis and complement-mediated lysis of the cellular antigens. |
| back 120 Immune
Complex (type III) Hypersensitivity - results when antigens are widely distributed through the body or blood and the insoluble antigen-antibody complexes formed cannot be cleared from a particular area. |
front 121 Delayed Hypersensitivity (type IV) Reactions | back 121 Delayed Hypersensitivity (type IV) Reactions
are slower to appear (1–3 days) than antibody-mediated hypersensitivity reactions. The mechanism is basically that of a cell-mediated immune response, which depends on helper T cells. Inflammation and tissue damage comes about through the action of cytokineactivated macrophages, and sometimes cytotoxic T cells. |
front 122 Allergic Contact Dermatitis | back 122 Allergic Contact Dermatitis
which follow skin contact with poison ivy, some metals (nickel in jewelry), and certain cosmetic and deodorant chemicals. These agents act as haptens, and after diffusing through the skin and attaching to self-proteins, they are perceived as foreign by the immune system. |