CH 21: IMMUNE SYSTEM- INNATIVE AND ADAPTIVE BODY DEFENSES

The immune system is a functional system that has three lines of defense that act

both independently and cooperatively to provide resistance to disease, or immunity.

Refer to Focus Figure 21.1 for a complete overview.

a. The ______ line of defense consists of surface barriers the skin and mucosae.

b. The _________ line of defense relies on innate internal defenses such as

antimicrobial proteins, phagocytes, and other cells that can attack both directly

and through recruitment of other defenses, often through the inflammatory

response.

c. The ______ line of defense is the adaptive (specific) defense system that

takes longer to initiate, requires recruitment, but is designed to recognize and

attack identified invaders.

FIRST, SECOND, THIRD

_______, a highly keratinized epithelial membrane, and mucous membranes represent a physical barrier to most microorganisms and their enzymes and toxins. 

SKIN

Protective chemicals of the epithelial tissues include___ to inhibit bacterial growth,______ (lysozyme) to destroy microorganisms, ______ to create sticky traps, ______ as antimicrobial peptides, and other specialized regional secretions. 

ACID, ENZYMES, MUCIN, DEFENSINS

_______, such as neutrophils and macrophages, confront microorganisms that breach the external barriers.

PHAGOCYTES

Phagocytes must be able to adhere to a pathogen before it can engulf it; to counteract this, pathogens are coated with complement proteins called ________. 

OPSONINS

_______ and macrophages destroy pathogens by engulfing them, acidifying the phagolysosome (pathogen-containing vesicles associated with a lysosome within the phagocyte), and digesting the contents with lysosomal enzymes. 

NEUTROPHILS

When phagocytes cannot ingest their targets, they may release chemicals lethal to pathogens. 

When phagocytes cannot ingest their targets, they may release chemicals lethal to pathogens

_______ cells are able to lyse and kill cancer cells and virally infected cells before the adaptive immune system has been activated, and they secrete chemicals that enhance the inflammatory response.

NATURAL KILLER (NK)

________ occurs any time the body tissues are injured by physical trauma, intense heat, irritating chemicals, or infection by viruses, fungi, or bacteria. 

INFLAMMATION

_______ is beneficial because it prevents the spread of damage, disposes of debris and pathogens, alerts the adaptive immune system, and sets up repair. 

INFLAMMATION

The four cardinal signs of acute inflammation are _____, ______, _____, and ____. 

REDNESS, HEAT, SWELLING, PAIN

Inflammation results from the release of inflammatory chemicals from damaged cells that cause vasodilation, and increased capillary permeability, which allows fluid containing clotting factors and antibodies to enter the tissues. 

Inflammation results from the release of inflammatory chemicals from damaged cells that cause vasodilation, and increased capillary permeability, which allows fluid containing clotting factors and antibodies to enter the tissues. 

Soon after inflammation, the damaged site is invaded by neutrophils and macrophages. 

1. Injured cells produce ________-inducing factors that induce neutrophils to enter the blood from the bone marrow, increasing their number. 

2. Inflamed endothelial cells produce C A M proteins that mark the cell—a process called_______

3. Continued signaling causes _______, in which neutrophils squeeze into the tissues between endothelial cells of the capillary walls. 

4. Inflammatory chemicals create chemical trails that encourage ______ of neutrophils and other W B C s into the site of damage. 

LEUKOCYTOSIS, MARGINATION, DIAPEDESIS, CHEMOTAXIS

______ proteins enhance the innate defenses by attacking microorganisms directly or by hindering their ability to reproduce.

ANTIMICROBIAL

______ are small proteins produced by virally infected cells that help protect surrounding healthy cells by causing synthesis of proteins that interfere with viral replication. 

INTERFERONS

_______ refers to a group of about 20 plasma proteins that provide a major mechanism for destroying foreign pathogens in the body. ** MEMBRANE ATTACK COMPLEX (MAC) 

• Three pathways by which complement can be activated are: the_____ pathway, involving antibodies to bind pathogens and complement; the ____ pathway, in which lectin proteins bind to sugars on the surface of the microorganism, and then bind to and activate complement; and the _____ pathway, triggered when complement factors interact on the surface of microorganisms. 

COMPLEMENT, CLASSICAL, LECTIN, ALTERNATIVE

____, an abnormally high body temperature, is a systemic response to microorganisms. 

FEVER

______ produced by leukocytes and macrophages act on the hypothalamus, causing a rise in body temperature. 

PYROGENS

There are ____ important aspects of the adaptive immune system: 

THREE

The adaptive defenses recognize and destroy the specific antigen that initiated the response. 

The adaptive defenses recognize and destroy the specific antigen that initiated the response. 

The immune response is a _____ response; it is not limited to the initial infection site.

SYSTEMIC

The immune system has memory; after an initial exposure, the immune response is able to recognize the same antigen and mount a faster and stronger defensive attack. 

The immune system has memory; after an initial exposure, the immune response is able to recognize the same antigen and mount a faster and stronger defensive attack. 

_____ immunity (anti-body meditated) is provided by antibodies produced by lymphocytes present in the body’s “humors” or fluids. 

HUMORAL

______ immunity (cell-meditated) is based on direct attack of microorganisms by lymphocytes and has living cells, rather than free proteins, as its protective factor. 

CELLULAR

______ are substances that can mobilize the adaptive responses and are the targets of all adaptive immune responses.

ANTIGENS

Complete antigens have ________, the ability to stimulate the proliferation of specific lymphocytes and antibodies, and _____, the ability to react with the activated lymphocytes and antibodies. 

IMMUNOGENICITY, REACTIVITY

_____ are incomplete antigens that are not capable of stimulating the immune response, but if they interact with proteins of the body, they may be recognized as potentially harmful. (WAITING FOR SOMETHING FOREIGN) 

HAPTENS

______ determinants are a specific part of an antigen that are immunogenic and bind to free antibodies or activated lymphocytes. 

ANTIGENIC

____-antigens are the body’s antigens that are not antigenic to itself, only to others, and are identified as “self” by  major histocompatibility complex (M H C) proteins on the surface of cells. 

SELF

The adaptive immune system involves three types of cells: lymphocytes that mediate humoral immunity,_ lymphocytes that comprise the cellular aspect of adaptive immunity, and____-presenting cells (A P C s) that aid T cells in recognition of their antigens. 

B, T, ANTIGEN

. Lymphocytes originate in the bone marrow and, when released, become immunocompetent and self-tolerant in either the thymus (__ cells) or the bone marrow (__ cells). 

T, B. 

Lymphocytes undergo selection in order to gain immunocompetence, the recognition of specific antigens, and__-tolerance, ensuring attack on the body’s own cells is prevented, by being subjected to: 

1. ______ selection, which allows only T lymphocytes that recognize M H C proteins to survive. 

2. _______ selection, which selects for T cells that do not recognize self-M H C proteins. 

SELF, POSITIVE, NEGATIVE

Immunocompetent B and T cells are exported from the _____ lymphoid organs, the thymus and bone marrow, to colonize the _______ lymphoid organs, such as the spleen and lymph nodes. 

PRIMARY, SECONDARY

The first encounter between a lymphocyte and antigens usually occurs in _____ lymphoid organs. 

1. Antigen binding with a particular lymphocyte selects that lymphocyte for further development, a process called clonal selection. 

SECONDARY

Once activated by ____ selection, a lymphocyte divides, producing an entire group of lymphocytes with an identical ability to bind to a given antigen. 

1. Most members of the clone become ______ cells that actively fight the infection. 

2. A few members of the clone become ______ cells that will respond quickly to future encounters with this antigen. 

CLONAL, PLASMA, MEMORY

Antigen-presenting cells (A P C s) are responsible for activating __ cells, by engulfing antigens and presenting fragments of these antigens on their surfaces, where they can be recognized by T cells. 

T

_______ cells are A P C s located on body surfaces that have contact with the external environment: They phagocytose antigens and migrate to lymphoid organs to present antigens to T cells. 

DENDRITIC

_______ are found throughout lymphoid organs and connective tissues and present antigens to T cells in order to be activated by T cells into aggressive phagocytes. 

MACROPHAGES

__ lymphocytes present antigens to helper T cells, in order to become more fully activated B cells. 

B

The immunocompetent but naive B lymphocyte is activated when ____ bind to its surface receptors. 

ANTIGENS

. The activated B lymphocyte begins ______ selection, the process of the B cell growing and multiplying to form an army of cells that are capable of recognizing the same antigen. 

CLONAL

Most cells of the clone develop into _____ cells, the antibody-secreting cells of the humoral response.

PLASMA

The cells of the clone that do not become plasma cells develop into _____ cells. 

MEMORY

The ____ immune response occurs on first exposure to a particular antigen, with a lag time of about 3–6 days. 

After mobilization, the antibody titer in the blood rises, peaking in about 10 days, and then declines to a low level. 

PRIMARY

The _________ immune response occurs when someone is exposed to the same antigen for a second time, and is a faster, more prolonged, more effective response. 

1. Mobilization of B cells takes only a few hours and rises to a much higher peak concentration after only 2–3 days, producing antibodies with a much higher binding affinity for the antigen that persists as immunologic memory for long periods. 

2. ____ humoral immunity occurs when the body mounts an immune response to an antigen. 

3. _______ acquired active immunity occurs when a person suffers through the symptoms of an infection. 

4. _______ acquired active immunity occurs when a person is given a vaccine. 

SECONDARY, ACTIVE, NATURALLY, ARTIFICIALLY

_______ humoral immunity occurs when a person is given preformed antibodies. 

1. ______ acquired passive immunity occurs when a mother’s antibodies enter fetal circulation. 

2. _______ acquired passive immunity occurs when a person is given preformed antibodies that have been harvested from another person. 

PASSIVE, NATURALLY, ARTIFICIALLY

_________ or immunoglobulins, are proteins secreted by plasma cells in response to an antigen that are capable of binding to that antigen. 

ANTIBODIES

The basic antibody structure consists of four looping polypeptide chains: two identical_____ (H) chains, and two identical, shorter, _____ (L) chains. 

1. Each chain has a variable region at one end, which serves as a variable antigen-binding site, and a constant region at the other end, which is nearly identical among all members of a given class of antibodies. 

HEAVY, LIGHT

Antibodies are divided into five classes based on their structure: I g ___, I g ____, I g , I g , ___ and I g ___. 

G, A, M, E, D

Antibody Targets and Functions 

1. _______ occurs when antibodies block specific sites on viruses or bacterial exotoxins, causing them to lose their toxic effects. 

2. ________ occurs when antibodies cross-link to antigens on cells, causing clumping. 

3. ________ occurs when soluble molecules are cross-linked into large complexes that settle out of solution. ** PHAGOCYTES 

4. ________ activation occurs when complement binds to antibodies attached to antigens and leads to lysis of the cell. 

NEUTRALIZATION, AGGULTINATION, PRECIPITATION, COMPLEMENT

There are two major populations of T cells, based on which of the cell differentiation glycoproteins the mature cell displays: CD__ cells and CD__ cells. 

4, 8

Activated CD__ cells usually become helper T cells that activate B cells, T cells, and macrophages; some become regulatory T cells that moderate the immune response. 

4

Activated CD__ cells become cytotoxic T cells that destroy cells or other foreign substances. 

8

Antigen presentation through the use of M H C (major histocompatibility complex) proteins is necessary for both activation and normal functioning of T cells.

Antigen presentation through the use of M H C (major histocompatibility complex) proteins is necessary for both activation and normal functioning of T cells.

Class__ M H C proteins are found on all body cells except R B C s and display antigens synthesized from within the cell or, if infected, the M H C s may also include fragments of foreign antigens. 

1

Class __ M H C proteins are antigens arising from outside the cell that are engulfed by the displaying cell. * TARGET CD4 

II

CD4 cells bind antigens only on class II M H C proteins; CD8 cells are activated by antigen fragments on class I M H C s, and may bind this antigen on any cell in the body. 

CD4 cells bind antigens only on class II M H C proteins; CD8 cells are activated by antigen fragments on class I M H C s, and may bind this antigen on any cell in the body. 

When__ cell antigen receptors bind an antigen, the cell must accomplish a double recognition process: It must recognize both the M H C protein and the antigen it displays. 

T

Following antigen binding, a T cell must bind one or more co-stimulatory signals present on the antigen-presenting cell. 

Following antigen binding, a T cell must bind one or more co-stimulatory signals present on the antigen-presenting cell. 

Once activated, a T cell enlarges and proliferates to form a clone of cells that differentiate and perform functions according to their T cell class. 

Once activated, a T cell enlarges and proliferates to form a clone of cells that differentiate and perform functions according to their T cell class. 

_______ are chemical signals, such as interferons and interleukins, secreted to amplify the immune response. 

CYTOKINES

______ T (Th) cells stimulate proliferation of other T cells and B cells that have already become bound to antigen.

HELPER

_______ T cells are the only T cells that can directly attack and kill other cells displaying antigen to which they have been sensitized, through the use of perforins and granzymes, or by triggering apoptosis of the target cell. ** SCAN SURFACES CALLED IMMUNE SURVEILLANCE 

CYTOTOXIC

________ T  (Treg) Cells either by direct inhibition, or by causing the release of cytokines, suppress the activity of both B cells and other types of T cells. ** INDUCE TOLERANCE 

REGULATORY

The goal of organ transplantation is to provide patients with a functional organ from a living or deceased donor. 

The goal of organ transplantation is to provide patients with a functional organ from a living or deceased donor. 

Transplant success depends on the similarity of the tissues because ______ T cells,___ cells, and _______ work to destroy foreign tissues. 

CYTOTOXIC, NK, ANTIBODIES

________, the most common type of transplant, are grafts transplanted from individuals of the same species. 

ALLOGRAFTS

___________ therapy following the transplant uses drugs to suppress rejection, but results in a weakened immune system. 

IMMUNOSUPPRESSIVE

An __________ is any congenital or acquired conditions that cause immune cells, phagocytes, or complement to behave abnormally. 

IMMUNODEFICIENCY

_________ syndrome is a congenital condition that produces a deficit of B and T cells. 

SCID (SEVERE COMBINED INMMUNODEFICIENCY)

___________ cripples the immune system by destroying helper T cells, and ultimately impairing T and B lymphocyte functioning. ** NO CURE 

1. AIDS is caused by the ______ virus which is transmitted in bodily secretions such as blood, semen, and vaginal secretions. ** NO CURE- BUT EFFECTIVELY MANAGED BY TREATMENTS 

AIDS (ACQUIRED IMMUNE DEFICIENCY SYNDROME), HIV (HUMAN IMMUNODEFIENCY)

_______ diseases occur when the immune system loses its ability to differentiate between self and nonself antigens, resulting in the production of autoantibodies and cytotoxic T cells that destroy its own tissues

AUTOIMMUNE

Autoimmune disorders are treated by suppressing the entire immune system, either by blocking cytokines, or co-stimulatory factors. 

Autoimmune disorders are treated by suppressing the entire immune system, either by blocking cytokines, or co-stimulatory factors. 

Failure of self-tolerance occurs when weakly self-reactive lymphocytes are activated when foreign antigens resemble self-antigens, or new self-antigens appear. 

Failure of self-tolerance occurs when weakly self-reactive lymphocytes are activated when foreign antigens resemble self-antigens, or new self-antigens appear. 

___________ result when the immune system causes tissue damage as it fights off a perceived threat that would otherwise be harmless. (TIME COURSE, ANTIBODIES/T CELLS INVOLVED?) 

HYPERSENSITIVITIES

_______ hypersensitivities (acute, or type I hypersensitivities), or allergies, begin within seconds after contact and last about half an hour. 

IMMEDIATE

The initial contact produces no symptoms, but sensitizes the individual to the allergen. 

The initial contact produces no symptoms, but sensitizes the individual to the allergen. 

Subsequent contact with the same allergen results in immediate binding of the allergen to I g E antibodies on mast cells and basophils, causing a release of histamine, and promotion of ________. 

INFLAMMATION

_______ hypersensitivities are caused by antibodies, take 1–3 hours to occur, and last 10–15 hours. 

SUBACUTE

Cytotoxic (_______) hypersensitivities occur when antigens bind to antigens on specific body cells and cause phagocytosis and complement-mediated lysis of cellular antigens. ** CASED BY IgM AND IgG 

TYPE II

Immune complex (_____) hypersensitivities result when antigens are widely distributed in the body, and form large numbers of insoluble antigen-antibody complexes that cannot be cleared from an area. 

TYPE III

Delayed (_____) hypersensitivity reactions are caused by T lymphocytes, activated when chemicals diffuse through the skin and bind to haptens, and can take 1–3 days to occur. 

TYPE IV