Ch 43 DSM
In insects, which of the following is analogous to mammalian epithelial tissue, in that it serves as a first line of defense against infection?
A chitinous exoskeleton
Which of the following cell types carries out humoral immunity?
B cells
Someone infected by chicken pox as a child is unlikely to suffer from this disease a second time. This is due to immunological memory, a reservoir of what type of cells that were generated following the initial exposure?
Both T cells and B cells
Who is credited with performing the first documented immunization?
Edward Jenner
Which of the following classes of immunoglobins crosses the placenta and confers passive immunity to the fetus?
IgG Passive immunity refers to the immunity that is transferred from a pregnant mother to her fetus when IgG antibodies cross the placental barrier. Such immunity protects the fetus from pathogens to which it has never been exposed. IgM antibodies are too large to cross the placental barrier. IgE antibodies mediate allergic reactions, whereas IgA antibodies will only be passed to the fetus in the first breast milk. IgD antibodies are localized to the surface of B cells and do not cross into the placenta.
When searching for a donor for an organ transplant, doctors try to match the __________ of the donor and recipient as closely as possible.
MHC proteins MHC (major histocompatibility complex) molecules are cell surface molecules that bind antigens for subsequent processing by the immune system. With the exception of identical twins, the MHC molecules are different for every individual, ensuring that for organ transplants, some MHC molecules in the transplant will be foreign to the recipient. Thus, the goal is to match the MHC of donor and recipient as closely as possible. Cytokines are chemical signals released by activated macrophages, neutrophils, and helper T cells. Leucocytes are white blood cells. Blood type matching is more important for transfusions than organ transplantation because blood type is not unique to each individual.
Which of the following cells are part of the innate, second line of defense?
Macrophages After the first line of defense (skin or external barrier) is breached, the innate, or second line of defense, kicks in with macrophages performing phagocytosis on large invaders such as bacteria. Antimicrobial proteins and the inflammatory response are also part of this stage. Platelets play a role in blood clotting and are not part of the immune system. Prostaglandins are hormone-like fatty acids that increase, rather than decrease, inflammation. Both cytotoxic T cells and B cells are important in adaptive, not innate, immunity.
Besides helper T cells, what are two other types of cells that HIV infects?
Macrophages and brain cells
Which of the following cells does not play a role in immunity through the phagocytosis of pathogens?
Natural killer cells Instead, natural killer cells are a component of the innate cellular defenses in vertebrates. These cells circulate throughout the body and detect the abnormal surface proteins characteristic of some virus-infected and cancerous cells. Natural killer cells do not engulf stricken cells. Rather, they release chemicals that lead to cell death, thereby inhibiting further spread of the virus or cancer. The two main types of phagocytic cells in the mammalian body are neutrophils and macrophages. Neutrophils, which circulate in the blood, are attracted to signals from infected tissues and then engulf and destroy the infecting pathogens. Macrophages ("big eaters") are phagocytic cells that are larger than neutrophils. Some migrate throughout the body, whereas others reside permanently in organs and tissues, where they are likely to encounter pathogens. Dendritic cells mainly populate tissues, such as skin, that are in contact with the environment. They stimulate adaptive immunity against the pathogens they encounter and engulf them. In insects, immune cells called hemocytes travel throughout the body in the hemolymph, the insect circulatory fluid. Some hemocytes ingest and break down bacteria and other foreign substances.
Which of the following functions of plasma-cell secreted antibodies promotes phagocytosis of foreign bacteria?
Opsonization Antibodies do not kill pathogens directly: rather, they bind to antigens and "tag" them for inactivation or destruction by other mechanisms of the immune system. Opsonization is one such mechanism: antibodies bind to antigens on bacteria and form a structure that macrophages or neutrophils recognize as a target for phagocytosis. Neutralization refers to the binding of antibodies to viral, not bacterial, surface proteins. The membrane attack complex is formed by activated complement proteins: it creates pores in the membranes of the foreign cell that results in cell lysis.
Why is the development and distribution of a new flu vaccine required every year?
The influenza virus undergoes frequent mutations and evolves rapidly.
In a series of immune system experiments, the thymus glands were removed from baby mice. Which of the following would you predict as a likely result?
The mice readily accepted tissue transplants Mice that underwent thymectomy in infancy would not be able to produce functional T cells (remember, T cells are named for the thymus, which is the site of T cell "education"). As a result, they would be unable to reject transplanted tissue. Tissue is rejected in part as a result of the participation of T helper cells. The inflammatory response of these mice is the job of the innate, not the adaptive, immune system and would not be affected by thymectomy, nor would the likelihood of autoimmune disease, which usually results from the production of anti-self-antibodies. Cancerous tumors are more, not less, likely to develop in animals that have less active adaptive immunity.
Which statement describes what would most likely happen to microbes in the blood?
They are phagocytosed by macrophages in the spleen microbes in the blood are phagocytosed by macrophages in the spleen, an organ that traps circulating pathogens for destruction. Dendritic cells are part of the adaptive immune system. Eosinophils discharge destructive enzymes directed, particularly, against parasitic invaders. Natural killer cells do not engulf cells: they circulate throughout the body and detect abnormal proteins on the surface of certain viral-infected or malignant cells. Finally, neutrophils engulf and destroy pathogens in tissues.
Which of the following is not a disease caused by actions of the immune system?
all the above: Crohn's disease, Lupus, Ulcerative colitis, Rheumatoid arthritis
Histamine is an important signaling molecule in the immune system that directly triggers __________.
blood vessels to dilate and become more permeable The pain and swelling that alert you to a splinter under your skin are the result of a local inflammatory response and are changes brought about by histamine. Histamine is stored in densely packed vesicles of mast cells, which are found in connective tissue. The dilated capillaries at sites of damage, where histamine is released, leak fluid into neighboring tissues, causing localized swelling. Enhanced blood flow to the site helps deliver antimicrobial peptides. Antimicrobial peptides are short chains of amino acids that kill fungi and bacteria by disrupting their plasma membranes. Virus-infected body cells secrete interferons, which induce nearby uninfected cells to produce substances that inhibit viral replication. After receiving signals from helper T cells and interacting with an antigen-presenting cell, cytotoxic T cells use toxic proteins to kill cells infected by viruses or other intracellular pathogens before they fully mature. In response to multicellular invaders such as parasitic worms, eosinophils, which are often found beneath mucosal surfaces, discharge destructive enzymes. previous keep going
Lysozyme plays a role in immunity through _________.
breaking down bacterial cell walls
The proliferation of the B lymphocyte to which a specific antigen binds is referred to as __________.
clonal selection Clonal selection is the term used to describe the cell proliferation that follows antigen binding to a B or T cell. Such binding determines which lymphocyte will divide to produce a population of thousands of cells specific for the epitope on the antigen: these cells are identical clones of the initial challenged cell.
Our immune system does not usually attack our own healthy tissues because lymphocytes that target "self" tissue are __________.
destroyed or rendered nonfunctional T and B cells that target the body's own tissues are produced, but these lymphocytes are destroyed by apoptosis (programmed cell death) or rendered nonfunctional. The result of their elimination is the condition called self-tolerance. Such cells are not converted into other cell types.
Herpes simplex viruses, such as those that cause cold sores, can evade the immune system and persist in the body by __________.
infecting cells and then entering a largely inactive state Because the production of most viral proteins and free viruses eventually ceases, latent viruses do not trigger an adaptive immune response. Latency typically persists until conditions arise that are favorable for viral transmission or unfavorable for host survival, such as when the host is infected by another pathogen. Such circumstances trigger the synthesis and release of free viruses that can infect new hosts. Herpes simplex viruses remain latent in human sensory neurons, which, because they express relatively few MHC I molecules, are inefficient at presenting viral antigens to circulating lymphocytes. Stimuli such as fever, emotional stress, or menstruation reactivate these viruses to replicate from sensory neurons below the surface and to infect surrounding epithelial cells at the surface of the skin. Host lymphocytes are not destroyed, but they do become ineffective because of the latency of the virus in sensory neurons. Latent viruses persist in the nuclei of infected cells. Although they do not degrade host cell DNA, in some cases they integrate into the host genome. Some other viruses, such as the influenza virus, rapidly evolve as they replicate in one human host after another, undergoing frequent mutations.
Anaphylactic shock is a life-threatening condition in which __________.
inflammatory chemicals released from mast cells lead to an inability to breathe and a lack of blood flow This acute allergic response triggers constriction of bronchioles and sudden dilation of peripheral blood vessels, which causes a precipitous drop in blood pressure. Death can occur within minutes. Substances that can cause anaphylactic shock in allergic individuals include bee venom, penicillin, peanuts, and shellfish. People with severe hypersensitivities often carry syringes containing the hormone epinephrine. An injection of epinephrine rapidly counteracts this allergic response by constricting peripheral blood vessels, reducing swelling in the throat, and relaxing muscles in the lung to help promote breathing. In septic shock, certain bacterial infections induce an overwhelming systemic inflammatory response. Impairment of the immune system that occurs in acquired immunodeficiency syndrome (AIDS) leaves the body susceptible to infections and cancers that a healthy immune system usually defeats. Certain cancers, especially Hodgkin's disease, suppress the immune system, leading to damage to the lymphatic system. In a graft-versus-host reaction, lymphocytes in surgically transplanted tissue such as bone marrow react against the body of the recipient.
Passive immunity differs from active immunity in that passive immunity ___________.
is conferred by antibodies produced by another individual
Which of the following is not a characteristic of innate immunity?
its present only in vertebrates things that ARE true: It does not include a contribution from immune cells, It distinguishes self from nonself when searching for foreign molecules, It is a rapid response to potential infection, It includes barrier defenses
B lymphocytes __________.
multiply and make antibodies that circulate in blood and lymph Their primary job is to multiply by clonal selection when challenged by an antigen and to secrete antibodies that circulate in blood and lymph. Helper T cells stimulate other lymphocytes, whereas helper T cells and antigen-presenting cells produce cytokines. Macrophages engulf and destroy bacteria and viruses.
Herpes simplex viruses, such as those that cause cold sores, can evade the immune system and persist in the body by __________.
nfecting cells and then entering a largely inactive state
Which of the following is a specific mechanism by which antibodies function in immunity?
opsonization of bacteria, recruitment of natural killer cells to destroy virus-infected body cells, activation of complement system, neutralization of viruses
What role do major histocompatibility complex (MHC) molecules play in immunity?
presenting antigens to T cells Recognition of protein antigens by T cells begins when a pathogen or part of a pathogen either infects or is taken in by a host cell. Inside the host cell, enzymes cleave the antigen into smaller peptides. Each peptide, called an antigen fragment, then binds an MHC molecule inside the cell. Movement of the MHC molecule and the bound antigen fragment up to the cell surface results in antigen presentation, display of the antigen fragment in an exposed groove of the MHC protein. If the cell displaying the antigen fragment encounters a T cell with the right characteristics, the antigen receptor on the T cell can bind to both the antigen fragment and the MHC molecule, initiating participation of the T cell in the immune response.
Antibodies belong to which class of proteins?
receptor Antibodies are receptor proteins on B cells whose interaction with antigen stimulates the immune system to make soluble antibodies. They do not provide structure to the cell, nor do they affect the speed of chemical reactions or transport substances.
Vaccination led to the eradication of the disease ________.
smallpox
The idea behind vaccination is to induce __________ without requiring the vaccinated individual to get sick.
the primary immune response
In humans, the first line of defense against infection is __________.
the skin and mucous membranes
Which of the following organisms would produce antibodies as part of an immune response?
whale Whales, along with other vertebrates, are unique among animals in that they have both adaptive and innate immunity. The adaptive response relies on blood cells called lymphocytes, which include B cells that secrete antibodies. Each antibody binds to just one part of one molecule from a particular pathogen, such as a species of bacteria or a strain of virus. Antibodies then interfere with pathogen activity or designate pathogens in various ways for inactivation or destruction by other components of the immune system. Earthworms, lobsters, and spiders are invertebrates, animals that lack adaptive immunity and thus do not produce antibodies as part of an immune response.
