In order to become activated, these cells use their TCRs and CD8 molecules to bind to dendritic cells with MHC-I molecules with attached epitope on their surface. These cells capture and present protein antigens to effector T4-lymphocytes. When the MHC-II molecules with bound peptide on these cells are recognized by complementary shaped T-cell receptors (TCR) and CD4 molecules on a T(h)1-lymphocyte, the cell becomes activated and able to destroy intracellular pathogens. These cells are derived from T-lymphocytes and develop anamnestic response for heightened future response to the initiating antigen. These cells develop from B-lymphocytes and secrete vast quantities of antibodies. These cells interact with MHC-II molecules with bound epitope on the surface of activated B-lymphocytes and secrete cytokines which stimulate the proliferation and differentiation of these B-lymphocytes. a. T4-effector cells b. plasma cells c. macrophages d. T-memory cells e. naïve T8-lymphocytes 75. activated and able to destroy intracellular pathogens. 76. These cells are derived from T-lymphocytes and develop anamnestic response for heightened future response to the initiating antigen. 77. These cells develop from B-lymphocytes and secrete vast quantities of antibodies. 78. These cells interact with MHC-II molecules with bound epitope on the surface of activated B-lymphocytes and secrete cytokines which stimulate the proliferation and differentiation of these B-lymphocytes a. T4-effector cells b. plasma cells c. macrophages d. T-memory cells e. naïve T8-lymphocytes
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T cells are stimulated by the binding of antigen-MHC complex to the T cells' receptors. The outcome of this interaction (i.e., whether it leads to formation of antibodies or to the death of the cell with the antigen-MHC complex) depends on a. which class of MHC protein is involved. b. which type of T cell is involved. c. whether perforin is produced. d. All of the above e. None of the above Which immune protein(s) below is/are correctly described? Select all that apply: a. Antibodies: bind to specific epitopes, or molecular patterns, present on antigens. Antibodies comprise the B cell receptor. Secreted antibodies produced by plasma cells enable opsonization and agglutination b. Major histocompatibility complex (MHC): MHC II is present on professional antigen presenting cells (APCs) and present antigens to the T cell receptor (TCR) of T helper cells. MHC I is present on most nucleated cells and can present self-antigens as well as internal pathogen antigens to the T cell receptor. c. T cell receptor (TCR): membrane receptors on T cells that enable these lymphocytes to bind to epitopes presented by MHC molecules. Involved in the activation of T cells. d. Complement: innate immune system protein. Cascade of activation that enables the binding to invading microorganisms and promotes opsonization (phagocytosis) by phagocytic cells. e. Cytokines: small signaling proteins produced by various cell types. Involved in the activation and proliferation of B and T lymphocytes
Md.Daniyal A.
43. MHC molecules are required for a. B-cell activation. b. T-cell activation. c. phagocytosis of microbes. d. proteasome degradation of viruses. 44. The figure shown below illustrates a bacterial cell that Nucleic acids, lipids, polysaccharides, and proteins are released after phagocytosis a. acts as an antigen. b. is broken down into many antigens. c. is producing antibodies in response to antigens. d. has a single epitope. 45. An antigen-presenting cell (APC) presents antigen to a. macrophages to stimulate the synthesis of antibodies. b. B cells to stimulate the formation of memory B cells. c. memory T cells to stimulate the synthesis of cytokines. d. helper T cells to activate the T cells during a cellular response. 46. Which of the following would be expected to elicit the largest production of antibodies? a. haptens floating freely within plasma b. a complex protein with many different epitopes c. a polysaccharide with several identical segments d. a small lipid 47. An injection of killed or attenuated Salmonella typhi, the causative agent of typhoid fever, would be expected to protect an individual by a. causing the individual to have a mild case of typhoid fever, but protecting against future cases of typhoid fever. b. providing antigens recognizable by the immune system, allowing the formation of memory cells that will prevent typhoid fever in the future. c. providing cross-protection to prevent several diseases caused by different bacteria. d. providing the individual with premade antibodies capable of binding to and inactivating Salmonella typhi. 48. When comparing the primary and secondary immune responses, ______ titer levels are ______ during a ______ immune response. a. IgM; much higher; secondary b. IgG; much higher; secondary c. IgM; higher than IgG titer levels; primary d. IgM; higher than IgG titer levels; secondary 49. Class switching is the process in which a. B cells switch from producing IgM of IgD to producing IgE, IgG, or IgA. b. formed IgM antibody pentamers break apart into IgM monomers. c. antibody released from the surface of a B cell switches to a different heavy chain. d. higher-affinity antibodies are produced upon repeated exposure to the same antigen. 50. Why are cytotoxic T (Tc) cells more effective than antibodies at clearing viral infections? a. Tc cells are able to recognize free viral particles as they circulate through lymph nodes. b. Antibodies bind weakly to antigen-MHC I complexes on antigen-presenting cells. c. Antibodies are only able to bind to extracellular antigen, and viruses tend to be intracellular. d. Tc cells are activated more strongly than B cells by cytokines released by helper T cells.
Josee P.
Antibodies are produced by B cells, lymphocytes that are created and mature in red bone marrow. The function of these cells is to migrate to lymphoid tissue such as the spleen or lymph nodes and secrete protective antibodies in response to infection. When an antigen-presenting cell, like a B cell, makes contact with an antigen that can combine with its particular receptor, the APC and antigen bind. The APC then internalizes the antigen and digests it. Next, the APC displays digested antigen fragments on its surface by combining them with its major histocompatibility complex (MHC). The MHC is a collection of glycoproteins embedded in the plasma membrane. Class I MHC is found on all mammalian nucleated cells. Their presence identifies a cell as "self," preventing the immune system from making antibodies that would be harmful to our own tissues. Class II MHC is found on APCs (B cells, macrophages, and dendritic cells). Displaying antigen fragments bound to its MHC class II molecules attracts the appropriate T helper cell to the B cell. The TH cell makes contact with the fragment presented on the APC, and then the T helper cell produces cytokines that activate a B cell, which divides into a large clone of cells, including antibody-producing plasma cells and long-lived antibody cells. This antigen is known as a T-dependent antigen because it requires a TH cell to activate the B cell. T-independent antigens stimulate B cells directly, without the help of T cells. T-independent antigens tend to be molecules consisting of repeating subunits, such as polysaccharides or lipopolysaccharides. Bacterial capsules are a common example of T-independent antigens. These repeating units can bind to multiple B cell receptors, activating the B cell. These antigens tend to provoke a weaker immune response and do not produce memory cells. Question 6: Place the steps of B cell activation and antibody production in order chronologically for a T-dependent antigen. I - Antigen fragments are displayed on the B cell surface, attracting a matching T helper cell. II - The activated B cell begins producing antibodies. III - Antigen is phagocytized and digested. IV - APC receptors recognize and attach to antigen. V - T helper cell secretes cytokines, activating a B cell.
Shaiju T.
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