Exam 3 Review:  Chapter 21:  Specific Immunity

antigen - A substance that, when introduced into the body, stimulates the production of a specific antibody or a specific cell-mediated immune response; antigens include toxins, viruses, bacteria and other microorganisms, foreign blood cells, and the cells of transplanted organs and tissues; at the molecular level, antigens are large and complex molecules, usually proteins, less often carbohydrates or lipids, and only rarely nucleic acids.

antigenic determinant - A region on the surface of an antigen molecule to which a specific antibody or T lymphocyte receptor binds; at the molecular level, they are portions of the larger whole molecule, e.g., a cluster of adjacent amino acids on a protein or a cluster of monosaccharides (simple sugars) on a carbohydrate (polysaccharide).

antigen receptor - A specific molecule or complex of molecules on the surface of B and T lymphocytes which is capable of recognizing and non-covalently binding with a specific antigenic determinant; this binding is one of the necessary signals to begin activation of the lymphocytes; these binding sites are found as the variable regions of antibody molecules (immunoglobulins) and in the MHC Class II surface markers on T lymphocytes.

exogenous antigen - Any antigen which originated or is derived from outside the body; the vast majority of antigens to which the immune system responds because they are "foreign" to the individual, i.e., non-self.

endogenous antigen - Any antigen which originated or is derived from inside the body; this group includes ordinary self-antigens, including some which are unavailable for the lymphocyte-maturation process, e.g., sperm antigens which have not yet been produced at the time; it also includes some antigens which arise internally as a result of a disease process, e.g., the altered membrane lipids to which the reagin antibody forms in certain inflammatory processes including syphilis infection; it also includes many tumor antigens.

tumor antigen - Any antigen which originated or is derived from a cancer cell = tumor cell; while most such antigens are endogenous, a few are considered exogenous because the are derived from oncogenic viruses which have the capacity to transform host cells into tumor cells.

antibody-mediated immunity - The portion of the specific immune response which is due to the activation of B lymphocytes to differentiate and proliferate as clones of antibody-producing plasma cells and B memory cells.  [Note:  an older term for this process is humoral immunity.]

cell-mediated immunity - The portion of the specific immune response which is due to the activation of T lymphocytes to differentiate and proliferate as clones of helper, suppressor, and cytotoxic T cells and T memory cells.  [Note:  certain T lymphocytes (helpers and suppressors) also contribute to antibody-mediated immunity by their interactions with B lymphocytes.

List:

7. The two "arms" of adaptive (specific) immunity and the cells important in each.

Antibody-Mediated Immunity ("Humoral Immunity") Cell-Mediated Immunity
major cellular defender major cellular defenders
B lymphocytes which become active Ab-secreting plasma cells activated cytotoxic Tc cells and helper Th lymphocytes
additional significant participants additional significant participants
macrophages as antigen-presenting cells, helper Th lymphocytes, suppressor Ts lymphocytes and memory B lymphocytes macrophages as antigen-presenting cells, suppressor Ts lymphocytes and various classes of memory T lymphocytes

11. The differences between a first immune response and a second = memory response.

First Immune Response Second = Memory Response
(1)  The first response is the result of the individual's first encounter with the "foreign" antigen.

(2)  The first response shows a delay or lag time, typically of 2 to 5 days duration, which represents the time necessary for antigen-processing, antigen-presentation, activation of specific clones of responsive T and B lymphocytes, and time for them to proliferate by repeated mitoses into relatively large populations adequate to deal with the "foreign" antigen.

(3)  The strength of the first response is relatively low and somewhat limited.  For example, often only IgM class antibodies are elaborated in the first response.  At the end of the first response, circulating antibody levels drop back to negligible (though not zero) levels.

(1)  The second = memory response is the result of the individual's second or any subsequent encounter, even decades later, with the same "foreign" antigen.

(2)  The second = memory response shows a much reduced delay or lag time, typically from a few hours to a day or two in duration, which represents the time necessary for antigen-processing, antigen-presentation, activation of specific clones of responsive T and B memory lymphocytes, which already exist in relatively large numbers, though in a dormant state.

(3)  The strength of the second = memory response is much greater and more elaborate.  For example, not only will IgM class antibodies be elaborated, but also generally IgG class antibodies and possible IgA and IgE as well.  At the end of the second or any subsequent memory response, circulating antibody level drop back, but not to low/negligible levels and this background level of circulating antibody will persist for long periods, sometimes even for years or decades.

Describe:

2. The difference between nonspecific resistance to disease and specific resistance to disease, i.e., immunity.

Nonspecific Resistance To Disease Specific Resistance To Disease, i.e., Immunity
Those body defenses which are already in place and fully functional before the body is exposed to the disease-causing entity.  Examples include physical and physiological barriers (e.g., skin and mucous membranes), various chemical defenses (lysozyme, interferons, complement proteins, hyaluronic acid, fibrin, electrolytes, anti-bacterial fatty acids, etc.), and cells (granulocytic leukocytes, monocytes and monocyte-derived macrophages, and natural killer (NK) lymphocytes. Those body defenses which are already in place and but not fully functional before the body is exposed to the disease-causing entity and specific antigen presentation has occurred to activate the defenses.  Examples include B lymphocytes and plasma cells in antibody-mediated immunity and the various classes of T lymphocytes (helper, cytotoxic, suppressor, etc.) in cell-mediated immunity.

3. The two types of immune response (AMI versus CMI).

Antibody-Mediated Immunity ("Humoral Immunity") Cell-Mediated Immunity
Antibodies to specific antigenic determinants are secreted by plasma cells into the tissue fluid, lymphatic drainage, and blood circulation.  These antibodies are then widely distributed through all tissues and some are added to mucous secretions as well.  antibodies have a number of defensive functions.  First, they adhere to the antigen and this adherence may inactivate the antigen.  Secondly, they act as opsonins, encouraging phagocyte adherence and facilitating phagocytosis.  Thirdly, certain classes of antibodies, e.g., IgM, can act as triggers to unleash the complement cascade against the antigen.  Five classes of immunoglobulins are recognized, IgG, IgM, IgA, Igd, and IgE.  Typically Antigen-presentation by a macrophage and Th lymphocyte "help" is required to initiate antibody production. Cell-mediated immunity is a more diverse set of specific defensive responses.  Each response is provided by a different subset of T lymphocytes.  (1) helper Th lymphocytes play a major managerial/regulatory role in the postive feedback control systems which activate B lymphocytes and cytotoxic Tc lymphocytes (usually in cooperation with antigen-presenting macrophages), working to establish complementary clones which are all responsive to the same antigenic determinant.  (2)  cytotoxic Tc lymphocytes direct non-phagocytic attacks against virally-infected cells, tumor cells, multicellular parasites, and transplanted organs/tissues.  (3)  suppressor Ts lymphocytes play a managerial/regulatory role in the negative feedback control which damps down antigen-specific immune responses by T and B lymphocytes when the immune defense has been successful.

4. The difference between "self" and "foreign" antigens.

Self endogenous antigen - Any antigen which originated or is derived from inside the body; this group includes ordinary self-antigens, including some which are unavailable for the lymphocyte-maturation process, e.g., sperm antigens which have not yet been produced at the time; it also includes some antigens which arise internally as a result of a disease process, e.g., the altered membrane lipids to which the reagin antibody forms in certain inflammatory processes including syphilis infection; it also includes many tumor antigens.
Foreign exogenous antigen - Any antigen which originated or is derived from outside the body; the vast majority of antigens to which the immune system responds because they are "foreign" to the individual, i.e., non-self.

Sketch and label:

3. A diagram of the process of immunity.

Explain:

1. The difference between endogenous and exogenous antigen.

Self endogenous antigen - Any antigen which originated or is derived from inside the body; this group includes ordinary self-antigens, including some which are unavailable for the lymphocyte-maturation process, e.g., sperm antigens which have not yet been produced at the time; it also includes some antigens which arise internally as a result of a disease process, e.g., the altered membrane lipids to which the reagin antibody forms in certain inflammatory processes including syphilis infection; it also includes many tumor antigens.
Foreign exogenous antigen - Any antigen which originated or is derived from outside the body; the vast majority of antigens to which the immune system responds because they are "foreign" to the individual, i.e., non-self.