Exam 3 Review:  Chapter 21:  Immune Cells

macrophage - Any of the large long-lived phagocytic cells derived from monocytes comprising a major component of the diffuse immune system (sometimes called the reticuloendothelial system or, more recently, the mononuclear phagocytic system); macrophages from different sites have somewhat different properties; in addition to contributing to the killing of microorganisms and tumor cells; the release immune regulatory substances and play a vital role in antigen-presentation leading to the production of antibodies by B lymphocytes and the activation of T lymphocytes.

dendritic cell - An activated antigen-presenting cell (monocyte-derived wandering macrophage) responsible for induction of the primary antigen-specific immune response by their interactions with T and B lymphocytes; these wandering macrophages are usually found in the lymphoid organs such as the thymus, lymph nodes, and spleen; they are also found in the bloodstream and other tissues of the body; they account for less than one percent of mononuclear cells in the peripheral blood.

neutrophil = polymorphonuclear leukocyte - The most abundant type of granulocytic white blood cell (60-70% of total WBCs) which is the rapid responder to sites of injury and inflammation and is highly destructive of microorganisms, especially bacteria; its granules stain poorly and appear pale gray to lavender in typical blood stains; it is capable of phagocytosis and will participate in the removal of damaged tissues even in the absence of infection.

monocyte - The largest type of white blood cell (3-8% of total WBCs); a phagocytic agranulocyte, having a single well-defined, often kidney-bean shaped, nucleus and very fine granulation in the cytoplasm; they have long lifespans and when they emigrate into tissues they differentiate into various types of macrophages; they are slow responders to sites of injury and inflammation and are highly destructive of microorganisms.

B lymphocyte = B cell - A functional subclass of  lymphocytes, originating and maturing in the bone marrow; identified by the specific cell surface markers they express; they function in humoral immunity; they make antibodies = immunoglobulins in a complex process requiring lymphokine stimulation and reaction with a specific antigens, and usually the participation of antigen-presenting macrophages and T lymphocytes = T cells; when actively involved in immune defense they may transform into plasma cells; any one B lymphocyte makes only one specific antibody.

plasma cell - Any of the antibody-secreting (immunoglobulin-secreting) cells found in lymphoid tissue, and in small numbers in blood, red bone marrow, and other connective tissues; they are derived from B lymphocytes = B cells in a complex process requiring lymphokine stimulation and reaction with a specific antigen, and usually the participation of antigen-presenting macrophages and T lymphocytes = T cells; they are larger than ordinary B lymphocytes, with more cytoplasm, an eccentric nucleus, and sometimes patch of pale cytoplasm near the nucleus which represents a faintly visible enlarged and active Golgi apparatus where the antibodies are being packaged for storage and secretion.

memory B lymphocyte = memory B cell - A functional subclass of  B lymphocytes, which are produced after a B lymphocyte clone has become active in specific antibody = immunoglobulin production against a specific antigen; these cells are dormant during the initial response to antigen, but serve as rapid responders to any subsequent exposure of the individual to the specific antigen which was initially involved in their production; their presence insures that subsequent exposures to the specific antigen are met with a more rapid and powerful response; the majority of these cells will be found in the bone marrow and the secondary lymphatic organs.

T lymphocyte = T cell - A functional subclass of  lymphocytes, originating in the bone marrow and and maturing in the thymus; identified by the specific cell surface markers they express; (they do not make antibodies = immunoglobulins); they function in cellular immunity; they orchestrates and regulate many of the immune system's responses; several functional subcategories are recognized including memory T cells, helper T cells, suppressor T cells, cytotoxic T cells, and delayed hypersensitivity T cells; the majority of these cells will be found in the bone marrow and the secondary lymphatic organs.

helper T lymphocyte = helper T cell = T_h cell - A functional subclass of  T lymphocytes (identified by their CD4 markers), which are produced after an interaction with an antigen-presenting cell which has acquired and processed antigens; their activation causes them to release IL-2 and other signal molecules which provide "help," i.e., activate (cause proliferation and differentiation) of other lymphocytes (B, T_c, T_s, T_dh) capable of responding to the same antigen; they play the major role in coordinating antigen-specific immune responses; the majority of these cells will be found in the bone marrow and the secondary lymphatic organs.

cytotoxic T lymphocyte = cytotoxic T cell = T_c cell - A functional subclass of  T lymphocytes (identified by their CD8 markers), which are produced after an interaction with an antigen-presenting cell which has acquired antigens from a virally-infected host cell, a host cell infected by intracellular bacteria (e.g., mycoplasma) or from a tumor cell; their activation also requires IL-2 and other signals from a helper T cell; the activated T_c cells then migrate to the site of the infection or the tumor and secrete a variety of immune molecules, e.g., perforins, lymphotoxins, granzymes, and gamma interferon, which can lyse and kill or at least limit the growth of the targeted cells; these cells also play a major role in rejection of transplanted tissues and organs; the majority of these cells will be found in the bone marrow and the secondary lymphatic organs.

memory T lymphocyte = memory T cell - A functional subclass of  T lymphocytes, which are produced after a T lymphocyte clone has become active in some specific cell-mediated response against a specific antigen; these cells are dormant during the initial response to antigen, but serve as rapid responders to any subsequent exposure of the individual to the specific antigen which was initially involved in their production; their presence insures that subsequent exposures to the specific antigen are met with a more rapid and powerful response; the majority of these cells will be found in the bone marrow and the secondary lymphatic organs.

natural killer cell = NK lymphocyte = NK cell - A functional subclass of  lymphocytes, which are a resistance defense, i.e., not antigen-specific in their response; they are non-phagocytic cells which migrate to the vicinity of target cells (a host cell infected by a virus or an intracellular bacteria, e.g., mycoplasma, or a tumor cell), bind to the target cell and deliver a variety of potentially lethal chemicals; they may be assisted in identifying their target cells by the presence of antibodies bound to the target cell; these cells also play a major role in rejection of transplanted tissues and organs; the majority of these cells will be found in the bone marrow and the secondary lymphatic organs.  [Note:  these cells are sometimes referred to as "null" cells because they lack the CD markers which distinguish B and T lymphocytes.]

migration - The act of moving from one place to another; leukocytes are able to move from the red bone marrow, blood, lymph and lymphatic tissues, to any other tissues because they are capable of diapedesis (amoeboid movement); they often follow the concentration gradient of chemotactic signal molecules.

leukocytosis - An abnormally large increase in the number of white blood cells in the blood, often occurring during an acute infection or inflammation and also seen in many leukemias; generally a WBC > 11,000 cells/mm³ in adults, slightly higher in children.

List:

8. The types of disease against which cytotoxic T-cells are most effective.

           viral infections -- cancer (tumor cells) 

           [Note:  they also play a role in graft rejection and are responsible for certain types of allergies]

 Explain:

2. The differences between a natural killer (NK) lymphocyte and a cytotoxic T-Cell.

          The natural killer (NK) lymphocyte is a component of non-antigen-specific defenses; the NK lymphocytes have the capacity to attack a wide variety of "foreign things," usually virally-infected cells and tumor cells, and NK lymphocytes do not require any specific antigen exposure or antigen presentation in order to become active.

          The cytotoxic T_c lymphocyte is a component of antigen-specific defenses (within cell-mediated immunity); individual cytotoxic T_c lymphocytes have the capacity to attack a single specific "foreign thing," usually an antigenic determinant which is expressed as a cell membrane surface marker (or other cell membrane protein) on virally-infected cells and tumor cells, and cytotoxic T_c lymphocytes do require specific antigen exposure or antigen presentation in order to become active.

3. The process of clonal selection and differentiation of B Cells when they become activated by exposure to endogenous and exogenous antigen.

B lymphocytes mature in bone marrow and mature inactive B lymphocytes distributed throughout the lymphatic tissues of the body (and some circulate in the blood stream).  In a few instances, such as exposure to gram-negative bacteria, B lymphocytes can act directly in antigen processing and antigen presentation.  In most instances, however, macrophages must ingest and process foreign antigens and then patrol the lymphatic tissues in order to identify (by matching of the MHC Class II marker and the antigenic determinant) suitable T and B lymphocytes for antigen presentation.  In response to antigen-presentation, specific responsive B lymphocytes will be stimulated by regulatory substances (interleukins, cytokines, etc.).  This activation triggers cell division in the specific responsive B lymphocytes producing an increasing population (clone) of identical antigen-specific B lymphocytes.  The majority of the members of the clone begin antibody synthesis and secretion, transforming into plasma cells.  A minority of the members of the clone remain relatively dormant as potentially responsive antigen-specific memory B lymphocytes.  Later in the active response, plasma cells will differentiate into subclones which synthesize and secrete the different antibody classes, e.g., IgM, IgG, IgA, IgE, with all such antibodies still specific to the particular antigenic determinant. In brief, "clonal selection" is the identification of the subset of B lymphocytes responsive to a specific antigenic determinant through encounter with or antigen presentation with a particular antigenic determinant.  In brief, "differentiation" is the development of the subclones of active plasma cells and dormant memory B lymphocytes specific to a particular antigenic determinant.

4. The process of clonal selection and differentiation of T Cells when they become activated by exposure to endogenous and exogenous antigen.

T lymphocytes mature in the thymus and mature inactive T lymphocytes distributed throughout the lymphatic tissues of the body (and some circulate in the blood stream).  In a few instances, such as exposure to virally-infected cells and tumor cells, T lymphocytes can respond directly to antigen presentation by the altered self cell.  In most instances, however, macrophages must ingest and process foreign antigens and then patrol the lymphatic tissues in order to identify (by matching of the MHC Class II marker and the antigenic determinant) suitable T and B lymphocytes for antigen presentation.  In response to antigen-presentation, specific responsive T lymphocytes will be stimulated by regulatory substances (interleukins, cytokines, etc.).  This activation triggers cell division in the specific responsive T lymphocytes producing an increasing population (clones) of identical antigen-specific T lymphocytes.  Some members of the clone differentiate into helper Th and suppressor Ts lymphocytes.  A minority of the members of the clone remain relatively dormant as potentially responsive antigen-specific memory T lymphocytes.  Other responsive cytotoxic Tc lymphocytes will also develop into active clones. In brief, "clonal selection" is the identification of the subset of T lymphocytes responsive to a specific antigenic determinant through encounter with or antigen presentation with a particular antigenic determinant.  In brief, "differentiation" is the development of the subclones of active classes of T lymphocytes and dormant memory T lymphocytes specific to a particular antigenic determinant.