Lymphatic System and Body Defenses Flashcards
Forms mechanical barrier that prevents entry of pathogens and other harmful substances into body.
Intact skin (epidermis)
Propel debris-laden mucus away from lower respiratory passages.
Cilia
Provides resistance against acids, alkalis, and bacterial enzymes.
Keratin
Form mechanical barrier that prevents entry of pathogens.
Intact mucous membranes
Systemic response triggered by pyrogens; high body temperature
inhibits multiplication of bacteria and enhances body repair
processes.
Fever
Filter and trap microorganisms and other airborne particles in nasal passages
Nasal hairs
Traps microorganisms in respiratory and digestive tracts.
Mucus
Group of plasma proteins that lyses microorganisms, enhances phagocytosis by opsonization, and intensifies inflammatory response.
Complement
Normally acid pH inhibits bacterial growth; urine cleanses the lower urinary tract as it flushes from the body.
Fluids with acid pH
Promote cell lysis by direct cell attack against virus-infected or
cancerous body cells; do not depend on specific antigen recognition.
Natural killer cells
Continuously lubricate and cleanse eyes (tears) and oral cavity
(saliva); contain lysozyme, an enzyme that destroys microorganisms.
Lacrimal secretion (tears); saliva
Inhibits growth of bacteria and fungi in female reproductive tract.
Acid mantle of vagina
Skin secretions make epidermal surface acidic, which inhibits
bacterial growth; sebum also contains bacteria-killing chemicals.
Acid mantle
Engulf and destroy pathogens that breach surface membrane
barriers; macrophages also contribute to immune response.
Phagocytes
Contains concentrated hydrochloric acid and protein-digesting
enzymes that destroy pathogens in stomach
Gastric juice
Contains concentrated hydrochloric acid and protein-digesting
enzymes that destroy pathogens in stomach
Gastric juice
Proteins released by virus-infected cells that protect uninfected tissue cells from viral takeover; mobilize immune system.
Interferons
Attached to B cell; free in plasma
IgM
When bound to B cell membrane,
serves as antigen receptor; first
Ig class released by plasma
cells during primary response;
potent agglutinating agent; fixes
complement.
IgM
Most abundant antibody in
plasma; represents 75–85%
of circulating antibodies
IgG
Some (monomer) in plasma;
dimer in secretions such as
saliva, tears, intestinal juice,
and milk
IgA
Believed to be cell surface receptor
of immunocompetent B cell;
important in activation of B cell.
IgD
Secreted by plasma
cells in skin, mucosae
of gastrointestinal and
respiratory tracts, and tonsils
IgE
Binds to mast cells and basophils
and triggers release of histamine
and other chemical mediators of
inflammation and some allergic
responses.
IgE
Main antibody of both primary
and secondary responses;
crosses placenta and provides
passive immunity to fetus; fixes
complement
IgG
Bathes and protects mucosal surfaces from attachment of
pathogens.
IgA
Believed to be cell surface receptor
of immunocompetent B cell;
important in activation of B cell.
IgD
Group of bloodborne proteins activated after binding to antibody-covered antigens; when
activated, complement causes lysis of the microorganism and enhances inflammatory
response.
Complement
Protein produced by a B cell or its plasma-cell offspring and released into body fluids
(blood, lymph, saliva, mucus, etc.), where it attaches to antigens, causing neutralization,
opsonization, precipitation, or agglutination, which “marks” the antigens for destruction
by phagocytes or complement.
Antibody (immunoglobulin)
Chemicals released by sensitized T cells, macrophages, and certain other cells:
Cytokines
inhibits” macrophage migration and keeps them
in the local area.
Migration inhibiting factor (MIF)—”
Helper factors
enhance antibody formation by plasma cells.
stimulates T cells and B cells to proliferate; activates NK cells.
Interleukin 2—
suppress antibody formation or T cell–mediated immune
responses (interleukin-10 transforming growth factor and others).
Suppressor factors—
—secreted by lymphocytes; helps make tissue cells resistant to
viral infection; activates macrophages and NK cells; enhances maturation of cytotoxic
T cells.
Gamma interferon—
attract leukocytes (neutrophils, eosinophils, and basophils) into
inflamed area.
Chemotactic factors—
Like perforin, causes cell killing; attracts granulocytes; activates T cells and macrophages.
Tumor necrosis factor (TNF)
Slows or stops the activity of B and T cells once the infection (or attack by foreign cells)
has been conquered. Thought to be important in preventing autoimmune diseases.
Regulatory T cell
A T cell that binds with a specific antigen presented by an APC; it stimulates the
production of other immune cells (cytotoxic T cells and B cells) to help fight the invader;
acts both directly and indirectly by releasing cytokines.
Helper T cell
Antibody-producing “machine”; produces huge numbers of the same antibody
(immunoglobulin); specialized B cell clone descendant.
Plasma cell
Lymphocyte that resides in the lymph nodes, spleen, or other lymphoid tissues, where it is
induced to replicate by antigen-binding and helper T cell interactions; its progeny (clone
members) form plasma cells and memory cells.
B cell
Activity enhanced by helper T cells; its specialty is killing virus-invaded body cells, as well
as body cells that have become cancerous; involved in graft rejection.
Cytotoxic T cell
Any of several cell types (macrophage, dendritic cell, B cell) that engulfs and digests
antigens that it encounters and presents parts of them on its plasma membrane for
recognition by T cells bearing receptors for the same antigen; this function, antigen
presentation, is essential for normal cell-mediated responses. Macrophages and dendritic
cells also release chemicals (cytokines) that activate many other immune cells.
Antigen-presenting cell
(APC)
Descendant of an activated B cell or T cell; generated during both primary and secondary
immune responses; may exist in the body for years thereafter, enabling it to respond
quickly and efficiently to subsequent infections or meetings with the same antigen.
Memory cell
Substance capable of provoking an immune response; typically a large, complex molecule
not normally present in the body.
Antigen
Perforin, granzymes—cell toxins released by cytotoxic T cells and NK cells.
Cytotoxins
chief antibody ammunition
used against cellular antigens
Complement fixation
cross-linking reaction in which
antigen-antibody complex settles out of solution
Precipitation:
antibody-antigen reaction that
causes clumping of cells
Agglutination:
antibodies bind to specific sites on
bacterial exotoxins or on viruses that can cause cell
injury
Neutralization
