ch. 20 Flashcards
(14 cards)
Innate (nonspecific) system:
first line of defense: intact skin and mucous membranes; Additional defenses includes phagocytes (second line of defense);
Adaptive (specific) defense system (third line of defense):
works with the previous defenses, is an attack against particular foreign antigens by activated lymphocytes.
Innate (nonspecific) defenses:
Phagocytes: macrophages (develop from monocytes), neutrophils; process of phagocytosis.
Adaptive (specific) defenses:
Characteristics: antigen specific, has memory.
Humoral immunity (and targets)
- antibodies present in fluids
- targets- bacteria, toxins, free viruses.
Cell-mediated immunity (and targets)
- mediated by cells
- targets- cells, infected cells, cancer cells, transplant cells.
Antigens
- Most foreign molecules, esp. proteins
- A “foreign” molecule which can invoke the immune response
Cells of the immune system
- B cells
- T cells (LYMPHOCYTES)
Lymphocytes
- Formed in bone marrow
- become immunocompetent in either the bone marrow (B) or thymus (T).
- This involves the acquisition of a specific antigen receptor. Then dispersal to the secondary lymphoid organs such as lymph nodes, spleen. (See Figure 20.8.)
Humoral immune response
- activation of B cells by clonal selection.
- Antigen combines with surface receptor and stimulates the B cell to clone and develop into plasma cells and memory cells.
- Plasma cells secrete great amounts of antibodies that can combine with the antigen. -Memory cells result in a very rapid response for subsequent infections
primary vs. secondary response
primary- occurs on first exposure to to a particular antigen.
-typically has a lag period of 3-6 days after the antigen challenge.
secondary- faster, more prolonged, and more effective b/c immune system has already been primed to antigen, and sensory memory cells are in place “on alert’.
Cell-mediated immune response
Helper T cells stimulate T cell directed immune response
- cytotoxic T cells destroy infected or cancerous or foreign cells.
- Cytokines, such as the interleukins, are molecules that stimulate cells in the immune response.
Helper T cells–Roles?
- stimulating other T cells and B cells that are specific for the invading antigen.
- They secrete various interleukins to stimulate T cells and B cells.
- Because of the need for this stimulation, the helper T cell is essential for immune system function.
- HIV, the AIDS virus, destroys this cell type and so destroys a person’s immune system.
Cytotoxic T cells
- release of perforin to drill holes in target cells; then entrance of proteolytic enzymes (granzymes) that stimulate cell death (apoptosis).
- These T cells destroy virus-infected cells, cancer cells, and (unfortunately) transplanted organ cells.
