BMS 100 - Chapter 14 Outline: Immunity

---

Outlines | Home

---

Lymphocytes
1. Lymphocytes are one type of leukocyte (WBC). They originate in red bone marrow.
2. B cells are lymphocytes that mature while still in red bone marrow.
3. T cells are lymphocytes that travel to the thymus and mature there.
4. Most T cells and B cells eventually reside in lymphatic organs (lymph nodes, spleen, tonsils, etc.).

Antigens
1. Antigens are molecules that stimulate lymphocytes to respond.
   • "specific immunity" - the lymphocyte response targets only the specific type of antigen that triggered the response
2. Antigen inventory: before birth, the body makes an inventory of proteins and other large molecules in the body.
3. Any protein that is present during the inventory is considered "self."
4. Any protein that is not present during the inventory is, by default, "not self" and therefore considered "foreign" or abnormal.
   • "not self" molecules function as foreign antigens
5. B cells and T cells have the ability to distinguish between “self” and “not self.”
6. Two major types of specific immunity
   1. antibody-mediated immunity (AMI) - provided by B cells; results in production of antibody molecules that are effective against smaller antigens (viruses, bacteria, and toxins) in body fluids
   2. cell-mediated immunity (CMI) - provided by T cells that directly counteract antigen-bearing cells (some tumor cells, virus-infected cells, etc.)

T cells and CMI
1. a specific T cell is "activated” by a specific antigen
2. the activated T cell begins to divide repeatedly by mitosis, forming a T cell clone
3. some cells in the T cell clone
   1. cytotoxic T cells (“killer T cells”) recognize and destroy "target cells" (cells that bear antigen identical to that which triggered the process)
      • killer T cells destroy target cells by creating holes in their membranes and destroying their DNA
   2. memory T cells remain in the body after the antigen has been destroyed

B cells and AMI
1. a specific B cell is “activated” by a specific antigen
2. the activated B cell proliferates by mitosis and forms a clone
   • "helper T cells" (CD4 cells) are very important for proper development of B cell clones
3. cells in the B cell clone
   1. plasma cells - produce antibodies
   2. memory B cells – begin to produce antibodies but do not release them; memory B cells remain in the body after the antigen has been removed
4. Each antibody molecule can bind only with the specific type of antigen that triggered its production.
   
   
   
   
5. Antibody actions (mode of action depends on antigen):
   • Antibodies may neutralize toxins, viruses, etc. (prevents them from interacting with host cells).
   • Antibodies may cause agglutination (clumping together) of cells bearing the antigen (prevents them from spreading).
   • Opsonization: antibodies attached to a bacterium, etc., may make the bacterium more susceptible to phagocytosis.
   • Antibodies may activate complement (destroys membranes of foreign cells).

Primary and Secondary Immune Responses
1. The first response to an antigen is called the primary immune response.
   • "Lag period": several weeks may be required to generate clones of B cells and T cells.
   • Illness may occur during the lag period (not enough lymphocytes yet).
   • Clone includes "memory cells."
2. Any subsequent exposure to the same type of antigen prompts a secondary immune response.
   • secondary response is fast because memory cells already "know" the antigen
   • memory B cells begin releasing large numbers of antibodies within hours
   • illness is less likely
   • each exposure "fine tunes" the secondary response
   • vaccination (active immunization) - person receives "dead" or weakened antigen (goal is to cause production of memory cells)

---

Use on-line version of this outline to link to an excellent Immunity Animation

---

Chapter 14 Questions at OLC - 8, 9, 10, 11, 12, 13, 14, 16, 18, 19, 20, 21, 23, 24, 34, 35, 39, 40

---

Spring 2011