Workbook Blood And The Immune System (Page 6 of 8) in pdf

T cell lymphocytes are manufactured in the bone marrow and processed by

the thymus gland. They identify foreign substances. B cell lymphocytes

are manufactured in the bone marrow. They produce antibodies.

Macrophages are white blood cells found in the lymph nodes, blood, spleen,

or liver. They are involved in the second line of defence. They destroy

foreign invaders by phagocytosis; the invader is engulfed and destroyed by

enzymes within the macrophage. Lymphocytes are specialized white blood

cells involved in the third line of defence, including the production of

antibodies.

5. Explain how the following cells give immunity

T cells strengthen the immune response of B cells and they also directly

attack infected host cells. Helper T cells identify invaders by the antigen

markers on their membrane. Once the T cell has identified the invader, it

passes this information on to the B cell via lymphokine. The B cells divide

into clones. A second message is sent from the helper T cells, which

triggers the production of antibodies in the B cell. The most important

function of the B cells is to produce antibodies that bind to antigens to

fight infections. A B cell also provides immunity by turning into a memory

cell that can “remember” a foreign invader. These memory cells can

quickly attack if that same invader ever comes back. Killer T cells are

also activated by helper T cells. Killer T cells hunt for the invading

microbe and puncture the cell membrane of the invader. Killer T cells also

hunt for cells that have been infected by a virus. The killer T cells

destroy these infected cells, thereby preventing the virus from

reproducing.

6. How to antibodies defeat antigens? Describe FOUR contributions that

antibodies make to the immune system.

Antibodies are complementary to a specific antigen. By binding to it, they

create larger antibody–antigen complexes that leukocytes can “see” much

more easily. The complex can be more easily phagocytosed and cleared

away. Four contributions are (1) binding to antigens on bacteria, killing

them; (2) binding to poisons/toxins to prevent them from binding to cells;

(3) providing recognition for millions of possible antigens that the body

might encounter; and (4) binding to viruses to prevent them from entering

host cells.

Workbook Blood And The Immune System Page 6