Immune System

Molecules and Cells  Molecules:  Antibodies (humoral immunity)  Complement proteins  Cells;  Phagocytes  Lymphocytes

Terms  Antigen: foreign proteins, on surfaces of invading pathogens or cancer cells, or any foreign cell entering the body.  Antibodies: protein compounds that are made in response to an antigen, unique shape  Allows for easy binding with antigens.

Functions  FUNCTIONS:  Antibody-mediated immunity (humoral immunity/antibody mediated immunity)  Antibody binds to antigen..antibody- antigen complex

Antigen-antibody Complexes  Lock and key  3 processes can occur when this complex is formed

one  Antibody binds to antigen and inactivates the antigen  The antigen can no longer produce the poisonous toxin

two  Antibody binds antigens together  clumped together (agglutinate) and more quickly  destroyed by the macrophages; a type of phagocyte  (large #’s at one time)

three  complex renders the antigen more  vulnerable for phagocytosis  promotes attachment of phagocytic cells

Complement proteins  Complement proteins: proteins circulating, normally inactive, become activated by exposure to antibodies  complement-binding sites are exposed

Complement Binding  complement: group of 14 proteins normally inactive in the blood  result: RAPID KILLING of invading cells  process: the protein antibody complex drills through the foreign cell’s membrane, causing  sodium to enter the cell (diffusion), followed by water (osmosis) Increased pressure causes the cell to lyse (lysis)

Immune System Cells (white blood cells)  Phagocytes  A. Neutrophils  B. Monocytes  C. Macrophages  Lymphocytes  A. T-lymphocytes  B. B-lymphocytes

Phagocytes  Made in bone marrow (hemopoeitic tissue)  Ingestion and digestion of foreign cells  Types:  Neutophils; short lived  Monocytes; develop into macrophages  Some macrophages take up residency in the tissues (Kupffer’s cells in liver and dust cells in lungs)

B-lymphocytes  Start as stem cells  Develop into immature B-cells that have antibodies in cell membrane  Migrate to lymphatic tissues (nodes, spleen)  Become activated by an antigen

Activated B-cells  Divide very quickly and makes many clones of self  Change into memory cells and plasma cells  Memory cells; stored in lymph nodes Remember the antigen Remember the antigen Plasma cells; secret antibodies into the blood Plasma cells; secret antibodies into the blood

T-lymphocytes  Start as stem cells  Changed into t-cells in thymus gland  Migrate to lymph nodes  sensitized by antigens  Cell mediated immunity  Kill directly or help gather foreign cells