Chapter 7.3/7.4 Acquired Defenses Flashcards
If innate defenses have failed to prevent infection what is the next line of defense?
Acquired defenses. They overcome an infection by doing away with the particular disease causing agent that has entered the body. Also protect us against cancer.
How to acquired defenses work?
They respond to large molecules, normally protein structures, called antigens that the immune system recognizes as foreign to the body.
What can be considered antigenic?
Fragments of bacteria, viruses, molds, or parasitic worms, abnormal plasma membrane proteins produced by cancer cells can all be antigenic.
What do the acquired defenses primarily depend upon?
The action of lymphocytes, which differentiate as either B cells (B lymphocytes) or T cells (T lymphocytes).
What is the action of the lymphocytes T cells and B cells?
B cell and T cells are capable of recognizing antigens because they have specific antigen receptors. These antigen receptors are plasma proteins whose shape allows them to combine with particular antigens. Each lymphocyte has only one type of receptor. We need a diversity of B cells and T cells to protect us against the million different antigens. This diversification occurs during the maturation process. Millions of specific B cells/ or T cells are formed.
B cells differentiate into other types of cells, and so do T cells, What are they?
B cells: Produce Plasma cells and memory cells
Plasma cells
Plasma Cells: Produce specific antibodies
Memory Cells: Ready to produce antibodies in the future
T cells: Regulate immune response; produce cytotoxic T cells and helper T cells
Cytotoxic T cells:kill virus-infected cells and cancer cells
Helper T cells:regulate immunity
Memory T cells: ready to kill in the future
What is the B cell receptor and the clonal selection model?
The receptor on a B cell is called a B-cell receptor (BCR). The clonal selection model states that an antigen selects, then binds to the BCR of only one type B cell. Then this B cell produces multiple copies of itself. The resulting group of identical cells is called a clone. An antigen can bind to a T-cell receptor (TCR) and this T cell will clone.
What happens during clonal expansion?
During clonal expansion, cytokines secreted by helper T cells stimulate B cells to clone.
What do most of the cloned B cells become?
Plasma cells. They circulate in the blood and lymph. Plasma cells are larger than regular B cells because they have extensive rough endoplasmic reticulum. This is for the mass production and secretion of antibodies to a specific antigen. Antibodies identical to the BCR of the activated B cell are secreted from the plasma B cell.
What do some cloned B cells become?
Memory cells. The means by which long-term immunity is possible. If the same antigen enters the system again, memory B cells quickly divide and transform into plasma cells.
What happens once an infection as passed?
The development of new plasma cells ceases and those present undergo apoptosis, which is the process of programmed cell death. It involves a cascade of specific cellular events leading to the death and destruction of the cell and removal of the cells remnants from the body as a waste product.
What is defense by B cells called?
Humoral immunity or antibody-mediated immunity. Because activated B cells become plasma cells that produce antibodies.
What are the characteristics of B cells?
Antiboy-mediated immunity against pathogens, produced and mature in bone marrow, directly recognize antigen and then undergo clonal selection, clonal expansion produces antibody-secreting plasma cells as well as memory B cells.
What is the structure of an antibody?
The basic unit that composes antibody molecules is a Y-shaped protein molecule with two arms. Each arm as a heavy long polypeptide chain and a light short polypeptide chain. The chains have constant regions, located at the trunk of the Y, where the sequence of amino acids is fixed. Antibodies may consist of single Y shaped molecules called monomers, or may be paired together in a molecule termed a dimer.
What can antigens be part of?
A pathogen, such as a virus or toxin like that produced by tetanus bacteria.
