AP BIOLOGY

Detailed explanation-1: -clonal selection: An hypothesis which states that an individual lymphocyte (specifically, a B cell) expresses receptors specific to the distinct antigen, determined before the antibody ever encounters the antigen. Binding of Ag to a cell activates the cell, causing a proliferation of clone daughter cells.

Detailed explanation-2: -When an antigen encounters the immune system, its epitopes eventually will react only with B-lymphocytes with B-cell receptors on their surface that more or less fit and this activates those B-lymphocytes. This process is known as clonal selection.

Detailed explanation-3: -Vaccination (immunization) is a way to trigger the immune response. Small doses of an antigen, such as dead or weakened live viruses, are given to activate immune system “memory” (activated B cells and sensitized T cells). Memory allows your body to react quickly and efficiently to future exposures.

Detailed explanation-4: -T cells can wipe out infected or cancerous cells. They also direct the immune response by helping B lymphocytes to eliminate invading pathogens. B cells create antibodies. B lymphocytes, also called B cells, create a type of protein called an antibody.

Detailed explanation-5: -For T cell activation to be initiated, two signals are required: TCR recognition of MHC class II peptide and a simultaneous costimulatory signal delivered by the same APC. If both signals are received, the T cell goes into the G1 phase of the cell cycle and begins to produce interleukin-2 (IL-2).