Imunocompetent
Tolerance exists when the immune system does not respond to a particular antigen. All cells and tissues in the body contain antigens that normally do not stimulate an immune response. The immune system is said to exhibit tolerance toward such antigens.
the antigen must bind to the receptor
a condition in which the body of a sensitized person fails to respond to an antigen
B cells respond to the initial antigen challenge by producing progeny cells. The progeny cells include both memory cells and plasma cells.
Antibodies are secreted by a special group of white blood cells called lymphocytes. Each type of cell (including bacteria) has a unique protein on its cell membrane - an antigen. If a lymphocyte does not recognise a particular antigen, it will assume that the cell (or bacterium) is foreign and hostile. This is what antibodies respond to - the stimulus as the result of an unfamiliar cell. The antibodies attach to the antigens and kill the cell, or bacterium.
HBs antigen is an acronym for Hepatits B like antigens found in the blood cells They are the ones that assist the body to respond to any foreign antibody pertaining to that antigen.
Immunological memory is the ability of immune system to respond more rapidly and more effectively to pathogens that have been encountered previously and reflects the preexistence of a clonally expanded population of antigen specific lymphocytes.
To React
Helper T cells recognize the receptor-antigen complex and cause plasma and memory cells to be produced to then produce antibodies.
Adaptation/Evolution
It contains neither A antigen nor B antigen. their blood can be given to individuals of any other blood group red cells do not carry either A or B antigen and hence they do not react with their corresponding antibodies. Remember that an immune respond can only be trigger when the antigen is present in the blood. In another word the blood originally have no any antibody but upon antigen contact it will trigger the immune respond thus antibody is produced and agglutination of blood occur. for rhesus factor there are memory cell so the antibody is still present. That is why when an O blood group without any antigen and antibody (it have both antibody but it is not create yet as there is nothing to trigger its immune respond) can donate to AB group which has no antibody (which mean it will not be trigger by any blood group) but have both antigen (remember that all donated blood have no antibody as there is no immune respond to trigger it thus the AB blood with both antigen is fine; except rhesus factor if it have memory cell)
The class of immunoglobulin to respond to the fist exposure of an antigen is immunoglobulin class M (IgM). While Immunoglobulin G (IgG) would predominate on the second exposure.