Immune Physiology - Anatomy

B-lymphocytes are part of the adaptive immunity system, they create plasma cells and antibodies when they recognize a specific antigen. Monocytes are what macrophages are before they leave the bloodstream. Basophils contain granules of histamine which produce an inflammation response when released. Natural killer cells attack infected or cancerous cells.

Antibodies are produced by plasma cells (mature B-cells) with specific binding affinity for surface proteins that have been presented by antigen-presenting cells, like dendritic cells and macrophages. Once the plasma cell is stimulated by the presence of the specific antigen, it increases production of its antibody. These antibodies enter the blood and bind the antigen molecules on the surface of the pathogen cell. Cytotoxic T-cells and cytokines can then interact with the antibodies to initiate lysis of the infected cell or pathogen.

It helps to think of antigens and antibodies like a lock and key: they are highly specific for one another. B-lymphocytes create only one type of antibody. When this antibody attaches to an antigen presented by a macrophage or antigen-presenting cell, the B-lymphocyte will differentiate with the help of a helper T-cell. The result is replication of the B-lymphocyte to produce more of the same antibody from plasma cells and generate memory B-cells to easily respond in the event of a second infection by the pathogen.

The question specifies that the antibodies in question are serum antibodies, while IgA is primarily an antibody type secreted into luminal environments. As a result, we can conclude that IgA is not likely to be involved at all in this experiment. Beyond this, you must know that IgM is the type of antibody that is produced upon initial pathogen exposure. After CD4 cells facilitate isotype switching, IgG is produced and demonstrates more robust binding.

The epitope is the region of a target cell to which an antibody binds. The remaining choices are all structural regions of the antibody itself, as opposed to the target cells to which an antibody binds.

Skin is an innate external defense barrier and does not involve antibodies. Inflammation and antimicrobial proteins are innate internal defense mechanisms, and are not pathogen-specific. T-lymphocytes are adaptive cell-mediated defense mechanisms. The humoral system, though, is part of the adaptive immune system, which delivers antibodies through blood to fight antigens extracellularly.

IgG is the only class of immunoglobulin that is able to cross the placenta. This is important as this immunoglobulin is able to provide passive immunity to the unborn fetus

MHC I is found on all nucleated cells and presents antigens to cytotoxic T lymphocytes. These cytotoxic T cells contain CD8 receptors, which binds to MHC I. MHC II cells are found on B-lymphocytes and antigen presenting cells only. MHC II presents antigens to helper T cells, which contain CD4 receptors.

IgE is able to bind via the (fragment crystallizable) Fc region to mast cells and basophils. This binding allows these cells to release their granule contents involved in many allergic reactions.

IgM is the first antibody produced during the primary immune response. It is the only immunoglobulin whose shape is a pentamer. IgG is the most abundant immunoglobulin class in the blood and tissue and has the ability to cross the placenta. IgE binds to basophils and mast cells and is involved in the allergic response.

For any recipient, we must consider what antibodies they have. A patient with A positive blood has the following antibodies: anti-B For any donor, we must consider what antigens they have. The donor cannot have an antigen that matches the recipient's antibodies, or else agglutination will occur. Therefore, any B blood types will result in agglutination. The O positive person only expresses the Rh antigen, and the recipient does not express this antibody. No agglutination will occur.

An AB positive patient is known as a universal recipient because they can receive blood from any blood type. The recipient's antibodies are what will attack foreign antigens. Type AB positive patients produce no antibodies, because any antibody produced would attack their own antigens, causing agglutination. Because type AB patients patients do not produce antibodies, they cannot attack any antigens and they can receive any blood type.

A person with O negative blood is known as the universal donor because their blood cells completely lack antigens. This means their blood cannot be recognized as foreign by a donor. For blood transfusions, we must keep in mind the recipient's antibodies. For an O negative recipient, he/she produces A and B antigens, and Rh antigens if they have been previously exposed to Rh positive blood. That means they cannot accept blood from donors with A, B or possibly Rh positive blood. They must receive O negative blood only.

Rh negative people are not born with Rh antibodies. After exposure to Rh positive blood, the Rh negative patient will begin producing Rh antibodies. Any subsequent exposure will cause agglutination. This has applications in childbirth, if there mother is Rh negative, and the baby is Rh positive. It is possible for the baby's blood to come in contact with the mother's (especially during childbirth). Neither the baby nor the mother are at risk, however, if the mother has another baby that is Rh positive, the mother will have antibodies from when she first encountered Rh positive blood from the previous baby. This may cause harm to the second (and any subsequent) Rh positive babies.

Blood antigens are the protein markers on the surface of red blood cells. On an A positive red blood cell, there is the A marker (antigen) and the Rh marker (antigen). Antibodies are found in the blood plasma, and these bind to foreign antibodies to cause agglutination. People produce antibodies for the antigens they do not have (Rh antibodies are only made after exposure to Rh positive blood). An A positive person will express the B antibody.

Blood antigens are the proteins markers on the surface of a red blood cell. On an AB positive red blood cell, there is the A marker (antigen), the B marker (antigen) and the Rh marker (antigen). Antibodies are found in the blood plasma, and these bind to foreign antibodies to cause agglutination. People produce antibodies for the antigens they do not have (Rh antibodies are only made after exposure to Rh positive blood). An AB positive person will not have any antibodies, otherwise they would bind to their own red blood cells and cause agglutination.

We must first assume the two people are A, B, O compatible (ie., both patients are type A). An Rh negative person is negative because they lack the Rh antigen. An Rh positive person does not produce any Rh antibodies or else they would attack their own blood. Therefore, there is no antigen to attack and no antibodies to attack with, so agglutination will not occur.

Antibodies are part of humoral immunity. The humoral pathway protects against extracellular pathogens. Antibodies are produced and secreted by B lymphocytes (B cells). They recognize free antigens, initiate activation of other immune cells, and coat the antigen for destruction (which may or may not be cellular).

Plasma cells arise from B-lymphocytes. When a B-lymphocyte's antibody comes in contact with a matching antigen presented by a macrophage, the B-lymphocyte will differentiate into a plasma cell. The plasma cell will then release free antibodies into the blood which can then attach to the pathogens.

Memory B-cells remain latent in the body and differentiate into plasma cells upon reinfection by the same antigen. Neutrophils, macrophages, and monocytes have phagocytic properties that allow them to engulf and digest pathogens. Mast cells and basophils secrete histamine to stimulate the inflammatory response. Dendritic cells and some other cell types can present antigens to helper T-cells to initiate an adaptive immune response.

While humoral immunity and cell-mediated immunity play different roles in the immune system, both systems require helper T-cells. B-lymphocytes must interact with helper T-cells in order to differentiate into plasma and memory B-cells, initiating the humoral immune response. Helper T-cells are also necessary for activating cytotoxic and suppressor T-cells in cell-mediated immunity.

Basophils are not involved in adaptive immunity of any type; they are responsible for inflammation and certain other processes in innate immunity.