What is an Antigen?

• Antigen's are foreign molecules recognised by the immune system.
• Antigens can be protein, carbohydrate, lipid or nucleic acid molecules.
• Examples include viruses and bacteria as well as fragments of human cells such as those infected by a virus or damaged by radiation or oxidants.

Antigens also include artificial substances such as drugs and other xenobiotics (chemicals not normally capable of being taken up by living systems). Antigens are associated with different types of MHC molecule on the surface of cells which allows them to be identified by T lymphocytes.

Antibodies are Y shaped proteins produced by B lymphocytes in response to antigens binding to their antigen receptor on their cell membrane. Antibodies circulate through the blood stream and lymph fluid, where they find and bind their antigen, marking it for destruction by phagocytosis or antibody dependent cell mediated cytotoxicity. Antibodies can also be transported across the placenta to provide protection against antigens in the mother's circulation for the fetus.

Antibody molecules are highly specific to an antigen of choice due to their Y-shape. Antibody diversity is generated when lymphocytes with different receptors are produced through a process called V(D)J recombination . Antigen receptor genes rearrange randomly on both strands of DNA , leading to large numbers of potential antibody protein variations. This allows an almost unlimited number of different antibodies capable of binding any given antigen, since there are more possible permutations of the antibody combining site than there are atoms in the known universe.

Antibodies are released into the circulation, where they find their antigen and bind to it. Antigens can be found on host cells as well as invading pathogens, so both are destroyed by phagocytosis or antibody-dependent cell cytotoxicity. Antibodies can cross the placenta to provide passive immunity to an unborn infant . An antigen is any substance (usually a protein) that causes your immune system to produce antibodies against it. Antigens include things like bacteria, viruses, pollen and even molecules which might not normally be foreign but which the immune system has been trained to recognise as hostile because almost all cells (and therefore antigens) in the body are 'self'.

Antibodies are produced by the immune system to bind to antigens, marking them out for destruction. Antigens can also be proteins found naturally in your body cells that your immune system has learnt to attack because it mistakenly believes they're harmful invaders. Antigen therapy is a treatment where the patient is injected with antigen molecules which trigger their own immune systems into producing antibodies against whatever disease or virus they're infected with. This allows people who would ordinarily be too poorly to receive treatment (for example cancer patients) to receive vital medical intervention. Antigen-presenting cells engulf pathogens and display fragments of them on their cell surfaces bound to major histocompatibility complex (MHC) molecules, which are necessary to activate T-lymphocytes. Antigen-presenting cells include dendritic cells in the skin or mucosa, but also B lymphocytes and macrophages in the blood. Antigens are usually peptides bound to HLA molecules on APCs, which are recognized by CD4+T helper lymphocytes . Antigen presentation is an essential step for activating naive T cells during primary immune response.

The immune system uses a variety of methods to protect the body from potentially harmful antigens such as viruses and bacteria. The first line of defence is mechanical, mainly consisting of skin and mucous membranes that act as a physical barrier between foreign material and the internal tissues of the body. Antibodies bind to antigens found outside of the body, which often leads to their destruction.

Antibodies are produced by white blood cells known as B-cells. Antigen therapy is a treatment where the patient is injected with antigen molecules which trigger their own immune systems into producing antibodies against whatever disease or virus they're infected with. This allows people who would ordinarily be too poorly to receive treatment (for example cancer patients) to receive vital medical intervention. Antigen-presenting cells engulf pathogens and display fragments of them on their cell surfaces bound to major histocompatibility complex (MHC) molecules, which are necessary to activate T-lymphocytes. Antigen-presenting cells include dendritic cells in the skin mucosa, but also B lymphocytes and macrophages in the blood. Antigens are usually peptides bound to HLA molecules on APCs, which are recognized by CD4+T helper lymphocytes. Antigen presentation is an essential step for activating naive T cells during primary immune response.

Antigens function as threats whereas Antibodies function as soldiers. The antibody's job is to attack and finish off foreign invaders such as bacteria and viruses. Antigens are substances that stimulates the immune system to produce antibodies against it. Antigens include things like bacteria, viruses, pollen and even molecules which might not normally be foreign but which the immune system has been trained to recognise as hostile because almost all cells (and therefore antigens) in the body are 'self'. Antibodies are produced by white blood cells known as B-cells. Antigen therapy is a treatment where the patient is injected with antigen molecules which trigger their own immune systems into producing antibodies against whatever disease or virus they're infected with. This allows people who would ordinarily be too poorly to receive treatment (for example cancer patients) to receive vital medical intervention.