Immune System Fundamentals: Key Concepts

Antibody: Structure and Function

Molecules manufactured by B lymphocytes in response to contact with an antigen. Chemically, they are globular plasma proteins that detect and specifically bind to the antigen, leading to the humoral immune response. This allows them to detect and neutralize or bind to microorganisms that are then phagocytosed by macrophages.

Antigen: Immune System Trigger

A molecule capable of triggering an immune response. These molecules are foreign; the immune system does not recognize them as its own. They are detected by antibodies. Antigens are macromolecules of protein or polysaccharide nature.

Autoimmunity: Immune System Error

This occurs when the immune system synthesizes antibodies against the organism itself. It is an immune system error because it cannot recognize specific molecules as its own. Examples include Multiple Sclerosis and Psoriasis.

Immunodeficiency: Impaired Immune Function

The inability of the immune system to control microbial infections. Its causes include genetic diseases, errors in the development of lymphoid organs, or viral infections. The immune system has a much lower activity than normal.

Immunity: Disease Resistance

The resistance that individuals possess against the actions or pathogenic substances of foreign microorganisms.

Interferon: Antiviral Protein

A protein with antiviral activity produced by animal cells in response to viral infection. Interferons are synthesized as a rapid response, quicker than antibody formation, to viral infection. They are widely used as therapeutic agents against viral diseases and some forms of cancer.

Humoral Immunity

Cellular Immunity

Lymphocyte: Key Immune Cell

Lymphocytes are leukocytes present in the blood, lymph, and lymphoid organs. They do not emit pseudopodia and therefore do not have the capacity to phagocytose. They form in the primary lymphoid organs from unipotential progenitor cells, from where they migrate to secondary lymphoid organs.

B Lymphocyte

T Lymphocyte

Macrophage: Phagocytic Immune Cell

Macrophages are monocytes, which are white blood cells that migrate from the bloodstream and small vessels into the tissue. They participate in three phases of the immune response: antigen recognition, lymphocyte activation, and elimination of the antigen by phagocytosis.

Primary Immune Response

Occurs with the first contact with an antigen. There is a latency phase, and then comes the growth phase that gives rise to antibodies in the individual's blood.

Secondary Immune Response

Occurs with a new contact with the same antigen that previously triggered a primary immune response. This second response is more rapid and significant in terms of the appearance and quantity of antibodies.

Vaccine: Active Immunization

Vaccines produce active immunization by inoculating attenuated antigens that induce a primary immune response. This generates immunological memory against the antigen, which provides permanent immunity.

Serum Therapy: Passive Immunization

A type of passive immunization by injection of antigen-specific antibodies that target the disease-causing agent. The body is not involved in developing these antibodies. Its effect is immediate and lasts a few months while the antibodies are present in the plasma. No immunological memory is generated.