Immunology Fundamentals: Reactions, Immunity Types, and Antibodies

Allergic Reactions and Hypersensitivity

An allergic reaction occurs when the Immune System (IS) triggers an inappropriate immune response that causes damage to the body's own tissues. This is the development of hypersensitivity within the body.

In cases of rapidly developing hypersensitivity, the reaction occurs between 10 and 20 minutes after exposure to an antigen, which is then specifically called an allergen.

Types of Immunity

Immunity can be broadly categorized based on how it is acquired:

Natural Immunity

Acquired by biological means or inherited from the mother. Examples include:

• Enzymes in tears and skin oils.
• Mucus that traps bacteria and small particles.

Active Immunity

The body produces antibodies in response to the presence of an antigen. This type of immunity is durable and can often last a lifetime.

Passive Immunity

Provided by the mother through the placenta or breast milk to the fetus or newborn. It lasts only a few weeks or months, corresponding to the lifespan of the transferred antibodies. Example: Mother's colostrum.

Artificial Immunity

Immunity acquired through therapy or medical treatment.

Active Artificial Immunity (Vaccines)

It stimulates the body to produce specific antibodies against pathogens that are provided in an attenuated (weakened) form. This serves as a preventive measure. Example: Vaccines.

Passive Artificial Immunity (Fluid Therapy)

Acquired through fluid therapy, which consists of supplying serum from immune donors. It serves as a support if the active immune response is insufficient. Its duration is limited.

Understanding Autoimmune Diseases

Autoimmune diseases occur when the immune system (IS) attacks the body's own cells and tissues instead of protecting them. The IS becomes the aggressor, leading to an exaggerated immune response against substances and tissues normally present in the body.

The causes are related to protein recognition issues between the cell membrane surfaces of the IS and the body's own cells.

Systemic Autoimmune Diseases

Antibodies attack antigens that are not specific to a particular organ. Example: Lupus erythematosus.

Local Autoimmune Diseases

Diseases primarily affecting specific areas, often categorized as endocrine, dermatological, or hematological.

Blood Transfusion Process

Blood transfusion is the transfer of whole blood or a specific blood component from one person (the donor) to another (the recipient).

Chemical Structure of Antibodies (Immunoglobulins)

Antibodies are globular proteins composed of four polypeptide chains attached by disulfide bridges.

The two largest chains are called heavy chains, and the two smaller chains are called light chains.

At one end of these chains are the variable regions (whose amino acid sequence differs for each specific antigen, Ag). The remaining regions are constant regions.