Understanding Allergies, Transplants, and Autoimmune Diseases

Allergies

An allergy is an altered and abnormal reaction of the organism to certain antigens, called allergens. Exaggerated reactions occur, which prove to be harmful upon repeated contact with the antigen; these are known as hypersensitivity or anaphylactic reactions.

Hypersensitivity reactions may occur immediately or be delayed. An animal subjected to an antigen of this type is called hypersensitive or allergic, while the antigen is known as an allergen or sensitizing agent.

Immediate Hypersensitivity Reactions

The first contact induces the formation of IgE-type immunoglobulins. Histamine and other mediators cause dilation and increased vascular permeability, resulting in edema. It also causes the contraction of smooth muscles in the bronchi. An anaphylactic reaction throughout the body can cause death by anaphylactic shock.

Allergy treatment is performed by administering antihistamines. Vaccines are inoculated subcutaneously in successively increasing amounts of antigen to protect mast cells.

Delayed Hypersensitivity Reactions

Examples include the acute rejection of tissue transplants from a donor or reactions to tuberculin skin tests and contact with certain substances. A global increase in alergopatías has been observed in recent years, largely depending on environmental factors such as stress, increased smoking, and poor diet. Chronic allergies often require daily treatment.

Transplants

A transplant is the transfer of an organ or tissue from one person to another, or from one body area to another, to replace a diseased structure or restore organ function. Frequently transplanted structures include skin, kidney, cartilage, bone, and cornea. There are several types of transplants:

• Autotransplants: Tissue is transplanted from one place to another within the same individual.
• Syngeneic: The donor and recipient are genetically identical individuals.
• Homograft: Tissue is transplanted from one individual to another of the same species.
• Heterotransplants or Xenotransplantation: The donor and recipient belong to different species.

Autoimmune Diseases

• Psoriasis: Skin wounds that spread across the body.
• Multiple Sclerosis: The immune system attacks myelin, the sheath that covers nerve fibers, leading to progressive neurological decline.