Immunity (medicine)

The biological defense mechanisms of an organism

Immunity in medicine refers to the balanced state of having adequate biological defenses to fight infection, disease, or other unwanted biological invasion, while having adequate tolerance to avoid allergy and autoimmune disease.

Overview

Diagram of the immune system

The immune system is a complex network of cells, tissues, and organs that work together to defend the body against harmful invaders. It can be broadly divided into two categories: innate immunity and adaptive immunity.

Innate Immunity

Innate immunity is the first line of defense and is present from birth. It includes physical barriers such as the skin and mucous membranes, as well as immune cells like phagocytes and natural killer cells. These components act quickly to prevent the spread of infections.

Components of Innate Immunity

• Physical Barriers: The skin and mucous membranes act as physical barriers to pathogens.
• Cellular Defenses: Phagocytes, such as macrophages and neutrophils, engulf and destroy pathogens.
• Chemical Defenses: Lysozyme in saliva and stomach acid are examples of chemical defenses.

Adaptive Immunity

Diagram of the adaptive immune response

Adaptive immunity is more complex and involves the activation of lymphocytes, which are specialized white blood cells. This type of immunity is specific to particular pathogens and has a memory component, allowing for a faster response upon re-exposure to the same pathogen.

Components of Adaptive Immunity

• Humoral Immunity: Mediated by B cells and the production of antibodies.
• Cell-mediated Immunity: Involves T cells that destroy infected cells and coordinate the immune response.

Development of Immunity

Louis Pasteur, a pioneer in the study of immunity

Immunity can be acquired naturally or artificially. Natural immunity occurs through exposure to pathogens, while artificial immunity is acquired through vaccination.

Natural Immunity

Natural immunity can be active or passive. Active natural immunity results from direct exposure to a pathogen, while passive natural immunity is acquired through maternal antibodies.

Artificial Immunity

Artificial immunity is also divided into active and passive forms. Active artificial immunity is achieved through vaccination, while passive artificial immunity involves the administration of antibodies, such as in the case of antitoxins.

Historical Perspectives

Administration of diphtheria antitoxin

The concept of immunity has evolved over centuries. Early observations of immunity were made by Edward Jenner with the development of the smallpox vaccine. Later, Louis Pasteur expanded on these ideas, leading to the development of vaccines for diseases such as rabies.

Immune System Disorders

The immune system can malfunction, leading to disorders such as autoimmune diseases, immunodeficiency, and allergies.

Autoimmune Diseases

In autoimmune diseases, the immune system mistakenly attacks the body's own cells. Examples include rheumatoid arthritis and type 1 diabetes.

Immunodeficiency

Immunodeficiency occurs when the immune system is not functioning properly, making individuals more susceptible to infections. This can be congenital or acquired, as in the case of HIV/AIDS.

Allergies

Allergies are hypersensitive immune responses to harmless substances such as pollen or food.

Related Pages

• Immune system
• Vaccination
• Autoimmune disease
• Allergy
• Immunodeficiency