1.1 EL SISTEMA INMUNITARIO. INTRODUCCIÓN Y CONCEPTOS BÁSICOS

Introduction to the Immune System

Understanding Immunity and Its Origins

• The term "immunity" originates from the Latin word "immunitas," which referred to exemption from taxes in ancient Rome, highlighting a historical context of protection.

• In medieval times, the concept evolved to describe individuals who survived infections, but even Edward Jenner, a pioneer of vaccination, did not use the term "immunology."

• Louis Pasteur later redefined immunity in 1884 with roots in "in" (from within) and "munera" (to defend), emphasizing internal defense mechanisms.

The Immune System's Functionality

• The immune system distinguishes between self (the body’s own cells) and non-self (foreign invaders), crucial for preventing autoimmunity.

• Education of immune cells occurs primarily in the thymus and bone marrow, teaching them to recognize what is 'self' to avoid self-harm.

Mechanisms of Immune Response

• Positive and negative selection processes are essential for training immune cells to prevent autologous damage while preparing for diverse pathogens.

• The immune system can potentially respond to over 100 billion different threats through preformed clones that activate upon infection.

Types of Threats Recognized by the Immune System

Diverse Pathogens

• The immune system has evolved mechanisms to combat various pathogens including viruses, bacteria, fungi, protozoa, and larger parasites like worms.

Size Matters: Intracellular vs. Extracellular Pathogens

• Viruses are obligate intracellular pathogens requiring host cell machinery for replication; they are very small compared to other organisms.

• In contrast, large parasites such as intestinal worms cannot be engulfed by immune cells and are classified as extracellular threats.

Additional Threat Categories

• Tumors arise when environmental factors alter cellular structures; these modified proteins can trigger an immune response as foreign entities.

Understanding Immunity and Its Mechanisms

The Role of the Mother’s Immune System

• The mother carries an embryo for nine months, which contains proteins from the biological father, leading to a different genetic makeup.

• Despite potential immune reactions against these paternal proteins, the mother's body does not reject the embryo due to effective reproductive regulation at the placental level.

• This regulation prevents the immune system from attacking the embryo under normal circumstances.

• Approximately 5% of spontaneous abortions are attributed to immunological causes.

Recap of Key Concepts in Immunology

• A review was conducted on the etymological origins of "immunity" and a basic definition of the immune system was provided.

• Discussions included reflections on significant characteristics of the immune system and its various types.

Threats to Individuality and Pathogen Size

• The size of pathogens is crucial for how they are perceived by the immune system; understanding this helps in recognizing threats to individuality.