Immunology Chapter: Acquired Immunity

Acquired Immunity

• Also known as adaptive or specific immunity
• Defends the host from infection in a particular way
• Different from innate immunity, which is present from birth
• Acquired after exposure to an antigen
  • Either through infection or vaccination (active immunity)
  • Or by receiving antibodies or lymphocytes from another source (passive immunity)
• Adaptive immunity has four key characteristics:

Antigenic Specificity

• The immune system protects individuals from harm
  • Caused by foreign pathogens or pre-cancerous cells
• The system must distinguish self from non-self to avoid harming the body
• It can differentiate between billions of different antigens
• Antibodies are crucial in distinguishing minute differences in protein structures

Diversity

• Immune responses are specialized and designed to combat various types of microbes

Immunological Memory

• Once the immune system encounters an antigen, it develops a “memory”
• Subsequent exposure to the same antigen triggers a stronger and faster response (secondary response)
  • Unlike the initial response (primary response)
• This memory helps provide long-lasting immunity to many infections

Immunologic Memory

• Leads to faster and more intense secondary immune response
• Memory lymphocytes, long-lived cells formed during the primary response, are crucial for this response
• Optimizes the ability to fight recurrent infections
• Ensures a faster and improved response to later encounters with the same antigen

Vaccines

• Memory is a core function of vaccines
• Providing long-lasting protection against infections

Self/Non-Self Recognition

• The immune system mainly targets foreign antigens
• This indicates a capability for self/non-self recognition
• It helps distinguish between the body's own cells (self) and foreign substances (non-self)

Types of Acquired Immunity

• Active Immunity:
  • Develops after exposure to an antigen
  • Takes time and is long-lasting
  • Creates an immunological memory
• Passive Immunity:
  • Results from receiving pre-formed antibodies
  • Acts immediately but is temporary
  • Does not create immunological memory

Active Immunity Subtypes

• Natural Active Immunity: Exposure to a disease agent triggers the body's immune response
• Artificial Active Immunity: Immunization with a vaccine stimulates the production of antibodies

Passive Immunity Subtypes

• Natural Passive Immunity: Antibodies move from mother to baby (e.g., through breast milk), providing temporary protection
• Artificial Passive Immunity: Receiving antibodies from an external source (e.g., antiserum) offers short-term protection

Herd Immunity

• A type of indirect protection from infectious diseases
• Occurs when a substantial portion of a population is immune, limiting the spread of infection among susceptible individuals

Humoral Immunity

• Involves antibodies produced by B lymphocytes
• Used to combat pathogens
• Antibody production occurs after antigen recognition by B-cells

Cell-Mediated Immunity

• Involves T-cells, other immune cells (NK), and phagocytes
• A crucial defense mechanism against diverse pathogens
• Functions include targeting infections, cancers and participating in transplant rejection

This quiz covers the fundamental concepts of acquired immunity, focusing on its characteristics such as antigenic specificity, diversity, and immunological memory. Understand the differences between active and passive immunity, and how the immune system recognizes and responds to pathogens. Test your knowledge about how the body develops immunity after exposure to antigens.