lymphatic system

• The lymphatic system helps maintain fluid balance in the body by collecting excess fluid and returning it to the bloodstream.
• Activated T cells do not respond to antigens in solution
• Adaptive immunity


  Includes cell-mediated and antibody-mediated immunity
• Antibody-mediated immunity

  • Provided by B cells
  • Defends against antigens and pathogens in body fluids
  • Also known as humoral immunity
• David, known as the boy in the bubble, was born with severe combined immunodeficiency (SCID), a genetic disorder that virtually wipes out the body's immune system
• David was placed in a sterile plastic bubble immediately after birth to protect him from infections
• David's environment, including toys, food, and clothing, had to be sterilized before being given to him
• David's story of living in a bubble due to SCID spread across the world, and he became known as the boy in the bubble
• Cell-mediated immunity


  • Provided by cytotoxic T cells
  • Defends against abnormal cells and pathogens inside the body cells
• Both cell-mediated and antibody-mediated immunity are important and function under different circumstances
• Antibodies produced by activated B cells cannot cross the plasma membrane and do not perform the function of cell-mediated immunity
• David's only physical contact with others was through a barrier of rubber gloves built into the bubble's wall
• The only treatment available for SCID at the time was a bone marrow transplant, which was not successful in David's case
• SCID is a genetic disorder that affects male children and can be fatal due to the weakened immune system
• Artificially acquired active immunity involves stimulating the body to produce antibodies, often through vaccination to prevent disease
• Adaptive immunity can be categorized as active or passive, further divided into naturally acquired or artificially induced
• David learned about the danger of germs at a young age due to his medical condition
• In 1983, David underwent a bone marrow transplant from his sister Catherine, which initially seemed successful but later led to his deterioration and death
• Artificially acquired passive immunity involves receiving antibodies to fight infection or prevent disease, such as in the case of rabies virus exposure
• Passive immunity occurs when antibodies are transferred from another source, either naturally or artificially
• A vaccine is designed to induce an immune response using dead or inactive pathogens or antigens derived from them
• David lived in a sterile chamber at the Texas Children's Hospital before a second chamber was built at his parents' house
• Naturally acquired active immunity develops after birth as we encounter new pathogens or antigens, similar to learning a new language
• In 1977, NASA scientists built a miniaturized space suit for David to leave his bubble, although he found the experience frightening
• David's death revealed that the cause was cancer from an undetected virus in Catherine's marrow, leading to a breakthrough in medical science
• Naturally acquired passive immunity happens when a baby receives antibodies from the mother, either through the placenta or breast milk
• Artificially induced passive immunity


  Transfer of antibodies from processed plasma with high quantities of antibodies for a specific virus into a host to help fight infection or disease
• Specificity in immune response


  • A specific defense is activated by a specific antigen, resulting in the immune response targeting that particular antigen only
• Memory in immune response


  • Memory cells enable the immune system to remember an antigen it has previously encountered, leading to a faster, stronger, and longer-lasting attack upon re-exposure to the antigen
• Active immunity


  Transfer of antigen to stimulate the immune response, leading to the person producing antibodies against that antigen
• Both categories of adaptive immunity and their subtypes have four common properties
• Tolerance in immune response

  • The immune system does not respond to all antigens, exhibiting tolerance towards self-antigens and attacking only foreign antigens or non-self antigens
• Versatility in immune response

  • The immune system must be ready to confront any antigen at any time, resulting from the large diversity of lymphocytes and variability in the structure of antibodies
• Reduction in helper T cell population is largely responsible for the immune deficiency observed in acquired immunodeficiency virus (AIDS)
• Cytotoxic T cells


  Involved in the direct attack of damaged or infected cells by physically and chemically attacking antigens
• Memory T cells


  Respond to antigens they have encountered before, attacking familiar antigens through cloning
• Activated B cells differentiate into cells that produce antibodies which bind to and attack antigens in the bloodstream
• Other types of regulatory T cells

  • Inflammatory T cells
  • Suppressor or inducer T cells
• T cells differentiate into specific cell types under suitable conditions to attack antigens and enhance the immune response
• Activation of T cells generally occurs after phagocytes present the antigen on their surface