5.1 immunoglobulin

• Adaptive immunity is an immunity that occurs after exposure to an antigen from a pathogen or a vaccination
• Adaptive immunity is activated when the innate immune response is insufficient to control an infection
• The adaptive immune response takes days or even weeks to become established, much longer than the innate response
• The adaptive immune response is more specific to pathogens and has memory
• The adaptive immune response involves two types of responses: the humoral immune response controlled by activated B cells and the cell-mediated immune response carried out by T cells
• The humoral-mediated immune system, also known as antibody-mediated immunity, deals with antigens from pathogens that are freely circulating or outside infected cells
• In the humoral immune response pathway, antigens enter the body, bind to B cells, and helper T cells assist in B cell proliferation
• Plasma cells carry antibodies that are antigen-specific and have specific binding receptors of the activated B cells in the humoral immune response pathway
• The cell-mediated immune response does not involve antibodies and is directed primarily at microbes that survive in phagocytes and infect non-phagocytic cells
• Cellular immunity involves T lymphocytes and defense against intracellular microbes by activation of macrophages, natural killer cells, and production of antigen-specific cytotoxic T-lymphocytes
• CD8 T cells' primary function is to kill cells infected with viruses or other intracellular pathogens, while CD4 T cells help other immune system cells respond to extracellular pathogens
• Cellular immunity protects the body by activating antigen-specific cytotoxic T-cells, macrophages, and NK cells, and stimulating cells to secrete cytokines that influence the function of other cells involved in immune responses
• Humoral immunity is responsible for destroying pathogens by producing antibodies against them, while cell-mediated immunity destroys pathogens that have invaded cells without the presence of antibodies
• Humoral immunity works against extracellular pathogens, while cell-mediated immunity works against intracellular pathogens
• Humoral immunity is rapid in response, while cell-mediated immunity shows a delay but provides a permanent action against pathogens
• Immunological memory in T-lymphocytes causes numerous circulating T8-memory cells and T4-memory cells to develop, persisting for the remainder of a person's life
• Helper T cells induce immune responses, while cytotoxic T cells destroy virus-infected and tumor cells directly
• Attachment is a strong reciprocal emotional bond between an infant and a primary caregiver

  
• Antibody Titer: The amount of antibody in the serum

  
• Pattern of Antibody Levels During Infection:

  • Primary Response:
  • After initial exposure to antigen, no antibodies are found in serum for several days
  • A gradual increase in titer, first of IgM and then of IgG is observed
  • Most B cells become plasma cells, but some become long living memory cells
  • Gradual decline of antibodies follows
• Secondary Response:

  • Subsequent exposure to the same antigen gives a faster and greater antibody response
  • Increased antibody response is due to the existence of memory cells, which rapidly produce plasma cells upon antigen stimulation
• Repeat infections by the same virus are met immediately with a strong and specific response that usually effectively stops the infection with less reliance on the innate system
• Immune to infection with a virus: immune memory

  • Vaccines protect against infection because of immune memory
• Natural Immunity:

  • Active: when a vaccine triggers the immune system to produce antibodies against the disease as though the body had been infected with it
  • This teaches the body's immune system how to produce the appropriate antibodies quickly
  • Two ways of natural resistance against invading microbes: natural active and natural passive/artificial
• Passive Immunity:

  • Borrowed from another source and lasts for a short time
  • Translocation of active humoral immunity from one individual to another in the form of custom-made antibodies
  • Two ways of passive resistance against invading microbes: passive natural and passive artificial
• Natural Passive Immunity:

  • Occurs during pregnancy when antibodies are passed from the maternal blood into the fetal bloodstream
  • Transferred through the placenta in the form of antibodies, mainly IgG and IgA
• Natural Passive Immunity cont...

  • Provides some protection for the child for a short time after birth, transferred through breast milk
  • Human milk contains oligosaccharides, mucins, lactoferrin, B12 binding protein, bifidus factor, fibronectin, gamma-interferon, hormones, and growth factors that enhance the baby's immune system
• Adaptive Immunity:

  • Second line of defense system
  • Specific response with a slow response time to pathogens (7-10 days)
  • Memory function to prevent re-infection
• Adaptive immunity serves as the secondary line of host defense, activated when the innate immune response is insufficient to control an infection

  • T-cells kill pathogens directly, B-cells secrete antibodies, essential for long-term immunity
• Each chain has two domains - one variable (V) domain and one constant (C) domain.