Adaptive (acquired) immunity

Examples of Adaptive (acquired) immunity in the following topics:

• Overview of the Immune System

  • Adaptive (acquired) immunity creates immunological memory after an initial response to a specific pathogen, leading to an enhanced response to subsequent encounters with that same pathogen.
  • This process of acquired immunity is the basis of vaccination.
  • Adaptive immunity is often sub-divided into two major types depending on how the immunity was introduced.
  • Naturally acquired immunity occurs through contact with a disease causing agent, when the contact was not deliberate, whereas artificially acquired immunity develops only through deliberate actions such as vaccination.
  • Both naturally and artificially acquired immunity can be further subdivided depending on whether immunity is induced in the host or passively transferred from an immune host.

• Primary and Secondary Antibody Responses

  • The immune system protects organisms from infection first with the innate immune system, then with adaptive immunity.
  • Adaptive (or acquired) immunity creates immunological memory after an initial response to a specific pathogen, leading to an enhanced response to subsequent encounters with that same pathogen.
  • This process of acquired immunity is the basis of vaccination.
  • In humans, immunodeficiency can either be the result of a genetic disease such as severe combined immunodeficiency, acquired conditions such as HIV/AIDS, or the use of immunosuppressive medication.
  • The innate system is present from birth and protects an individual from pathogens regardless of experiences, whereas adaptive immunity arises only after an infection or immunization and hence is "acquired" during life.

• Overview of Adaptive Immunity

  • The adaptive immune system works to protect and heal the body when the innate immune system fails.
  • The adaptive immune system starts to work after the innate immune system is activated.
  • The adaptive immune response occurs a few days after the innate immune response occurs.
  • Adaptive immunity is triggered when a pathogen evades the innate immune system for long enough to generate a threshold level of an antigen.
  • Active immunity is generally long-term and can be acquired by infection followed by B cells and T cells activation, or artificially acquired by vaccines, in a process called immunization.

• Adaptive Immunity and the Immunoglobulin Superfamily

  • Adaptive immunity is stimulated by exposure to infectious agents and recruits elements of the immunoglobulin superfamily.
  • Adaptive immunity is stimulated by exposure to infectious agents and increases in magnitude and defensive capabilities with each successive exposure to a particular microbe.
  • There are two types of adaptive immune responses: humoral immunity and cell-mediated immunity.
  • They are commonly associated with roles in the immune system.
  • Describe the role of immunoglobulins in the adaptive immune response, specifically in humoral immunity

• Antigen-presenting Cells: B and T cells

  • The adaptive, or acquired, immune response to an initial infection takes days or even weeks to become established, much longer than the innate response.
  • Adaptive immunity occurs after exposure to an antigen either from a pathogen or a vaccination.
  • The adaptive immune response activates when the innate immune response insufficiently controls an infection.
  • Adaptive immunity also involves a memory, which gives the host long-term protection from reinfection by the same type of pathogen; upon re-exposure, this host memory will facilitate a rapid and powerful response.
  • Explain the role played by B and T cells in the adaptive immune system

• Types of Adaptive Immunity

  • The adaptive immune response is mediated by B and T cells and creates immunity memory.
  • The adaptive immune system mounts a stronger, and antigen specific immune response after the innate immune response fails to prevent a pathogen from causing an infection.
  • There are two subdivisions of the adaptive immune system: cell-mediated immunity, and humoral immunity.
  • Cell mediated immunity is controlled by type 1 helper T-cells (Th1) and cytotoxic T-cells.
  • Antibodies to provide a number of functions in humoral immunity.

• Natural Active Immunity

  • Naturally acquired active immunity occurs when a person is exposed to a live pathogen, develops the disease, and then develops immunity.
  • There are two ways to acquire active resistance against invading microbes: active natural and active artificial.
  • Naturally acquired active immunity occurs when the person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the primary immune response.
  • In a similar manner, administration of two doses of hepatitis A vaccine generates an acquired active immune response leading to long-lasting (possibly lifelong) protection.
  • The principle behind immunization is to introduce an antigen, derived from a disease-causing organism, that stimulates the immune system to develop protective immunity against that organism, but which does not itself cause the pathogenic effects of that organism.

• WBC Function

  • Leukocyte functions may be classified as either innate or adaptive immune system, based on several characteristics.
  • Innate immune system functions from leukocytes include:
  • Compared to the innate immune system, adaptive immune functions work much faster and have a memory component to them as well, which prevents reinfection by the same pathogen, but more time typically passes before the adpative immune system is functional.
  • Adaptive immune functions of leukocytes include:
  • The T cells will then start the adaptive immune response by rapidly proliferating and differentiating.

• Passive Immunization

  • There are two types of passive immunity: artificial and natural .
  • Passive immunity can also be acquired naturally by the fetus due to the transfer of antibodies by the maternal circulation in utero through the placenta around the third month of gestation.
  • For the newborn to have lasting protection, active immunity must be received.
  • Natural immunity occurs through contact with a disease causing agent, when the contact was not deliberate, where as artificial immunity develops only through deliberate actions of exposure.
  • Passive immunity is short lived, and usually lasts only a few months, whereas protection via active immunity lasts much longer, and is sometimes life-long.

• Active and Passive Humoral Immunity

  • The humoral immune response is the aspect of immunity that is mediated by secreted antibodies.
  • There are two types of humoral immunity, active and passive humoral immunity.
  • Active humoral immunity refers to any form of immunity that occurs as a result of the formation of an adaptive immune response from the body's own immune system.
  • Maternal passive immunity is a type of naturally acquired passive immunity, and refers to antibody-mediated immunity conveyed to a fetus by its mother during pregnancy.
  • Artificially acquired passive immunity is a short-term immunization achieved by the transfer of antibodies, and can be administered in several forms: as human or animal blood (usually horse) plasma or serum, as pooled human immunoglobulin for intravenous (IVIG) or intramuscular (IG) use, and as monoclonal antibodies (MAb).