immune system

Examples of immune system in the following topics:

• Immunodeficiency

  • Immunodeficiency occurs when the immune system cannot appropriately respond to infections.
  • Neutropenia is one form in which the immune system produces a below-average number of neutrophils, the body's most abundant phagocytes.
  • As the illness progresses, it interferes more and more with the immune system.
  • This weakens the immune system, allowing opportunistic infections.
  • During the chronic phase, the consequences of generalized immune activation coupled with the gradual loss of the ability of the immune system to generate new T cells appear to account for the slow decline in CD4+ T cell numbers.

• Innate Immune Response

  • The immune system serves to defend against pathogens: microorganisms that attempt to invade and cause disease in a host.
  • Mammalian immune systems evolved for protection from such pathogens.
  • Central to this goal, the immune system must be capable of recognizing "self" from "other" so that when it destroys cells, it destroys pathogen cells and not host cells.
  • Components of both immune systems constantly search the body for signs of pathogens.
  • Features of the immune system (e.g., pathogen identification, specific response, amplification, retreat, and remembrance) are essential for survival against pathogens.

• Regulating Immune Tolerance

  • The innate and adaptive immune responses discussed thus far comprise the systemic immune system (affecting the whole body), which is distinct from the mucosal immune system.
  • Mucosal immunity is formed by mucosa-associated lymphoid tissue, or MALT, which functions independently of the systemic immune system; it has its own innate and adaptive components.
  • The systemic and mucosal immune systems use many of the same cell types.
  • APCs of the mucosal immune system are primarily dendritic cells, with B cells and macrophages playing minor roles.
  • This allows the immune system to detect and deal with pathogens very quickly after they enter the body through various mucous membranes.

• Pathogen Recognition

  • These PAMPs allow the immune system to recognize "self" from "other" so as not to destroy the host.
  • The immune system has specific cells with receptors that recognize these PAMPs .
  • The immune system has specific cells whose job is to recognize pathogen-associated molecular patterns.
  • The characteristics and location of cells involved in the innate immune system are described in this chart.
  • Leukocytes (1, 2, 3) are white blood cells that play an important role in the body's immune system.

• The Complement System

  • The innate immune system serves as a first responder to pathogenic threats that bypass natural physical and chemical barriers of the body.
  • Using a combination of cellular and molecular attacks, the innate immune system identifies the nature of a pathogen and responds with inflammation, phagocytosis (where a cell engulfs a foreign particle), cytokine release, destruction by NK cells, and/or a complement system.
  • In this concept, we will discuss the complement system.
  • The complement system is so named because it is complementary to the antibody response of the adaptive immune system.
  • When innate mechanisms are insufficient to clear an infection, the adaptive immune response is informed and mobilized.

• Physical and Chemical Barriers

  • The immune system comprises both innate and adaptive immune responses.
  • From an historical perspective, the innate immune system developed early in animal evolution, roughly a billion years ago, as an essential response to infection.
  • The skin is considered the first defense of the innate immune system; it is the first of the nonspecific barrier defenses.
  • The blood-brain barrier also protects the nervous system from pathogens that have already entered the blood stream, but would do significantly more damage if they entered the central nervous system.
  • In the innate immune system, they serve to move pathogens out of the respiratory system via a concerted sweeping motion.

• Cytotoxic T Lymphocytes and Mucosal Surfaces

  • The lymphatic system houses large populations of immune cells which are released upon detection of a pathogen.
  • Although the immune system is characterized by circulating cells throughout the body, the regulation, maturation, and intercommunication of immune factors occur at specific sites that are known as lymph nodes.
  • Cells of the immune system can travel between the distinct lymphatic and blood circulatory systems, which are separated by interstitial space, by a process called extravasation (passing through to surrounding tissue).
  • Recall that cells of the immune system originate from stem cells in the bone marrow.
  • Describe the features of the lymphatic system as they relate to the immune response

• Immunological Memory

  • Immunological memory allows the adaptive immune system to very rapidly clear infections that it has encountered before.
  • The adaptive immune system has a memory component that allows for a rapid and large response upon re-invasion of the same pathogen.
  • This is known as the secondary immune response.
  • The result is a more rapid production of immune defenses.
  • The immune response to vaccination may not be perceived by the host as illness, but still confers immune memory.

• Antigen-presenting Cells: B and T cells

  • An antigen is a molecule that binds to a specific antibody, often stimulating a response in the immune system as a result.
  • The adaptive immune response activates when the innate immune response insufficiently controls an infection.
  • In fact, without information from the innate immune system, the adaptive response could not be mobilized.
  • The two types of lymphocytes of the adaptive immune response are B and T cells .
  • Explain the role played by B and T cells in the adaptive immune system

• Humoral Immune Response

  • It is the immense number of B cells in the body, each of which produces a unique antibody, that allows the immune system to detect such a wide variety of pathogenic antigens.
  • B cells containing antibodies that recognize "self" antigens are destroyed before they can mature, preventing the immune system from attacking the host.
  • Antibodies are the agents of humoral immunity.
  • These antibodies circulate in the blood stream and lymphatic system, binding with the antigen whenever it is encountered.
  • This describes the host's active response of the immune system to an infection or to a vaccination.