Immune System: Mechanisms of Specific Immune Response

Posted on Aug 6, 2024 in Biology

Mechanisms of Specific Immune Response

Types of Leukocytes

  • Basophils: Involved in allergic reactions, release heparin in tissues
  • Lymphocytes: Responsible for specific immune response
  • Monocytes: Phagocytose bacteria, dead cells, and organic matter; become macrophages in tissues

Types of Specific Immunity

  • Antibody-Mediated Immunity (Humoral Response): Involves the production of antibodies by B lymphocytes
  • Cell-Mediated Immunity (Cellular Response): Involves the activity of T lymphocytes and macrophages

Lymphocytes and Maturation

Lymphocytes originate from stem cells in bone marrow and mature in primary lymphoid organs:

  • Thymus: Produces T-lymphocytes
  • Bone Marrow: Produces B cells

After maturation, lymphocytes travel through blood and lymph to secondary lymphoid organs.

Antigens and Antibodies

Antigens: Foreign molecules that trigger an immune response

Antibodies (Immunoglobulins): Proteins produced by B lymphocytes in response to specific antigens

  • Variable Region: Binds specifically to antigens
  • Constant Region: Activates phagocytes and complement system

Important Immunoglobulins in Humans

  • IgA: Abundant in mucus and bodily secretions
  • IgE: Mediators in allergic reactions
  • IgM: First synthesized in response to antigens, effective against bacteria
  • IgG: Most abundant, substitutes for IgM in immune response

Antigen-Antibody Reactions

Antibodies bind to antigens on pathogens, triggering defensive reactions:

  • Agglutination of antigen-antibody complexes
  • Blocking pathogen activity
  • Stimulation of phagocytes
  • Activation of complement system (IgG and IgM antibodies)

Humoral Response

Involves the synthesis of antibodies by B lymphocytes:

  • Plasma Cells: Mature B cells that produce and secrete antibodies
  • Memory Cells: Remain in circulation and produce small amounts of antibodies after infection

Complement System

Consists of 18 proteins that assist antibodies in fighting infection:

  • Binds to pathogens
  • Leads to uptake by macrophages
  • Destroys pathogens directly

Cellular Response

Involves the activity of T lymphocytes and macrophages:

  • Macrophages: Engulf and digest antigens, present fragments on MHC proteins
  • T Cells: Recognize MHC-antigen complexes

Types of T Cells

  • CD8 T Cells (Killer Cells): Secrete cytotoxins or cytokines
  • CD4 T Cells (Helper Cells): Release lymphokines, promote proliferation of other immune cells