Immunosero

• Immunology


  Study of a host's reactions when foreign substances are introduced into the body
• Antigens


  Foreign substances that induce a host response
• Immunity


  Condition of being resistant to infection
• Chinese inhaled powder made from smallpox scabs to produce protection against the disease


  1500s
• Edward Jenner successfully prevented infection with smallpox by injecting cowpox


  Late 1700s
• Attenuation


  Making a pathogen less virulent through heat, aging, or chemical means
• Elie Metchnikoff observed phagocytosis, a natural host defense


  Late 1800s
• Emil von Behring demonstrated diphtheria and tetanus toxins could be neutralized by blood of exposed animals, leading to the theory of humoral immunity


  1903
• Louis Pasteur observed that older bacterial cultures would not cause disease in chickens, leading to the discovery of the first attenuated vaccine


  1800s
• Branches of Immunity


  • Innate or natural immunity
  • Adaptive immunity
• Innate or natural immunity


  Individual's ability to resist infection by means of normally present body functions, considered nonadaptive or nonspecific
• Adaptive immunity


  Type of resistance that is characterized by specificity for each individual pathogen and the ability to remember a prior exposure
• Leukocytes (white blood cells)


  • Play a key role in both innate and adaptive immunity
• Neutrophils


  Polymorphonuclear neutrophilic leukocytes that represent 50-75% of peripheral white blood cells, attracted to specific areas by chemotactic factors
• Eosinophils


  1. 3% of circulating white blood cells, increase in allergic reactions or parasitic infections, regulate immune response
• Basophils


  Least numerous white blood cells, function in inducing and maintaining allergic reactions
• Monocytes


  Largest cells in peripheral blood, migrate to tissues and become macrophages
• Macrophages


  Arise from monocytes, play an important role in initiating and regulating both innate and adaptive immune responses
• Dendritic cells


  Covered in long membranous extensions, most effective antigen-presenting cells and most potent phagocytic cells
• Lymphocytes


  Only white blood cells in the adaptive immune system, arise from hematopoietic stem cells and differentiate in primary lymphoid organs
• T cells


  Differentiate in the thymus, conduct cell-mediated immunity, produce cytokines that contribute to immunity
• B cells


  Derived from a lymphoid precursor, remain in the bone marrow environment, recognized by membrane-bound antibodies
• Natural killer (NK) cells

  Small percentage of lymphocytes that do not express T or B cell markers, able to kill target cells without prior exposure
• Clusters of differentiation (CD) are used to relate research findings on cell surface markers
• Regulatory T cells


  Identified by the presence of the CD3 marker on their cell surface, and either CD4, or CD8
• CD4 receptor


  Either helper or regulatory cells
• CD8-positive (CD8+) population


  Cytotoxic T cells
• CD4+ to CD8+ cells - approximately 2:1 in peripheral blood
• Natural Killer (NK) Cells

  This small percentage of lymphocytes do not express the markers of either T cells or B cells<|>Have the ability to kill target cells without prior exposure to them<|>Do not require the thymus for development but appear to mature in the bone marrow itself<|>No surface markers that are unique to NK cells, but they express a specific combination of antigens that can be used for identification
• CD16


  Receptor for the nonspecific end of antibodies
• CD56


  Because of the presence of CD16, NK cells are able to make contact with and then lyse any cell coated with antibodies
• NK cells are also capable of recognizing any foreign cell and represent the first line of defense against virally infected cells and tumor cells
• NK cells play an important role as a transitional cell bridging the innate and the adaptive immune response against pathogens
• Primary lymphoid organs


  Where maturation of B lymphocytes and T lymphocytes takes place
• Bone Marrow


  Considered one of the largest tissues in the body and it fills the core of all long flat bones<|>Main source of hematopoietic stem cells
• Thymus


  Small, flat, bilobed organ found in the thorax, or chest cavity, right below the thyroid gland and overlying the heart<|>Reaches a weight of 30 to 40 g by puberty and then gradually shrinks in size<|>Each lobe of the thymus is divided into smaller lobules filled with epithelial cells that play a central role in the differentiation process<|>Maturation of T cells takes place over a 3-week period as cells filter through the thymic cortex to the medulla<|>Large discriminating filter as it removes old and damaged cells and foreign antigens from the blood<|>Receives a blood volume of approximately 350 mL/minute
• Main Types of Secondary Lymphoid Organs

  • Adenoids
  • Tonsils
  • Thymus
  • Lymph nodes
  • Spleen
  • Peyer's patches
• Red pulp of the spleen

  Makes up more than one-half of the total volume and its function is to destroy old red blood cells (RBCs)<|>Blood flows from the arterioles into the red pulp and then exits by way of the splenic vein
• White pulp of the spleen

  Approximately 20% of the total weight of the spleen and contains the lymphoid tissue, which is arranged around arterioles in a periarteriolar lymphoid sheath (PALS)
• Lymphocytes in secondary lymphoid organs travel through the tissue and return to the bloodstream by way of the thoracic duct, which is the largest lymphatic vessel in the body and collects most of the body's lymph fluid and empties it into the left subclavian vein