immunosero

• Antigens


  Substances that are able to combine to an antibody or sensitized T-cells
• Immunogens


  Substances that cause immune response (e.g. release of antibodies)
• All immunogens are antigens; but not all antigens are immunogens
• Factors Influencing The Immune Response

  • Age
  • Overall Health
  • Dose
  • Route of Inoculation
  • Genetic Capacity
• Elderly


  • Decreased response to antigenic stimulation
• Neonates


  • Their immune system is not completely developed
• Malnutrition, fatigue or stress


  • Likely to mount a successful immune response
• Larger the amount of an immunogen one is exposed to

  • The greater the immune response
• Routes of Inoculation


  • Intravenous
  • Intradermal
  • Subcutaneous
  • Oral contact
• Intravenous


  • Fastest route to induce an immune response
• Intradermal, Subcutaneous


  • Local lymph nodes react with the immunogen
• Major Histocompatibility Complex (MHC)


  System of genes that code for cell surface molecules that play an important role in antigen recognition
• Traits of Immunogens


  • Macromolecular size
  • Foreignness
  • Chemical Structure and Molecular complexity
• Macromolecular size


  • Most substances greater than 10,000 D induce immune response (there are exceptions)
• Foreignness


  • An antigen derived from a taxonomically distant object elicit a better immune response than antigens derived from a nearer taxa or the same taxa
• Chemical Structure and Molecular complexity


  • An antigen with a more complex structure would have the ability to elicit immune response better than those with a simpler structure
• Proteins and polysaccharides are the best immunogens because their chemical composition is more complex
• Ability to be processed and presented by APCs

  • They must be easily phagocytized, degraded, and presented by MHC molecules to T cells
• Epitopes


  Antigenic determinants, the key portion of the immunogen that is recognized in the immune response
• Epitopes


  • Can be Linear (sequential) or Conformational
• Haptens


  Small organic molecules that are antigenic but non-immunogenic, can be complexed to larger molecules to stimulate a response
• Adjuvants


  Substances administered with an immunogen that increases the immune response
• Autoantigens


  Antigens that belong to the host, do not evoke an immune response under normal circumstances
• Alloantigens


  From other members of the host's species, capable of eliciting an immune response
• Heteroantigens


  From other species such as other animals, plants or microorganisms
• Heterophile Antigens


  Heteroantigens that exist in unrelated plants or animals, either identical or closely related in structure so that antibody to one will cross-react with antigen of the other
• Human Leukocyte Antigens (HLA)


  MHC molecules which function to bring antigen to the cell surface for recognition by T cells
• MHC


  • Encoded by a system of genes arrayed within a long continuous stretch of DNA on chromosome 6 in humans and on chromosome 17 in mice
• MHC Molecule Classes


  • Class I
  • Class II
  • Class III
• Class I Molecules


  • Coded in A, B, and C Loci, found on all nucleated cells
• Class II Molecules


  • Coded in D region, found on Antigen Presenting Cells (B cells, Macrophages, Dendritic cells, monocytes)
• Class III Molecules


  • Coded in C4a, C4b and C2 regions, plasma proteins
• The MHC system is described as polymorphic, because there are so many possible alleles at each location
• Uses of MHC

  • Disease correlation
  • Tissue compatibility
  • Paternity testing
• Class I Pathway


  Class I molecules function to present endogenous peptides (Viral proteins or intracellular products of tumor cells) to CD8 (Cytotoxic) cells
• Class II Pathway


  Class II molecules function to present exogenous peptides (Bacterial antigens, or anything that can be endocytosed) to CD4 (helper) cells
• Genes of the Major Histocompatibility Locus

  • Class I
  • Class II
  • Class III
  • Cytokine Genes
• Clinical Significance of MHC

  • Transplantation
  • Autoimmune disorders
  • Vaccine response and nonresponse
  • Selective immunity
• Lymphocytes


  The key cell involved in the immune response
• Lymphocytes represent between 20 and 40 percent of the circulating white blood cells