A Brief Overview of Immunology Dennis E. Lopatin, Ph.D. University of Michigan

What’s the bottom line? Immune system recognizes foreign agents Immune response is mounted to produce activated T cells and specific antibodies Antibodies react with foreign agent Activated T cells react with foreign agent Activated T cells may influence other cells Antibodies provide specificity to non-specific cytotoxic systems Immune system “remembers: what it did.

What happens upon antigen exposure? B lymphocytes T lymphocytes Virgin lymphocyte pool PRIMARY RESPONSE effector cells memory cell pool SECONDARY RESPONSE Exposure to Antigen (Naturally-acquired or artificial) effector cells memory cell pool Activated T lymphocytes Plasma cells Regulatory Cytotoxic Antibodies

Polymorphonuclear leukocytes (or Granulocytes) Where is that stuff? Blood Serum or Plasma Leukocytes, Platelets and RBC Mononuclear Cells Polymorphonuclear leukocytes (or Granulocytes) Serum Proteins Immunoglobulins Complement Clotting factors Many others Lymphocytes (T cells, B cells & NK cells) Monocytes Neutrophils Eosinophils Basophils

What are the effector functions? Antibody-Mediated Ways to Destroy the Target Complement activation Agglutination Neutralization Mask receptors Antibody-mediated cellular cytotoxicity (ADCC) Opsonization and phagocytosis Cell-Mediated Cytotoxic T-Lymphocyte Natural Killer Cells Antibody-mediated cellular cytotoxicity (ADCC)

Hypersensitivity Reactions When a good response goes terribly bad Hypersensitivity Reactions Reactions that are detrimental to the host The result of autoimmunity An atypical immune response An inability to eliminate a pathogen The tissues become a carrier for a hapten Transplanted tissues are recognized