Immunology Overview: Lymphokines and Antibodies

Lymphokines

• Regulate the immune response
• Control the growth, mobility, and differentiation of leukocytes

Immune System Regulation

• Suppressor cells: Inhibit immune responses
• Immune response genes: Control individual immune responses
• Antigen regulation: Regulate amount and type of antigens
• Passive immunity: Transfer of antibodies, providing temporary protection

Antibody Types

• Autoantibodies: Target the body's own cells & tissues
• Alloantibodies: Attack the tissues of other individuals
• Heteroantibodies: Attack non-human antigens

Immunoglobulin Classes

• IgG: Most common type, found in blood and tissues; protects against bacteria, viruses, and toxins
• IgA: Found in mucosal areas (e.g., respiratory and gastrointestinal tracts) and body secretions; protects against infections
• IgM: First antibody produced in response to infection; activates complement
• IgD: Found on the surface of B cells; role in B cell activation
• IgE: Involved in allergic and parasitic infections

Immunoglobulin Structure

• Heavy chain: 2 polypeptide chains with approximately 450 amino acids
• Light chain: 2 polypeptide chains with approximately 214 amino acids
• Constant region: The portion of the antibody’s polypeptide chain that determines its class
• Variable region: The portion of the antibody that binds to a specific antigen; recognizes and interacts with specific antigens
• Hinge region: Flexible region connecting the Fab and Fc regions; allows antibodies to bind to antigens in different conformations
• Fab (Fragment antigen-binding): The portion of the antibody that binds to the antigen; contains the variable region to recognize antigens
• Fc (Fragment crystallizable): The portion of the antibody that interacts with other immune cells; contains the constant region, determining the antibody's effector function
• J chain: A small polypeptide chain that links two IgA molecules together to form dimers, or connects IgM molecules to form pentamers
• Disulfide bond: A covalent bond that stabilizes the immunoglobulin structure by joining polypeptide chains

Primary vs. Secondary Response

• Primary response: Initial encounter with an antigen; slower response with lower antibody production
• Secondary response: Subsequent exposure; faster, stronger response due to memory cells; higher antibody levels

Immunity Types

• Passive active immunity: Transfer of antibodies from another individual (e.g., maternal antibodies)
• Natural active immunity: Exposure to an infectious agent; results in long-lasting specific immunity
• Artificial passive immunity: Injection of pre-formed antibodies; provides temporary protection
• Artificial active immunity: Vaccination with weakened or attenuated pathogens or antigens; leads to long-lasting immunity

Complement Function

• Destroy pathogens: Lyses cells and triggers inflammatory responses
• Enhance phagocytosis: Opsonize pathogens
• Trigger inflammation: Recruit immune cells to the site of infection
• Eliminate immune complexes: Clear antigen-antibody complexes from circulation

Complement Pathways

• Classical pathway: Activated by antigen-antibody complexes
• Alternative pathway: Activated by microbial surfaces and foreign particles

Granuloma Formation

• Occurs when the immune system cannot contain an infection
• Formation of a mass of macrophages, lymphocytes, and other cells

Inflammation

• Definition: Nonspecific response to injury or infection
• Characteristics: Redness, swelling, pain, heat, and loss of function

Classical vs Alternative Complement Pathways

• Classical pathway: Requires antigen-antibody complexes to initiate activation; more specific and slower
• Alternative pathway: Activated by microbial surfaces and foreign particles; less specific and faster

Complement Biological Activities

• Lysis of cells directly destroys bacteria and other pathogens
• Opsonization coats pathogens, enabling phagocytes to recognize and engulf them
• Inflammation recruits immune cells like neutrophils to the site of infection
• Immune complex clearance removes antigen-antibody complexes from the circulation

Immune Response to Infections

• Bacterial infections: Antibody production, complement activation, phagocytosis
• Toxigenic bacterial infections: Neutralization of toxins by antibodies
• Viral infections: Antibody production (neutralization of viruses), cell-mediated immunity (killing of infected cells)
• Parasitic infections: Eosinophils, IgE, and mast cells play a crucial role; hypersensitivity reactions
• Fungal infections: Adaptive immune responses, macrophages, and neutrophils; granuloma formation

Tolerance and Immunosuppression

• Immunologic Tolerance: A state of unresponsiveness to a specific antigen; prevents the immune system from attacking self-antigens.
• Peripheral tolerance: Mechanism that eliminates or inactivates self-reactive immune cells
• Immunosuppression: Suppression of the immune response; used in organ transplantation and autoimmune diseases
• Immunopotentiation: Enhancement of the immune response; used to treat certain infections and cancers
• Suppressor cells: Specialized immune cells that regulate the immune response and suppress the activation of other immune cells
• Proliferate: Rapid and uncontrolled growth of cells
• Neoplasm: Abnormal growth of cells
• Benign: Non-cancerous; does not spread
• Malignant: Cancerous; spreads to other tissues or organs
• Dyscrasia: Disorder of the blood or bone marrow
• Aplasia: Defective formation or lack of development
• Metastatic/Metastasis: The spread of cancer cells to other parts of the body

Immunoproliferative Diseases

• Leukemia: Cancer of the blood-forming cells in bone marrow
• Lymphomas: Cancers that affect the lymphatic system
• Plasma cell dyscrasias: Disorders involving proliferation of plasma cells:
  • Multiple myeloma: Cancer of plasma cells
  • Waldenstrom's macroglobulinemia: Cancer involving the production of IgM antibodies
  • Heavy chain disease: Disorder involving the production of abnormal heavy chain antibodies
  • Amyloidosis: A condition where amyloid protein deposits in tissues

Immunodeficiency Diseases

• T cell deficiency: Defective T cell function; impaired cell-mediated immunity
• B cell deficiency: Defective B cell function; impaired antibody production
• SCID (severe combined immunodeficiency): Defects in both T and B cell function; severe impairment of the immune system
• Phagocytic dysfunction: Defective phagocytic cells; impaired ability to engulf and destroy pathogens
• Neutropenia: Low neutrophil count; increases susceptibility to bacterial infections
  • Congenital neutropenia: Inherited form of neutropenia
  • Acquired neutropenia: Develops due to certain medications or infections
  • Cyclic neutropenia: Neutrophil counts fluctuate over time
• Complement deficiency: Defective complement system; increased susceptibility to infections

Hypersensitivity Reactions

• Type I: Immediate hypersensitivity; allergies; mast cell degranulation
• Type II: Cytotoxic hypersensitivity; antibody-dependent cell-mediated cytotoxicity; destruction of cells
• Type III: Immune complex hypersensitivity; formation of immune complexes; damage to tissues
• Type IV: Delayed-type hypersensitivity; cell-mediated immunity; T cell activation and release of cytokines

HLA System

• Involves more than 200 genes
• Functions: Tissue typing and immune regulation
• Importance: Tissue compatibility for transplantation, susceptibility to certain diseases

Transplantation

• Eligible tissues/organs: Kidneys, heart, liver, lungs, pancreas

Transplant Complications

• Rejection: Immune response against the transplanted organ triggered by the recipient's immune system
• GvHD (graft-versus-host disease): Immune cells in the donated graft attack the recipient's tissues

Oncogenes & Tumor Antigens

• Oncogene: A gene that can cause cancer; often mutated forms of normal cellular genes (proto-oncogenes).
• Anti-oncogene: A gene that normally suppresses tumor growth; loss of function can trigger cancer
• Viral oncogene: A gene from a virus that can transform a normal cell into a cancerous cell
• Tumor antigen: An antigen present on the cell surface of a tumor; can be used to identify and target cancer cells

Tumor Markers

• CEA (Carcinoembryonic antigen): Found in some cancers, including colorectal cancer
• AFP (Alpha-fetoprotein): Found in some cancers, including liver and testicular cancer
• PSA (Prostate-specific antigen): Indicates prostate cancer
• Ectopic: Production of a hormone or protein by a tissue that normally does not produce that substance

Types of Tumor Antigens

• Tumor-associated antigens: Found on normal cells, but expressed at higher levels in tumor cells; e.g., CEA
• Tumor-specific antigens: Found only on tumor cells; e.g., mutated proteins
• Differentiation antigens: Found on certain types of cells during their development and differentiation; can be used to diagnose specific types of cancer
• Onco-viral antigens: Viral proteins expressed in cells infected by cancer-causing viruses; example: HPV proteins in cervical cancer

Test your knowledge of lymphokines, immune system regulation, and antibody types with this comprehensive quiz. Explore the role of immunoglobulin classes in immune responses and how they protect the body against various pathogens. Perfect for students studying immunology or related subjects.