Study guide

Immune System Overview

  • Self vs. Non-Self Recognition:

    • The immune system distinguishes between self (healthy cells) and non-self (pathogens) using pattern recognition receptors (PRRs) and major histocompatibility complex (MHC) molecules.

  • Innate vs. Adaptive Immunity:

    • Innate Immunity: General, nonspecific defense mechanisms that respond rapidly to pathogens (e.g., skin, phagocytes).

    • Adaptive Immunity: More specific and slower response, involves B cells (antibodies) and T cells (cellular immunity).

Innate Immunity

  • First-Line Defense:

    • Physical barriers: Skin, mucous membranes, cilia.

    • Chemical barriers: Stomach acid, lysozyme in tears and saliva.

    • Cellular components: Phagocytes like neutrophils and macrophages.

  • Inflammation & Complement System:

    • Inflammation: Response to injury or infection, involving redness, heat, swelling, and pain, aimed at eliminating pathogens.

    • Complement System: A set of proteins that enhance immune responses, can directly kill pathogens or mark them for destruction by phagocytes.

Adaptive Immunity

  • B Cells and T Cells:

    • B Cells: Produce antibodies that neutralize pathogens or mark them for destruction.

    • T Cells:

      • Helper T Cells: Activate B cells and cytotoxic T cells.

      • Cytotoxic T Cells: Destroy infected or cancerous cells.

  • Antigen-Presenting Cells (APCs) & MHC:

    • APCs: Dendritic cells, macrophages, and B cells present antigens to T cells.

    • MHC Molecules: Class I MHC present to cytotoxic T cells (for intracellular pathogens), and Class II MHC present to helper T cells (for extracellular pathogens).

  • Antibodies:

    • Y-shaped proteins that bind to antigens, neutralizing or marking them for destruction.

    • Types include IgG (most abundant), IgA (mucosal immunity), IgM (early response), IgE (allergic responses), and IgD (B cell activation).

Regulation of Immune Responses

  • Control of Immune Responses:

    • Negative Feedback: Regulatory T cells (Tregs) suppress immune responses to prevent overreaction.

    • Immune Tolerance: The immune system learns to ignore self-antigens during development.

  • Failure of Regulation:

    • Autoimmunity: Immune system mistakenly targets self-cells (e.g., Type 1 diabetes, rheumatoid arthritis).

    • Immune Tolerance Breakdown: Leads to autoimmune diseases or immunodeficiency.

Immune Evasion by Pathogens

  • Evasion Strategies:

    • Bacteria: Antigen variation, producing inhibitors of immune signaling, hiding within host cells.

    • Viruses: Mutating rapidly (e.g., influenza), inhibiting antigen presentation (e.g., HIV), latency (e.g., herpesviruses).

  • Persistence of Infections:

    • Some pathogens, like HIV and influenza, evade immune responses by mutating and altering surface proteins or integrating into the host genome.

Autoimmune Diseases & Immunodeficiency

  • Autoimmune Diseases:

    • Occur when the immune system attacks the body’s own cells. Examples include lupus, MS, and rheumatoid arthritis.

  • Immunodeficiency:

    • Primary: Genetic disorders (e.g., SCID).

    • Secondary: Acquired, such as HIV/AIDS, where the immune system is weakened.

Gene Expression in Immunity

  • Immune Function at the Genetic Level:

    • Gene expression is controlled through transcription factors that activate or suppress the immune genes.

  • Gene Modifications:

    • CRISPR: Can be used to edit genes involved in immune responses, like engineering immune cells to target cancer.

    • Epigenetics: DNA modifications without changing the sequence, influencing immune cell function.

Applied Immunology & Biotechnology

  • Vaccines:

    • How Vaccines Work: Stimulate the immune system by presenting antigens (from weakened or killed pathogens or their parts) to create immunity.

    • Long-Term Immunity: Results from memory cells (B and T cells), which recognize and respond faster to future infections.

  • Monoclonal Antibodies:

    • Definition: Laboratory-made antibodies designed to target specific antigens.

    • Uses: Treatment of diseases like cancer, autoimmune disorders, and infections.

ELISA Testing

  • What ELISA Tests For:

    • ELISA (Enzyme-Linked Immunosorbent Assay) detects specific proteins, antibodies, or antigens in a sample.

  • Types of ELISA:

    • Direct ELISA: Detects antigens using a labeled antibody.

    • Indirect ELISA: Detects antibodies against a specific antigen.

    • Sandwich ELISA: Captures the antigen between two layers of antibodies.

    • Competitive ELISA: Detects competition between antigen and a labeled reference antigen.

  • Applications of ELISA:

    • Medical Diagnostics: Detects infections, pregnancy, or autoimmune conditions.

    • Biotech Research: Studies immune responses and biomarker identification.