Overview

Immunology is the branch of biomedical science concerned with the study of the immune system, its structure, function, disorders, and interactions with pathogens. The immune system is a complex network of cells, tissues, and molecules that protects organisms from infection and disease.

Components of the Immune System

1. Innate Immunity

  • Physical Barriers: Skin, mucous membranes
  • Cellular Defenses: Macrophages, neutrophils, dendritic cells, natural killer (NK) cells
  • Chemical Defenses: Lysozyme, complement proteins, interferons

2. Adaptive Immunity

  • Humoral: B cells produce antibodies (immunoglobulins)
  • Cell-mediated: T cells (Helper CD4+, Cytotoxic CD8+)
  • Memory: Long-lived cells for rapid response upon re-exposure

Diagram: Immune System Overview

Immune System Overview

Immune Response Steps

  1. Recognition: Pathogen-associated molecular patterns (PAMPs) detected by pattern recognition receptors (PRRs).
  2. Activation: Cytokine release, antigen presentation.
  3. Effector Phase: Elimination of pathogens via phagocytosis, cytotoxicity, or antibody neutralization.
  4. Resolution: Downregulation of immune response, tissue repair.
  5. Memory Formation: Creation of memory B and T cells.

Recent Breakthroughs

1. CRISPR-Based Immunotherapies

  • CRISPR technology is being harnessed to engineer immune cells to target cancer and viral infections more precisely.

2. Microbiome-Immune Interactions

  • Recent studies show gut microbiota modulates immune responses, influencing susceptibility to autoimmune diseases and allergies.

3. Universal Influenza Vaccines

  • mRNA platforms are being developed to create vaccines that elicit broad and durable immunity against multiple flu strains.

Citation

  • Zhou, Y., et al. (2022). “CRISPR-engineered T cells in cancer immunotherapy.” Nature Reviews Immunology, 22(8), 495-507.

Memory Trick

“B for Body, T for Team”

  • B cells: Think “Bodyguards” – they patrol and produce antibodies.
  • T cells: Think “Team leaders” – they coordinate and execute cellular attacks.

Common Misconceptions

  1. Immunity is Absolute: Immunity is not always complete; it can wane over time or fail against mutated pathogens.
  2. Antibiotics Boost Immunity: Antibiotics target bacteria, not viruses, and do not enhance immune function.
  3. Vaccines Cause Disease: Vaccines use inactivated or attenuated agents; they do not cause the disease but stimulate protective immunity.
  4. All Immune Responses Are Beneficial: Overactive immunity (autoimmunity, allergies) can damage tissues.

Surprising Facts

  1. Bacteria in Extreme Environments: Some bacteria thrive in deep-sea vents and radioactive waste, challenging the immune system’s adaptability.
  2. Immune Cells Have Memory Beyond Pathogens: Trained immunity in innate cells can “remember” past exposures, altering future responses.
  3. Cancer Cells Evade Immunity by Mimicry: Tumors can express proteins that make them appear as “self” to immune cells, avoiding detection.

Unique Details

Antigen Presentation

  • Dendritic cells are primary antigen-presenting cells (APCs), bridging innate and adaptive immunity.
  • MHC class I presents to CD8+ T cells, MHC class II to CD4+ T cells.

Immunological Synapse

  • Specialized junction between a T cell and APC, facilitating signal transduction and activation.

Immune Privilege

  • Certain sites (e.g., brain, eyes, testes) limit immune responses to prevent tissue damage.

Immunology in Extreme Environments

  • Deep-sea bacteria: Possess unique surface molecules, requiring specialized PRRs for recognition.
  • Radioresistant microbes: Deinococcus radiodurans can survive intense radiation, with DNA repair mechanisms that challenge immune detection.

Clinical Applications

  • Immunotherapy: Monoclonal antibodies, checkpoint inhibitors, CAR-T cells.
  • Autoimmune Disease Management: Targeted biologics (e.g., anti-TNF agents).
  • Transplantation: Immunosuppressants to prevent rejection.

Common Laboratory Techniques

  • Flow Cytometry: Quantifies and sorts immune cells by markers.
  • ELISA: Detects antibodies or antigens in samples.
  • Western Blot: Identifies specific proteins.

Reference

  • Zhou, Y., et al. (2022). “CRISPR-engineered T cells in cancer immunotherapy.” Nature Reviews Immunology, 22(8), 495-507. Link

Diagram: Adaptive Immune Response

Adaptive Immune Response

Summary Table

Component Key Cells Main Function Example
Innate Immunity Macrophages, NK Immediate defense Phagocytosis
Adaptive B, T cells Specific, memory Antibody production
Barrier Skin, mucosa Prevent entry Lysozyme in tears

Further Reading

End of Notes