Bio lecture 03/10

Overview of Innate Immunity

• Focus on innate immunity and inflammatory response

• Revisit the signaling pathway in Drosophila

Learning Outcomes

• Understanding the inflammatory response

• Recognizing the pathways activated by pathogen recognition

Drosophila Immune Response

• Activation of Innate Immunity:

  • Flies recognize fungal pathogens through specific surface patterns.

  • Pathway activation examples: Toll receptors, Pele kinase, cactus, and dorsal proteins.

• Signaling Cascade:

  • Pathogen Activation: Fungal pathogen detected by Toll receptors.

  • Intracellular Signaling: Toll receptors activate Pele kinase, leading to the phosphorylation of cactus.

  • Degradation of cactus: This allows dorsal protein to enter the nucleus and activate antifungal gene transcription.

Signaling Pathways

• Illustration of Pathways:

  • Arrow diagrams used to denote activation processes.

  • Think about effects of mutations at different points in the pathway.

• Application to Humans:

  • Similar innate immune response in humans with pattern recognition receptors like Toll-like receptors (TLRs).

  • Reinforces the concept of evolutionary conservation in immune systems.

Innate vs. Adaptive Immunity

• Key Characteristics of Innate Immunity:

  • No memory involved; consistent response to infections.

  • Example: Physical barriers (skin, mucus) and mucus traps pathogens.

• Overview of Adaptive Immunity:

  • Involves B-cells and T-cells; develops over time and offers memory.

  • Adaptive immunity integrates signals from the innate response to amplify future defense against recognized pathogens.

Inflammatory Response Mechanism

• Initial Response:

  • Wound exposure followed by recognition of bacteria by macrophages.

  • Platelets form clots to reduce blood loss and prevent infection at wound sites.

• Role of Macrophages:

  • Perceive infection and secrete chemokines to recruit other immune cells.

  • Chemokines: Attract additional immune cells to the site of injury.

Cytokine Release and Inflammation

• Mast Cell Activation:

  • Release of histamines leads to vasodilation and increased permeability of blood vessels.

  • Increased blood flow to promote immune cell access.

• Neutrophil Function:

  • Newly recruited neutrophils and macrophages engage in phagocytosis to destroy pathogens and secrete further signaling molecules (e.g., prostaglandins for fever induction).

Consequences of Inflammation

• Physical Symptoms:

  • Swelling, redness, and warmth at infection site.

  • Mucus production like runny nose and tearing to remove pathogens.

• Potential for Hyperactive Responses:

  • In some cases, excess inflammation can occur, leading to tissue damage.

Importance of the Innate Response

• Goals of Innate Immunity:

  • Restore physical barrier, limit damage, eliminate pathogens, and alert adaptive immune response.

• Understanding the initial innate reactions helps in comprehending broader immune functionalities.

Anti-histamines and Immune Drugs

• Common Treatments:

  • Anti-histamines to alleviate symptoms dampen the immune response.

  • Acknowledgment of the discomfort caused by natural inflammation responses.

Autoimmunity and Immune Dysfunction

• Dysregulation of Immune System:

  • Autoimmune diseases arise when the immune system misidentifies self-tissues as foreign.

  • Reflects on importance of regulatory mechanisms in immune responses.

Human Microbiome and Immune Function

• Concept of Microbiome:

  • Relationship between human cells and diverse microbial populations.

  • Microbiomes vary across body environments, influencing health outcomes.

• Research Significance:

  • Understanding how birth processes (vaginal vs c-section) can influence the microbiome and future disease risks.