Recording-2025-03-13T20:17:46.457Z

Difference Between Antigen and Pathogen

• Pathogen:

  • Defined as a disease-causing organism.

  • Example: bacteria, viruses, fungi, or parasites.

  • Generally considered harmful to the host organism.

  • Pathogens are recognized by the immune system.

• Antigen:

  • A specific marker found on pathogens.

  • Helps the immune system identify and respond to pathogens.

  • Not inherently harmful; it's a component of the pathogen.

  • The immune response targets antigens to eliminate pathogens.

Immune System Overview

• Innate Immunity:

  • Non-specific initial response to pathogens.

  • Key components: Toll receptors and pattern recognition receptors (PRRs).

  • Toll receptors function analogously to security cameras that detect pathogens.

  • They identify pathogen-associated molecular patterns (PAMPs).

Toll Receptors Activation

• When a pathogen invades, toll receptors:

  • Detect the pathogen.

  • Activate a signaling cascade involving P L kinase.

  • Phosphorylate cactus, an inhibitor protein that regulates immune responses.

  • This activation allows dorsal (an immune response factor) to enter the nucleus and promote the production of antifungal proteins.

Role of Key Immune Cells

Mast Cells

• Function: Early responders initiating inflammation.

• Location: Found in tissues near blood vessels.

• Actions:

  • Release histamine, causing blood vessels to become leaky.

  • Allows immune cells to enter the infection site.

  • Key to the initial inflammatory response, leading to common signs like redness and swelling.

Neutrophils

• Function: First line of defense in innate immunity.

• Actions:

  • Arrive after mast cells to attack pathogens directly.

  • Engage in phagocytosis (engulfing and digesting pathogens).

  • Release toxic granules that kill pathogens.

  • After fulfilling their role, they self-destruct, contributing to pus.

Macrophages

• Function: Clean-up crew for dead cells and pathogens.

• Actions:

  • Arrive after neutrophils to clear debris via phagocytosis.

  • Release cytokines to signal for more immune responses.

  • Present antigens to activate the adaptive immune system, particularly T cells.

Cytokines vs. Chemokines

• Cytokines:

  • Small proteins regulating immune responses.

  • Important for communication among immune cells.

• Chemokines:

  • A subset of cytokines that directs the movement of immune cells (chemotaxis).

  • Facilitate the migration and positioning of immune cells to sites of infection.

Allergic Reactions

• Mast cells can cause allergy symptoms when they respond to harmless substances (e.g., pollen).

• Over-release of histamine leads to symptoms like swelling, runny nose, and itchy skin.

Summary of Immune Response Timeline

1. Mast Cells react first by releasing histamine to signal inflammation.

2. Neutrophils are deployed for initial attack on pathogens through phagocytosis.

3. Macrophages arrive later to clean up and present antigens, activating T cells for a more specific response.

Importance of Clean-Up in Immune Response

• If macrophages do not clear the dead cells:

  • Immune response may not properly conclude.

  • Can lead to prolonged inflammation and pain, hindering recovery.

Questions for Further Discussion

• What role do mast cells play in initiating an immune response and in allergies?

• How do cytokines and chemokines differ in their functions?

• Why is the removal of dead cells crucial in terminating an immune response?