Structure of the Immune System and the Lymphatic System

Introduction

• Overview of immune cells covered previously.
• Focus on the lymphatic system's role in the immune system.
• Purpose: To understand how immune cells are organized and activated.

Importance of the Lymphatic System

• Connects with the circulatory system; returns interstitial fluid to the bloodstream.
• Lymphatic system is crucial for immune activation.
• Immune cells need to recognize antigens and receive co-stimulatory signals.
• B and T lymphocytes each recognize one specific antigen.
• Challenges in immune activation due to multicellular organism complexity.

Components of the Lymphatic System

Lymph

• Fluid bathing tissues, contains waste, debris, pathogens.

Lymph Nodes

• Strategic sites for immune cell interaction.
• Structure: Protective capsule, afferent vessels, sinuses lined with macrophages and dendritic cells.
• Compartmentalized into cortex and T cell zones.
• B cell zone (follicles) and T cell zone (deep in the node).
• Dendritic cells present antigens to T cells.

Spleen

• Largest lymphatic organ.
• Functions:
  • Removes old red blood cells (red pulp).
  • Filters pathogens from blood (white pulp).
• Structure: Red pulp (Cords of Billroth, venous sinus), white pulp (T cell zones, B cell follicles).

Thymus

• Site for T cell development.
• Largest and most active during early life stages.
• Has cortex and medulla corresponding to T cell maturity stages.

Mucosa-Associated Lymphoid Tissues (MALT)

• Locations: Digestive tract, airways, urogenital tract, etc.
• Protects mucosal surfaces from infection.
• Specialized features like M cells in GALT for antigen sampling.
• Produces IgA antibodies to prevent excessive immune responses.

Function and Immune Response

• Immune cells circulate and interact at strategic sites.
• Activation occurs through antigen recognition and co-stimulation.
• Special mechanisms in place to prevent overactive responses.

Conclusion

• Detailed understanding of lymphatic system's role in immunity.
• Upcoming focus on inter-cellular communication among immune cells.