Immune System Overview Lecture Notes

Introduction to the Immune System

• The immune system is crucial for defending against pathogens such as bacteria, viruses, fungi, parasites, and cancer cells.
• Prevention: Skin and mucous membranes act as barriers to prevent pathogen entry.

Types of Immunity

• Specific Immunity:
  • Acquired through exposure or vaccination.
  • Memory is developed for faster response upon re-exposure.
  • Vaccines help in building immunity without disease symptoms.
  • Important to balance vaccination for personal and public health.
• Nonspecific Immunity:
  • Immediate response to pathogens.
  • Involves inflammatory response, neutrophils, and monocytes.
  • Symptoms include swelling, redness, and fever.
  • Fever can help fight off infections as higher temperatures can inhibit the growth of certain pathogens.

Immune System Components

• Cells: Neutrophils, monocytes, lymphocytes, macrophages, natural killer cells.
  • Macrophages act as antigen-presenting cells (APCs).
  • Natural killer cells target tumors using perforins.
• Soluble Factors: Antibodies, cytokines.
  • Cytokines are signaling proteins that regulate immunity and inflammation.

Immune Response Process

• Inflammatory Response:
  • Tissue damage leads to vasodilation, increased blood flow, and permeability.
  • Neutrophils and monocytes are recruited to the site.
  • Systemic responses such as fever might occur.
• Specific Immune Response:
  • Involves antigen recognition by T cells and B cells.
  • T cells mature in the thymus; B cells in the bone marrow.
  • Helper T cells coordinate the immune response by activating other immune cells.
  • T killer cells destroy infected or abnormal cells.
  • Suppressor T cells help downregulate the immune response.

Major Histocompatibility Complex (MHC)

• MHC molecules present on all cells to help immune cells distinguish self from non-self.
• MHC-antigen complex signals T cells for a targeted immune response.

Antibody Function

• Neutralize pathogens by binding to antigens.
• Facilitate pathogen destruction through agglutination and complement activation.

Types of Antibodies

• IgG: Found in body fluids.
• IgA: Present in mucous membranes.
• IgM: Found in blood and lymph fluid.
• IgE: Associated with allergic responses.
• IgD: Least understood but important in certain conditions.

Immunization

• Active Immunization: Natural exposure or vaccination that builds long-term immunity.
• Passive Immunization: Transfer of antibodies from another source (e.g., maternal antibodies, anti-venom).

Lymphoid Organs

• Primary Lymphoid Organs: Bone marrow and thymus for immune cell maturation.
• Secondary Lymphoid Organs: Lymph nodes, spleen, and mucosa-associated lymphoid tissues for immune response.
  • Lymph nodes filter lymph and house immune cells.
  • Spleen filters blood and recycles red blood cells.
  • Peyer's patches in the gut monitor intestinal bacteria and contribute to gut immunity.

Conclusion

• The immune system involves a complex interaction between cells, proteins, and organs to protect the body from pathogens.
• Understanding the immune system's components and functions is essential for recognizing how it defends the body and its role in health and disease management.