Chapter-1-Intro-to-Immunoserology

Introduction to Immunology and the Immune System

• Overview of immunology as the study of the immune system's response to foreign substances.

Course Outline

• Key Topics Covered:

  • Immunity and immunization

  • Innate vs adaptive immunity

  • Cells of the innate and adaptive immune systems

  • Organs of the immune system

Definition of Terms

• Immunology: Study of host responses to foreign substances with a focus on:

  • Discrimination between self and non-self

  • Elimination of non-self components such as infectious agents

  • Medical consequences of these mechanisms' failure or exaggeration

• Antigens: Foreign substances inducing host immune response.

• Antibody: Glycoprotein produced by the body that neutralizes and eliminates antigens.

• Immunity: Resistance to infection.

• Attenuation: Making a pathogen less virulent through methods like heat or chemicals.

Types of Immunity

• Innate Immunity (NI):

  • Non-specific and immediate response using body’s natural functions.

  • Responses are identical regardless of the pathogen.

• Adaptive Immunity (AI):

  • Specific responses requiring prior exposure to the pathogen.

  • Involves lymphocyte activation.

• Serology: Study of antigen-antibody reactions in vitro, applying immunologic principles for disease monitoring.

Early History of Immunology & Serology

• 429 BC: Thucydides notes smallpox immunity.

• 900 A.D.: Chinese variolation using smallpox scabs.

• 1717: Lady Mary Montagu introduces variolation to Europe.

• 1798: Edward Jenner's cowpox vaccination for smallpox.

• 1879: Louis Pasteur’s germ theory discovery and production of attenuated vaccines.

• 1882: Robert Koch isolates anthrax virus.

• 1883: Metchnikoff's hypothesis of cellular immunity through phagocytosis.

• 1890s: Emil von Behring’s humoral immunity studies; masters of agglutination and precipitation techniques.

• 1903: Almroth Wright links humoral and cellular factors in immunity.

• 1920: Introduction of vaccines for diphtheria, tetanus, and tuberculosis.

• 1930: Karl Landsteiner’s discovery of ABO blood types and haptens.

Cells of the Immune System

• Leukocytes (WBC): Role in innate/adaptive immunity; found in peripheral blood.

  • Types of WBCs:

    • Neutrophils

    • Eosinophils

    • Basophils

    • Monocytes

    • Lymphocytes

Specific Leukocyte Types

Neutrophils

• 50-70% of WBCs.

• Functions: First responders and phagocytosis, responding to infection via chemotaxis.

Eosinophils

• 1-3% of circulating WBCs.

• Functions: Neutralize basophil and mast cell products; assist against helminths.

Basophils

• <1% of WBCs.

• Functions: Induce allergic responses and release histamine.

Monocytes (Macrophages)

• 4-10% of WBCs.

• Functions: Phagocytosis and transition into macrophages in tissues.

• Various names based on location: Kupffer cells in liver, microglial cells in brain.

Lymphocytes

• 20-40% of WBCs; main actors in adaptive immunity.

• Subtypes include T cells (cell-mediated immunity), B cells (humoral immunity), and NK cells (innate immunity).

Key Tissue Cells in Immunity

Macrophages

• Initiate/regulate immune responses, conducting various immune functions across multiple tissues.

Mast Cells

• Similar to basophils; role in allergic reactions and antigen presentation.

Dendritic Cells

• Most effective antigen-presenting cells, crucial for signaling other immune cells.

Organs of the Immune System

Primary Lymphoid Organs

1. Bone Marrow: Main source of hematopoietic stem cells; B cell maturation location.

2. Thymus: T cell maturation organ; where thymocytes develop.

Secondary Lymphoid Organs

1. Lymph Nodes: Filters lymph fluid, generates B cell memory.

2. Spleen: Largest secondary lymphoid organ; contains red and white pulp.

3. MALT (Mucosa-associated lymphoid tissue): Non-encapsulated lymphoid tissue in mucosal areas.

4. Tonsils: Respond to pathogens entering the respiratory and alimentary tracts.

5. CALT (Cutaneous-associated lymphoid tissue): Immune cells located in skin layers.

Functions of Organs

• Primary: Source of immune cells, maturation of T and B lymphocytes.

• Secondary: Filters blood, facilitates interactions among immune cells.

Summary

• Innate immunity: General resistance to infections.

• Adaptive immunity: Specific immune responses, relying on memory and lymphocyte activation.

• Origin of all blood cells is from hematopoietic stem cells in the bone marrow.

• NK cells respond to infected/cancerous cells without previous exposure.

• Primary lymphoid organs: Bone marrow and thymus; Secondary: Spleen, lymph nodes, MALT, CALT.