Basic Concepts of Immunology

Basic Concepts of Immunology

• Definition: Study of the immune system, which protects the body against pathogens.
• Components of the Immune System:
  • Innate Immunity:
    • First line of defense.
    • Non-specific responses, including barriers (skin, mucous membranes) and immune cells (macrophages, neutrophils).
  • Adaptive Immunity:
    • Specific responses to pathogens.
    • Involves lymphocytes (B-cells and T-cells) and memory cells.

Immune Cells

• B Cells:
  • Produce antibodies.
  • Differentiate into plasma cells and memory B cells upon activation.
• T Cells:
  • Helper T Cells (CD4+): Activate B cells and other immune cells.
  • Cytotoxic T Cells (CD8+): Destroy infected cells or cancer cells.
• Antigen-Presenting Cells (APCs):
  • Include dendritic cells and macrophages.
  • Present antigens to T cells to initiate adaptive response.

Antibodies

• Structure: Y-shaped proteins with variable and constant regions.
• Functions:
  • Neutralization: Block pathogen entry or activity.
  • Opsinization: Mark pathogens for destruction by phagocytes.
  • Activation of complement system: Leads to pathogen lysis.

Immune Responses

• Primary Response:
  • Occurs on first exposure to an antigen.
  • Slower and generates memory cells.
• Secondary Response:
  • Faster and more robust response upon re-exposure.
  • Memory cells rapidly proliferate and produce antibodies.

Cytokines

• Definition: Signaling molecules that mediate and regulate immunity.
• Types:
  • Interleukins (IL): Role in cell communication.
  • Tumor Necrosis Factor (TNF): Involved in systemic inflammation.
  • Interferons: Involved in antiviral responses.

Hypersensitivity Reactions

• Type I (Allergic): Immediate reaction; involves IgE antibodies (e.g., pollen allergy).
• Type II (Cytotoxic): Involves IgG/IgM antibodies against self-antigens (e.g., hemolytic anemia).
• Type III (Immune Complex): Deposition of antigen-antibody complexes (e.g., lupus).
• Type IV (Delayed-type): T-cell mediated response (e.g., contact dermatitis).

Immunization

• Active Immunization: Exposure to a pathogen (natural infection or vaccination); body produces antibodies and memory cells.
• Passive Immunization: Transfer of antibodies (e.g., maternal antibodies to infants).

Immune Disorders

• Autoimmune Diseases: Immune system mistakenly attacks the body (e.g., rheumatoid arthritis, type 1 diabetes).
• Immunodeficiency: Reduced function of the immune system (e.g., HIV/AIDS).
• Allergies: Hyperactive immune response to harmless substances.

Key Terms

• Antigen: Any substance that triggers an immune response.
• Pathogen: Disease-causing organism (e.g., bacteria, viruses).
• Immunology: Science of the immune system and its functions.

Immunology Basics

• The study of the immune system, protecting the body from pathogens.
• Two main branches: innate and adaptive

Innate Immunity

• The first line of defense, providing a non-specific barrier.
• Physical barriers like skin and mucous membranes.
• Immune cells like macrophages and neutrophils play a key role.

Adaptive Immunity

• Specific immune responses tailored to pathogens.
• Involves lymphocytes: B cells and T cells, responsible for generating memory cells.

B Cells

• Responsible for producing antibodies.
• Differentiate into plasma cells, producing high levels of antibodies, and memory B cells, for rapid responses upon re-exposure.

T Cells

• Helper T Cells (CD4+): Activate B cells and other immune cells
• Cytotoxic T Cells (CD8+): Destroy infected or cancerous cells

Antigen-Presenting Cells (APCs)

• Include dendritic cells and macrophages.
• Present antigens to T cells, initiating the adaptive response.

Antibodies

• Y-shaped proteins with variable and constant regions.
• Functions:
  • Neutralization: blocking pathogen entry or activity.
  • Opsonization: marking pathogens for destruction by phagocytes.
  • Activation of the complement system: leading to pathogen lysis.

Immune Responses

• Primary Response:
  • First exposure to an antigen.
  • Slower response with memory cell generation.
• Secondary Response:
  • Faster and more robust response upon re-exposure.
  • Memory cells allow for rapid antibody production.

Cytokines

• Signaling molecules mediating and regulating immunity.
• Types:
  • Interleukins (IL): crucial for cell communication.
  • Tumor Necrosis Factor (TNF): involved in systemic inflammation.
  • Interferons: critical for antiviral responses.

Hypersensitivity Reactions

• Exaggerated immune responses to harmless substances.
• Four types:
  • Type I (Allergic): immediate reaction with IgE antibodies (e.g., pollen allergies).
  • Type II (Cytotoxic): involving IgG/IgM antibodies against self-antigens (e.g., hemolytic anemia).
  • Type III (Immune Complex): antigen-antibody complex deposition (e.g., lupus).
  • Type IV (Delayed-type): T-cell mediated, delayed response (e.g., contact dermatitis).

Immunization

• Active Immunization: exposure to a pathogen (natural infection or vaccination); body produces antibodies and memory cells.
• Passive Immunization: transferring antibodies (e.g., maternal antibodies to infants).

Immune Disorders

• Autoimmune Diseases: immune system attacks the body's own tissues (e.g., rheumatoid arthritis, type 1 diabetes).
• Immunodeficiency: reduced or impaired immune system function (e.g., HIV/AIDS).
• Allergies: exaggerated immune response to harmless substances.

Key Terms

• Antigen: any substance triggering an immune response.
• Pathogen: disease-causing organism (e.g., bacteria, viruses).
• Immunology: the study of the immune system and its functions.

Explore the essential principles of immunology, focusing on the immune system's components. This quiz covers innate and adaptive immunity, including the roles of B cells, T cells, and antibodies. Test your understanding of how the immune system protects the body against pathogens.