Vaccines

Humoral Immune Response

• Involves the production of antibodies by B cells in response to antigens.

  • Antigen (1st exposure):

  • Recognized and taken up by antigen-presenting cells.

    • The antigen-presenting cell processes the antigen and presents it to T cells.

  • B cells become activated by the recognition of the antigen alongside signals from Helper T cells.

    • Helper T cell: Activates B cells through cytokines.

    • This activation leads to two significant outcomes:

      • Plasma cells: Produce antibodies specific to the antigen.

      • Memory B cells: Store the information for a faster response upon re-exposure to the same antigen.

Cell-Mediated Immune Response

• Primarily involves cytotoxic T cells that target infected or malignant cells.

  • Key Components:

  • Cytotoxic T cell: Recognizes and destroys infected cells and certain cancer cells.

  • Upon second exposure:

    • Gives rise to Memory cytotoxic T cells: Provides rapid response to previously encountered antigens.

    • Active cytotoxic T cells: Execute defense mechanisms.

  • Functions of immune responses:

  • Defend against extracellular pathogens: Antibodies and B cells play a crucial role here.

  • Defend against intracellular pathogens and certain cancers: T cells are primarily responsible for this defense mechanism.

Vaccination Statistics

Annual Deaths from Measles and Polio in the U.S.

• Annual deaths from measles in the U.S.:

  • Data not specified in exact numerical format but referenced a decline post-vaccination introduction.

• Annual deaths from polio in the U.S.:

  • 3,500 in earlier years reported.

  • Significant reduction following vaccine introduction in 1988.

Countries that Have Eliminated Polio

• Graphical representation shows a significant decline in cases by year from 1950 to 2015.

Vaccine Rates of Measles Vaccination for Infants in 2014:

• 90-100%: High vaccination coverage.

• 80-89%: Moderate coverage.

• 50-79%: Lower coverage.

• <50%: Very low vaccination coverage.

• Data not available for certain regions.

• Overall, vaccination programs have significantly reduced deaths from various infections.

Immunization Methods

Traditional Vaccines

• Mechanism of action: The protection offered by a secondary immune response forms the foundation of immunization.

  • Antigens: Substances that induce an immune response when introduced into the body.

  • Types of antigens introduced include:

    • Inactivated bacterial toxins.

    • Killed or weakened pathogens.

    • Genes encoding microbial proteins.

    • Cytotoxic T-cell: Key component in combating infected cells.

mRNA Vaccines

• Virus Vector DNA and mRNA Vaccines:

  • Replication-Defective Virus Vector DNA:

  • Contains genetic material encoding for antigens, such as the coronavirus spike protein.

  • Mechanism of Action:

  • DNA is injected into host cells, leading to transcription and translation into spike proteins.

  • mRNA Vaccine: Encased in a lipid nanoparticle for cellular entry.

  • Generates peptide fragments of the spike protein that evoke immune response.

• Host Cell Nucleus: Site for DNA processing.

Development of Self-Tolerance

• Immature lymphocytes: T-cells and B-cells that react against self-antigens are either eliminated or inactivated during development.

• Mature Lymphocytes: Respond only to foreign antigens while distinguishing them from self-antigens.

Key Terms

• Apoptosis: The process of programmed cell death that eliminates potentially harmful self-reactive lymphocytes.

• Anergy: A state in which a lymphocyte cannot respond to an antigen, ensuring self-tolerance.

Autoimmune Diseases

• Definition: Autoimmune diseases occur when the immune system loses tolerance for self and mistakenly targets its own tissues.

  • Examples of Autoimmune Diseases:

  • Systemic lupus erythematosus: Immune system produces antibodies against DNA from the breakdown of cells, leading to conditions such as rashes, fever, arthritis, and kidney dysfunction.

  • Rheumatoid arthritis: Affects joints and connective tissues.

Susceptibility to Autoimmune Disorders

• Factors contributing to susceptibility include:

  • Genetics: Family history and hereditary predisposition.

  • Gender: Certain autoimmune diseases are more prevalent in women than men.

  • Environment: Environmental factors may trigger onset.

Autoimmune Disease Examples by Affected Systems

• Nervous System:

  • Multiple Sclerosis

  • Guillaun-Barre Syndrome

• Skin:

  • Psoriasis

  • Vitiligo

  • Eczema

  • Scleroderma

• Gastrointestinal Tract:

  • Celiac disease

  • Crohn's disease

  • Ulcerative colitis

• Endocrine:

  • Diabetes Type 1

  • Thyroiditis (Hashimoto's Disease)

  • Graves' Disease

• Musculoskeletal:

  • Rheumatoid Arthritis

  • Ankylosing Spondylitis

  • Polymyalgia Rheumatica

  • Muscular Dystrophy

  • Fibromyalgia

• Hematologic:

  • Leukemia

• Other:

  • Autism

  • Hemolytic anemia

Causes and Treatment of Autoimmune Diseases

Causes

• Development failures in B- and T-cell lines lead to cells not being eliminated that react against body’s own antigenic features.

• Infections that present antigens similar to normal body tissues may confuse the immune system leading to autoimmunity.

Treatment Approaches

• Weakening the Immune System: Employing immunosuppressants to reduce the activity of the immune system.

• Symptom Management: Treating the symptoms associated with the autoimmune disease to improve quality of life.