Autoimmunity ppt

Mid-Semester Exam Details

• Date: Tuesday, March 18th, 2025

• Format: In-person

• Location: Highfield Campus (see timetable for specific room and time)

• Exam Structure: 40 questions covering innate and adaptive immunity

• Special Consideration: Extra time available for eligible students via student office

• Instructions: Students must remain seated if they finish early.

Autoimmune Diseases

• Common Autoimmune Diseases:

  • Multiple sclerosis

  • Systemic Lupus Erythematosus

  • Rheumatoid arthritis

Learning Objectives

• Breakdown of immune system functioning leading to autoimmune diseases.

• Plasticity of the immune system regarding pathogen recognition and its consequences.

• Key Points:

  • Effectors of acquired immunity: antibodies, T-cells

  • Antigen presentation by professional antigen-presenting cells (APCs)

  • Mechanisms of tolerance.

Prevalence of Autoimmune Diseases

• Statistics (2018 data):

  • Approximately 4 million cases in the UK

  • 1 in 5 individuals affected

  • 75% of cases occur in women.

• Autoimmune diseases rank as the 4th largest cause of disability among women.

• Rheumatoid Arthritis affects approximately 1 in 100 individuals.

Mechanism of Antigen Presentation

• Steps of Pathogen Recognition by APCs:

  1. APC recognizes a pathogen.

  2. Internalization and antigen processing.

  3. Peptide presented via MHC class II.

  4. Interaction of TCR complex with the peptide.

  5. Danger signal and co-stimulation.

  6. T cell proliferation and cytokine response.

  7. Activation of B cells and CD8 T cells to launch a full immune response.

• Normal CD4 T cell response: involves MHC-antigen and co-stimulation interactions.

Causes of Autoimmunity

• The immune system typically distinguishes between self and non-self.

• Autoimmune diseases arise when:

  • Control processes are interrupted, leading to lymphocyte suppression failure.

  • Cells/tissues are altered and mistaken for non-self.

• Factors that may trigger autoimmune processes include:

  • Bacteria, viruses, toxins, and certain drugs.

  • Genetic predisposition to autoimmune disorders.

Tolerance in the Immune System

• Tolerance: The immune system's ability to avoid attacking self-antigens.

• Breakdown of tolerance leads to autoimmune disease.

  • Tolerance mechanisms include:

    • Central tolerance (during T cell maturation in the thymus).

    • Peripheral tolerance (involving signals from normal cellular tissue).

Role of MHC Molecules

• MHC molecules are critical antigen-presenting structures.

• They partly determine immune responses to antigens and are implicated in susceptibility and development of autoimmune diseases.

Key Discoveries in Immunology

• Peter C. Doherty and Rolf M. Zinkernagel won the Nobel Prize in 1996 for discoveries related to specificity in cell-mediated immune defense.

Cytotoxic T Cells vs. B Cells

• Only viral infected cells are eliminated by cytotoxic T cells, not free virus or antigen.

• Key differences exist in responses between T cells and B cells.

T Cell Development and Selection

• T cells develop in the thymus with processes of:

  • Central Tolerance: Reactive T cells against self are eliminated; involves positive and negative selection.

  • Peripheral Tolerance: T cells in circulation depend on signals from normal tissues to survive; failure results in autoimmunity.

Figure Notes on T Cell Development

• Various stages of T cell development (e.g., precursor, immature thymocyte) illustrate gene rearrangement and selection processes.

B Cell Development and Tolerance

• Negative selection for B cells occurs in the bone marrow; cross-linking of IgM can lead to apoptosis of self-reactive B cells.

• Immature B cells undergo receptor editing or deletion if they strongly react to self-antigens.

Conclusion of Autoimmune Processes

• Chronic activation through inappropriate immune responses can lead to detrimental effects on the body, necessitating therapeutic interventions.