In-Depth Notes on Immunology

Introduction to Immune System

• Overview of immune interactions and types of cells involved.
• Importance of understanding immune responses and concepts of immunology.

Immune System Basics

• Cells that interact with invaders can be both visible and invisible at times.
• Not all bacteria are harmful; some are beneficial and do not pose a threat.
• Intracellular pathogens like leprosy and tuberculosis can pose challenges for immune response.

NK Cells and Immune Response

• Natural Killer (NK) cells play a role in recognizing abnormal cells, including cancerous cells.
• Allergic responses occur when the immune system overreacts to non-threatening substances.
• Autoimmune disorders arise when the immune system mistakenly targets the body’s own cells.

Types of Immunity

• Distinction between humoral and cell-mediated immunity.
• Humoral Immunity: Involves B cells and antibodies. Does not require direct cell contact.
• Cell-Mediated Immunity: Involves T cells and requires direct contact with infected cells.

T Cells and B Cells

• The T cell activation process includes multiple phases: selection, clonal expansion, and differentiation.
• Subtypes of T cells:
• Cytotoxic T Cells: Destroy infected or cancerous cells.
• Helper T Cells (CD4): Help stimulate immune responses and activate B cells.
• Regulatory T Cells: Turn down immune responses once an infection is cleared.
• Memory T Cells: Remain for quicker response upon re-exposure to the same antigen.
• B cells also respond to specific antigens and can produce antibodies.

MHC Molecules

• MHC (Major Histocompatibility Complex): Critical for antigen presentation to T cells.
• MHC class I and II are key players in recognizing infected or harmful cells.
• Antigen presenting cells (APCs) like dendritic cells use MHC II to present antigens to T helper cells, initiating an immune response.

Autoimmunity and Immune Tolerance

• The immune system must differentiate between self and non-self to prevent autoimmune responses.
• Failure to recognize self can lead to diseases where the body attacks its own tissues.

Immune Memory and Vaccines

• Memory cells are crucial for long-lasting immunity.
• Different vaccines stimulate immune responses to help defend against viruses and bacteria.
• Active vs. passive immunity discussed:
• Active Immunity: Developed through natural exposure or vaccination.
• Passive Immunity: Immediate protection via received antibodies (e.g., from mother’s milk).

Antibody Structure and Function

• Antibodies have variable regions for specificity against antigens and constant regions for structural function.
• Major classes of antibodies include IgG, IgM, IgA, IgD, and IgE.
• IgG: Most abundant, can cross the placenta, and remains in circulation long-term.
• IgM: Largest size, first produced during an immune response.
• IgA: Found on mucosal surfaces, secreted into bodily fluids.
• IgE: Involved in allergic responses.

Conclusion

• Understanding the intricate interactions between various immune components can provide insights into health and disease.
• Importance of continuous research in immunology for developing effective treatments and vaccines.