Introduction to Immunology

Introduction to Immunology

• Immunology is the study of immune responses, cellular and molecular events following exposure to microbes and foreign molecules.
• The immune system's primary function is to prevent or eradicate infections.
• Immunity encompasses resistance to pathogens and reactions to non-infectious substances (e.g., harmless environmental molecules, tumors).
• The Latin term "immunitas" signifies a state of protection, drawing roots from ancient Roman law.

Learning Outcomes

• Understanding basic concepts of the immune system, its functions, and components.
• Identifying differences between innate and adaptive immunity.
• Describing the roles of immune cells (e.g., T cells, B cells, phagocytes) in pathogen defense.
• Explaining antigen recognition and immune response generation.
• Discussing the importance of immunological memory for long-term pathogen protection.
• Exploring the relationship between immunity, disease, and conditions like autoimmune disorders and immunodeficiencies.
• Analyzing the impact of immunization on public health and disease prevention.

Innate Immunity

• First line of defense against microbial invasion, acting rapidly.
• Relies on epithelial barriers (skin, mucosal tissues), cells, and natural antibiotics present in the epithelia to prevent microbial entry.
• If microbes breach these barriers, innate immunity uses phagocytes (engulfing microbes) and innate lymphoid cells (ILCs), complement system, etc.

Adaptive Immunity

• Takes time to develop after initial encounter with pathogens.
• Involves lymphocytes (e.g., B and T cells) with diverse, variable receptors recognizing a wide array of molecules (including microbial and non-infectious substances).
• Adaptive immunity mounts faster, larger, and more effective responses upon repeated exposure to pathogens (immunological memory).

Cells of the Immune System

• Lymphocytes: Adaptive immune cells that recognize antigens and differentiate into cells executing defense functions.
• Antigen-presenting cells: Capture antigens and display them to lymphocytes.
• Effector cells: Leukocytes (white blood cells) eliminating microbes, often including lymphocytes but also other leukocytes.

Active vs. Passive Immunity

• Active immunity results from exposure to antigens via infection or vaccination, where the body develops resistance to the pathogen.
• Passive immunity involves transferring antibodies or lymphocytes from an immunized individual to a recipient, offering temporary protection.

Tissues of the Immune System

• Lymphoid tissues (e.g., spleen, lymph nodes).
• Generative lymphoid organs (e.g., bone marrow, thymus), which foster the maturation of lymphocytes.

Humoral immunity

• Mediated by proteins (antibodies) produced by B lymphocytes.
• Targets extracellular pathogens, enhancing uptake by phagocytes.

Cell-Mediated Immunity

• Mediated by T lymphocytes, targeting intracellular microbes (e.g., viruses).

Memory

• Adaptive immunity mounts faster, larger, and more effective responses to repeated exposures to the same antigen. This phenomenon is called immunological memory, crucial for protection against reinfection.

Learning Outcomes (Summary)

• Learning objectives for understanding the immune system and its workings are defined, enabling deeper comprehension of its complexity.