Introduction to Immunity: Videos & Practice Problems

Innate immunity, also known as nonspecific immunity, provides routine protection from a broad range of pathogens and is present at birth. It includes physical barriers like skin and mucous membranes, as well as chemical defenses such as antimicrobials and acids. Adaptive immunity, or specific immunity, evolves over time and targets specific pathogens. It involves specialized cells like B and T lymphocytes and the production of antibodies. While innate immunity offers immediate defense, adaptive immunity provides a more tailored response and improves with exposure to different pathogens.

Antibodies are Y-shaped proteins that play a crucial role in adaptive immunity. They recognize and bind to specific antigens, which are foreign substances like toxins or microbes. Once bound, antibodies can neutralize the pathogen directly or mark it for destruction by other immune cells. For example, an antibody can bind to a pathogen's surface antigen, triggering an immune response that allows host immune cells to target and eliminate the pathogen. This process is essential for the body's ability to adapt and respond to specific threats over time.

Antigens are foreign substances, such as toxins or microbes, that induce an immune response. When an antigen enters the body, it is recognized by antibodies, which are Y-shaped proteins. The binding of an antibody to an antigen triggers various immune responses, such as the activation of immune cells that can target and eliminate the pathogen. This interaction is a key component of adaptive immunity, allowing the body to specifically target and remember pathogens for more effective responses in the future.

Innate immunity includes several key components that provide immediate, nonspecific defense against pathogens. These components include physical barriers like the skin and mucous membranes, which prevent pathogen entry. Chemical defenses such as antimicrobial peptides, acids, and enzymes also play a role in neutralizing pathogens. Additionally, innate immunity involves various immune cells, such as macrophages, neutrophils, and natural killer cells, which can quickly respond to and eliminate invading microbes. These components work together to provide a broad, first line of defense against infections.

B cells and T cells are essential components of adaptive immunity. B cells are responsible for producing antibodies that specifically target antigens. When a B cell encounters its specific antigen, it can differentiate into plasma cells that secrete large amounts of antibodies. T cells, on the other hand, have various roles. Helper T cells activate other immune cells, including B cells and cytotoxic T cells, which directly kill infected cells. Both B and T cells have memory cells that provide long-lasting immunity by remembering past infections and responding more rapidly upon re-exposure.