Immunity Mechanisms Flowchart — a labelled NEET Biology diagram with a definitions lexicon.
Immunity Mechanisms Flowchart Labelled parts: Immunity, INNATE IMMUNITY, non-specific, present from birth, Physical barriers, Skin, mucous membranes, Physiological barriers, Acid in stomach, lysozyme in tears, fever, Cellular barriers, Macrophages, neutrophils, NK cells, Cytokine barriers, Interferons, ACQUIRED IMMUNITY, specific, develops after exposure, By acquisition, Active immunity, Passive immunity, Natural: Infection, Artificial: Vaccination, Natural: Maternal antibodies, Artificial: Antiserum, By immune response, Humoral immunity, B cells and antibodies, Cell-mediated immunity, T cells. This is the non-specific, immediate line of defense against pathogens that does not require prior exposure or memory. Key components include phagocytes, complement system, and inflammation. FYI: Components like phagocytes (e.g., macrophages) and natural killer (NK) cells are crucial parts of the innate immune system, providing rapid response. These are the structural components of the body that prevent pathogen entry. Examples include the skin, epithelial linings, and cilia in the respiratory tract. FYI: The skin is the most significant physical barrier, providing a continuous, impermeable layer that prevents most microbial entry. These are specialized epithelial linings found in tracts like the respiratory, digestive, and urogenital systems. They secrete mucus, which traps pathogens and aids in clearance (mucociliary escalator). FYI: Mucous membranes are critical for defense because they contain both physical trapping mechanisms (mucus) and immune cells (lamina propria) for pathogen detection. These are physical structures that prevent the entry of pathogens into the body. Examples include the skin, mucous membranes, and cilia, which trap and remove microbes. FYI: The skin is the primary barrier, providing a tough, impermeable layer that prevents most microbial entry. An enzyme found in tears, saliva, and mucus that hydrolyzes the peptidoglycan layer of bacterial cell walls. It effectively breaks down the structural integrity of many Gram-positive bacteria. FYI: Lysozyme activity is crucial in the aqueous secretions of the eyes and respiratory tract, acting as a non-specific antimicrobial agent. These involve specialized cells and cell-surface components that restrict pathogen movement. Examples include tight junctions in epithelial cells and the complement system. FYI: Tight junctions (occludens) are found in epithelial tissues and are essential for maintaining the barrier function of organs like the gut and blood-brain barrier. Large phagocytic cells derived from monocytes that are highly effective at engulfing and digesting pathogens, cellular debris, and foreign particles. They also play a key role in antigen presentation. FYI: Macrophages are professional phagocytes and are crucial Antigen Presenting Cells (APCs) that activate T-lymphocytes. The most abundant type of white blood cell (WBC) that rapidly migrates to the site of infection. They are potent phagocytes that engulf and kill bacteria, often forming Neutrophil traps. FYI: Neutrophils are typically the first responders in acute inflammation and are characterized by their multi-lobed nucleus. Natural Killer cells are lymphocytes that provide innate immunity by recognizing and killing abnormal cells, such as virally infected cells or tumor cells. They release cytotoxic granules (perforin and granzymes). FYI: NK cells are part of the innate immune system and do not require prior sensitization or specific antigen recognition to function. These involve signaling proteins (cytokines) released by immune cells that regulate the immune response. They coordinate the activity of various immune components, such as activating phagocytes or promoting T-cell differentiation. FYI: Interleukins (ILs) and Interferons (IFNs) are major types of cytokines that act as chemical messengers to initiate and modulate immune responses. A type of cytokine released by virus-infected cells and natural killer cells. They signal neighboring cells to enter an antiviral state, making them resistant to viral replication. FYI: Interferons (IFNs) are critical components of the antiviral defense mechanism, often inducing the expression of antiviral genes in uninfected cells. Immunity that develops after exposure to a specific antigen, leading to the memory formation. This adaptive response is highly specific and long-lasting. FYI: Acquired immunity is mediated by lymphocytes (B and T cells) and is the basis of vaccination. Immunity acquired when the body is exposed to an antigen and mounts its own immune response, leading to the production of memory cells. This takes time but provides long-term protection. FYI: Vaccination is the most common way to induce active immunity, stimulating the body to produce its own antibodies. Immunity acquired by receiving pre-formed antibodies from another source (e.g., mother to child). This protection is immediate but temporary. FYI: The transfer of antibodies via the placenta (maternal antibodies) is the classic example of passive immunity. Antibodies (primarily IgG) passed from the mother to the fetus across the placenta. These provide temporary protection to the newborn against pathogens the mother has encountered. FYI: Maternal antibodies protect the neonate for several months, providing a crucial window of immunity before the baby's own immune system matures. The process of administering a vaccine (containing weakened, killed, or partial antigens) to stimulate the immune system to develop memory cells and antibodies without causing disease. This induces active immunity. FYI: Vaccines are designed to mimic natural infection safely, ensuring the immune system learns to recognize the pathogen's antigens. A serum containing pre-formed antibodies (immunoglobulins) that are administered to an individual. It provides immediate, temporary protection (passive immunity). FYI: Antiserum is used in emergency situations, such as treating tetanus or snakebite, where immediate antibody support is needed. A component of adaptive immunity mediated by B lymphocytes (plasma cells). These cells produce and secrete antibodies (immunoglobulins) that circulate in body fluids (humors) to neutralize pathogens. FYI: Humoral immunity primarily targets extracellular pathogens and toxins, neutralizing them before they can invade cells. These are lymphocytes responsible for humoral immunity. Upon activation, they differentiate into plasma cells that secrete antibodies. FYI: B cells recognize and bind to intact antigens (e.g., bacterial cell wall components). These are Y-shaped proteins (immunoglobulins) produced by plasma cells. They bind specifically to antigens, marking them for phagocytosis or neutralization. FYI: The constant region (Fc) of the antibody binds to phagocytic cells, while the variable region (Fab) binds to the antigen. This type of immunity involves T lymphocytes (T cells) that directly kill infected or abnormal cells. It is crucial for fighting intracellular pathogens. FYI: Cytotoxic T lymphocytes (CTLs) are the primary mediators of cell-mediated immunity, recognizing antigens presented on MHC Class I molecules. These are lymphocytes that recognize antigens presented by MHC molecules on the surface of other cells. They are essential for both cell-mediated and helper functions. FYI: T cells can only recognize processed peptide fragments (antigens), not the intact antigen itself.