1. Based on how the immunity is acquired:
* Innate Immunity: This is the first line of defense, present at birth. It's non-specific and works against a wide range of pathogens. Examples include:
* Physical barriers (skin, mucous membranes)
* Chemical barriers (stomach acid, antimicrobial enzymes)
* Phagocytic cells (macrophages, neutrophils)
* Natural killer cells
* Adaptive Immunity: This is specific and develops throughout life through exposure to pathogens. It involves:
* Humoral Immunity: Mediated by antibodies produced by B lymphocytes (B cells)
* Cell-mediated Immunity: Mediated by T lymphocytes (T cells)
* Passive Immunity: This is temporary immunity acquired from another source. Examples include:
* Maternal Antibodies: Antibodies transferred from mother to baby via placenta or breast milk.
* Artificial Passive Immunity: Injection of pre-made antibodies (e.g., antivenom).
* Active Immunity: This is long-lasting immunity developed through the body's own immune response. Examples include:
* Natural Active Immunity: Developed through infection and recovery.
* Artificial Active Immunity: Developed through vaccination.
2. Based on the target of the immune response:
* Antigen-Specific Immunity: Targets specific antigens found on pathogens or other foreign substances. This is the primary function of adaptive immunity.
* Non-Antigen-Specific Immunity: Acts against a broad range of pathogens without recognizing specific antigens. This is the characteristic of innate immunity.
* Autoimmunity: Inappropriate immune response directed against the body's own tissues.
* Hypersensitivity: Exaggerated immune response to normally harmless substances, leading to allergies and other reactions.
3. Based on the mechanism of action:
* Humoral Immunity: Involves antibodies produced by B cells, which circulate in the blood and lymph.
* Cell-mediated Immunity: Involves T cells that directly attack infected cells or activate other immune cells.
* Complement System: A group of proteins that act in concert to kill bacteria, promote inflammation, and clear immune complexes.
* Cytokine Signaling: Communication network of proteins that regulate immune cell function and orchestrate the immune response.
4. Based on the duration of the immune response:
* Short-term Immunity: Lasts for a short period, like the protection provided by passive immunity.
* Long-term Immunity: Lasts for a longer period, like the immunity developed after vaccination or natural infection.
* Lifelong Immunity: Lasts throughout life, though the level of protection may decline with age.
* Immunodeficiency: Compromised immune response, leaving individuals more susceptible to infections.
Remember that these are just some ways to categorize immunity. There is overlap between these categories, and a single immune response can involve multiple aspects.
