Types of immunity
Pro Research Analysisby 
Searched over 200M research papers
Types of Immunity: An Overview
Innate and Adaptive Immunity
The immune system is broadly categorized into innate and adaptive immunity. Innate immunity is the body's first line of defense and includes physical barriers, phagocytic cells, and various proteins that recognize and respond to pathogens quickly. Adaptive immunity, on the other hand, is more specialized and involves the activation of lymphocytes that target specific pathogens .
Type 1 Immunity: Cell-Mediated Defense
Key Characteristics and Functions
Type 1 immunity is primarily cell-mediated and is crucial for defending against intracellular pathogens such as viruses and certain bacteria. This type of immunity involves T-bet(+) IFN-γ-producing group 1 innate lymphoid cells (ILC1s), natural killer (NK) cells, CD8(+) cytotoxic T cells (TC1), and CD4(+) T helper 1 (TH1) cells. These cells produce cytokines like interferon-gamma (IFN-γ) and interleukin-2 (IL-2), which activate mononuclear phagocytes to engulf and destroy pathogens Annunziato2015Spellberg2001.
Role in Autoimmune Diseases
While type 1 immunity is essential for pathogen defense, it can also contribute to autoimmune diseases when dysregulated. Excessive type 1 responses can lead to organ-specific autoimmune destruction, as seen in conditions like multiple sclerosis and type 1 diabetes Annunziato2015Ashkar2000.
Type 2 Immunity: Humoral and Allergic Responses
Key Characteristics and Functions
Type 2 immunity is characterized by the production of cytokines such as IL-4, IL-5, IL-9, and IL-13. This type of immunity involves GATA-3(+) ILC2s, TC2 cells, and TH2 cells, which activate mast cells, basophils, and eosinophils. These cells are crucial for defending against extracellular parasites like helminths and for mediating allergic reactions Lloyd2018Annunziato2015Gieseck2017.
Role in Allergic Diseases and Tissue Repair
Type 2 immunity is also implicated in allergic diseases such as asthma, rhinitis, and dermatitis. Dysregulated type 2 responses can lead to chronic inflammation and pathological fibrosis in various tissues. However, type 2 cytokines also play a role in tissue repair and regeneration, highlighting their dual role in both protective and pathological processes Lloyd2018Gieseck2017Hammad2022.
Type 3 Immunity: Defense Against Extracellular Pathogens
Key Characteristics and Functions
Type 3 immunity is mediated by retinoic acid-related orphan receptor γt(+) ILC3s, TC17 cells, and TH17 cells, which produce cytokines like IL-17 and IL-22. These cytokines activate mononuclear phagocytes and recruit neutrophils, providing defense against extracellular bacteria and fungi .
Role in Autoimmune Diseases
Similar to type 1 immunity, type 3 responses can also contribute to autoimmune diseases when dysregulated. Conditions such as psoriasis and rheumatoid arthritis are associated with excessive type 3 immune responses .
Active and Passive Immunity
Active Immunity
Active immunity involves the production of antibodies and memory cells following exposure to a pathogen or through vaccination. This type of immunity provides long-lasting protection and is a key component of adaptive immunity .
Passive Immunity
Passive immunity, on the other hand, involves the transfer of antibodies from one individual to another, such as from mother to child through breast milk. This type of immunity provides immediate but short-term protection .
Conclusion
Understanding the different types of immunity—type 1, type 2, and type 3—along with the concepts of innate and adaptive immunity, is crucial for comprehending how the body defends itself against various pathogens. Each type of immunity has its unique characteristics and roles, both in protecting against infections and in contributing to autoimmune and allergic diseases.
Sources and full results
Most relevant research papers on this topic
DOI