Resources>Blog>The Immune System: Innate and Adaptive Immunity
The Immune System: Innate and Adaptive Immunity
Biointron2025-01-09Read time: 5 mins
Image credit: InformedHealth.org
The immune system is essential for protecting the body against harmful microorganisms such as bacteria, viruses, and other pathogens. It works on two primary levels: the innate (general) immune system and the adaptive (specialized) immune system. These systems are interconnected, with the innate system acting as the body's first line of defense and the adaptive system providing tailored responses to specific threats.
The Innate Immune System
The innate immune system is the body's immediate defense mechanism. It responds uniformly to any pathogen or foreign substance, often earning the label of a "non-specific" immune response. This system includes physical barriers, immune cells, and proteins, all working in harmony to prevent infection.
Physical Barriers: Skin, Mucous Membranes, and Bodily Fluids
The skin and mucous membranes serve as the first layer of defense, creating a physical barrier that prevents pathogen entry. Additional protective mechanisms include acidic environments, enzymes, and mucus, which hinder microbial growth. Bodily fluids like sweat, urine, and tears also help eliminate potential invaders, while movements such as the cilia in the lungs or bowel muscles help dislodge pathogens.
Immune Cells and Proteins: Neutralizing Invaders
When pathogens breach the physical barriers, specialized immune cells and proteins of the innate immune system take action. For example, phagocytes, or scavenger cells, engulf and digest pathogens, rendering them harmless. Natural killer cells play a critical role in identifying and destroying virus-infected or abnormal cells, including tumor cells.
Enzymes within the innate immune system contribute by marking pathogens for destruction, recruiting immune cells, and directly destroying bacterial cell walls or viral envelopes. Together, these components act swiftly to contain infections, though they cannot always eliminate pathogens entirely.
The Adaptive Immune System
When the innate immune system cannot fully neutralize a threat, the adaptive immune system is activated. This specialized system targets specific pathogens, requiring time to develop its response but offering precision and long-term memory.
T Cells: Directing the Response
T cells are produced in the bone marrow and mature in the thymus. They have several roles in adaptive immunity:
Helper T Cells activate other immune cells to start the adaptive response.
Cytotoxic T Cells detect and destroy infected or abnormal cells.
Memory T Cells remember pathogens for faster responses during subsequent infections.
T cells use specialized surface receptors to recognize pathogens. Once a match is found, they proliferate to mount an efficient immune response tailored to the specific pathogen.
B Cells and Antibodies: Neutralizing Pathogens
B cells, also produced in the bone marrow, are activated by helper T cells. Once activated, B cells multiply and differentiate into plasma cells that produce large amounts of antibodies. These antibodies bind specifically to pathogens, neutralizing them and marking them for destruction by other immune cells.
Some B cells transform into memory cells, contributing to the adaptive immune system's ability to respond quickly during future encounters with the same pathogen.
Antibodies: Multifunctional Defense
Antibodies are key players in adaptive immunity. They perform several vital functions:
Neutralizing pathogens by preventing them from binding to host cells.
Recruiting phagocytes and other immune cells to destroy marked pathogens.
Activating complementary proteins that enhance the immune response.
By providing this targeted approach, the adaptive immune system complements the innate immune system, ensuring a robust defense mechanism.
Bridging the Innate and Adaptive Immune Systems
The innate and adaptive immune systems are deeply interconnected. Antigen-presenting cells (APCs), such as macrophages and dendritic cells, bridge the gap by processing pathogens and presenting their antigens to T cells, thus activating the adaptive immune response. Cytokines and chemokines, soluble signaling molecules, further coordinate these systems to ensure an effective response against infections.
Applications in Drug Development
The advancements in immunology have profound implications for drug development. Monoclonal antibodies, derived using insights from both the innate and adaptive immune systems, are widely employed to treat conditions such as autoimmune diseases, cancers, and infectious diseases. The ability to tailor these therapies to target specific molecules ensures high efficacy and reduced off-target effects. Future developments in antibody engineering and the use of humanized models, such as transgenic mice, are expected to further enhance the therapeutic landscape, making treatments safer and more effective.
Our High-throughput Fully Human Antibody Discovery Platform integrates Cyagen’s HUGO-Ab™ mice with Biointron’s AbDrop™ microdroplet-based single B cell screening. This powerful combination accelerates the discovery and development of fully human antibodies, reducing the time from target identification to therapeutic candidate to just three months. Learn more about the service here.
References:
In brief: The innate and adaptive immune systems. (2023, August 14). Nih.gov; Institute for Quality and Efficiency in Health Care (IQWiG). https://www.ncbi.nlm.nih.gov/books/NBK279396/