Understanding the Basics: How Does the Immune Defence System Work?

The immune system is a complex network of cells, tissues, and organs that work together to defend the body against harmful pathogens, such as bacteria, viruses, fungi, parasites, foreign substances, and toxins. This primary function of the immune system, its defence mechanisms, is what allows us to appreciate its vital role in protecting our health and well-being. In addition to these defence mechanisms, the immune system also plays a crucial role in maintaining self-tolerance and preventing autoimmune reactions, allergies, and hypersensitivities. Immune regulation involves a delicate balance between activation and suppression of immune responses to ensure adequate defence against pathogens without causing harm to the body’s own tissues and cells. In this blog post, we will explore the basics of the immune defence system, its components, functions, and the mechanisms it employs to keep us safe and healthy.

What is the immune system?

The immune system is a complex network of cells, tissues, and organs that work together to defend the body against harmful pathogens, such as bacteria, viruses, fungi, parasites, foreign substances, toxins, and cancerous cells. Its primary function is recognizing, identifying, and eliminating these invaders while maintaining self-tolerance to prevent autoimmune reactions and ensuring immune regulation, homeostasis, and overall health and well-being.

Components of the Immune System –

Innate Immune System:

The innate immune system is the body’s first defence against pathogens and foreign substances. It includes physical barriers, such as the skin and mucous membranes, as well as cellular and molecular components, such as phagocytes (neutrophils, macrophages), natural killer (N.K.) cells, and antimicrobial proteins (complement system, cytokines) (Janeway, C.A., Travers, P., Walport, M., & Shlomchik, M.J. (2001).

Adaptive Immune System:

The adaptive immune system provides a specific and targeted response to pathogens and foreign substances the body encounters. It includes specialized cells, such as T cells (CD4+ helper T cells, CD8+ cytotoxic T cells) and B cells (plasma cells, memory B cells), as well as antibodies (immunoglobulins) produced in response to specific antigens (Abbas, A.K., Lichtman, A.H., & Pillai, S. 2018).

Functions of the Immune System –

Response and Activation: Upon recognition, the immune system mounts a coordinated response involving activating and recruiting immune cells, such as phagocytes, N.K. cells, T cells, and B cells, to eliminate invading pathogens and foreign substances (Akira, S., Uematsu, S., & Takeuchi, O. 2006).

Memory and Protection: Following exposure to specific pathogens or vaccination, the adaptive immune system forms memory cells (memory T cells, memory B cells) that provide long-lasting immunity and protection against future encounters with the same pathogens (Ahmed, R., & Gray, D. 1996).

Recognition and Identification: The immune system recognizes and identifies pathogens and foreign substances through pattern recognition receptors (PRRs) that detect specific molecular patterns (pathogen-associated molecular patterns, PAMPs) present on the surface of pathogens (Medzhitov, R., & Janeway, C.A. 2000).

Elimination and Destruction: The immune system employs various mechanisms, including phagocytosis (engulfment and destruction by phagocytes), cytotoxicity (killing of infected or abnormal cells by N.K. cells and cytotoxic T cells), and antibody-mediated neutralization and opsonization to eliminate and destroy pathogens and foreign substances (Blander, J.M., & Sander, L.E. 2012).

Mechanisms of Immune Defense

Understanding immune defence mechanisms is crucial to appreciating how our body protects itself from pathogens and maintains overall health. The immune system employs a multi-layered defence strategy involving physical and chemical barriers, cellular defence mechanisms, molecular defence systems, and adaptive immune responses to effectively combat pathogens and foreign substances.

Mucous Membranes: Mucous membranes line the respiratory, gastrointestinal, and reproductive tracts, providing a moist and protective barrier against pathogens and foreign substances. Mucous membranes produce mucus, a viscous and sticky fluid containing antimicrobial peptides, immunoglobulins (IgA), enzymes, and other antimicrobial factors that trap, immobilize, and remove pathogens and foreign substances from the mucosal surfaces, preventing their entry and colonization.

Skin: The skin acts as a robust physical barrier, preventing the entry of pathogens, microbes, and foreign substances into the body. The outermost layer of the skin, known as the stratum corneum, consists of densely packed keratinocytes that protect against environmental factors, pathogens, and mechanical injuries. The skin also contains various antimicrobial peptides (AMPs) and proteins, such as defensins and cathelicidins, which exhibit antimicrobial properties and contribute to the skin’s chemical defence mechanisms by inhibiting the growth and survival of pathogens on the skin’s surface.

Acidic Environment: The stomach produces hydrochloric acid (HCl), creating an acidic environment (pH 1.5-3.5) that inhibits the growth and survival of pathogens, bacteria, and parasites ingested with food and water. Other body fluids, such as tears, saliva, sweat, and vaginal secretions, also maintain an acidic pH and contain antimicrobial enzymes and proteins that contribute to the body’s chemical defence mechanisms by neutralizing pathogens and inhibiting their growth and colonization on mucosal surfaces.

Molecular Defense: The complement system is a group of plasma proteins that enhance the immune response by promoting inflammation, opsonization (coating pathogens for phagocytosis), and membrane attack complex (MAC) formation to lyse and destroy pathogens. The complement system can be activated through three main pathways (classical, alternative, and lectin) that converge to generate C3 convertase, leading to the cleavage of C3 and the subsequent formation of C5 convertase, which cleaves C5 and initiates the formation of the MAC to lyse pathogens.

Humoral Immunity: Humoral immunity involves B cells recognizing and binding to specific antigens, leading to their activation, proliferation, and differentiation into plasma cells that produce and secrete antibodies (immunoglobulins) targeting and neutralizing pathogens, promoting phagocytosis and complement activation, and providing long-lasting immunity through memory B cells. Antibodies bind to antigens with high specificity and affinity, exerting various effector functions, including neutralization, opsonization, complement activation, and antibody-dependent cellular cytotoxicity (ADCC), to eliminate pathogens, prevent their entry and colonization, and enhance the overall immune response.

Cellular Defense: Phagocytes, including neutrophils, macrophages, and dendritic cells, play a central role in cellular defence by recognizing, engulfing, and destroying pathogens through phagocytosis. Upon recognition, phagocytes engulf pathogens into phagosomes, which fuse with lysosomes containing digestive enzymes and antimicrobial substances to form phagolysosomes, where pathogens are degraded and destroyed, and their remnants are eliminated from the body.

Cytokines: Cytokines are signalling molecules produced by immune cells, including T cells, B cells, macrophages, and dendritic cells, to regulate and modulate the immune response, inflammation, and cell communication. Cytokines include interleukins (I.L.s), interferons (IFNs), tumour necrosis factors (TNFs), and chemokines, which exert diverse and pleiotropic effects on immune cells, tissues, and organs, contributing to immune activation, differentiation, proliferation, migration, and effector functions.

Natural Killer (NK) Cells: N.K. cells are specialized lymphocytes that recognize and kill infected or abnormal cells, such as virus-infected cells and tumour cells, by releasing cytotoxic molecules, including perforin and granzymes. These molecules induce apoptosis (programmed cell death) and lysis of target cells. NK cells play a crucial role in immune surveillance by detecting and eliminating transformed and aberrant cells before they develop into cancerous cells or contribute to spreading infections.

Immune Regulation and Tolerance

In addition to its defence mechanisms, the immune system plays a crucial role in maintaining self-tolerance and preventing autoimmune reactions, allergies, and hypersensitivities. Immune regulation involves a delicate balance between activation and suppression of immune responses to ensure adequate defence against pathogens without causing harm to the body’s tissues and cells.

Immune Dysregulation and Diseases

Immune dysregulation and dysfunction can lead to various diseases and conditions, including autoimmune diseases (rheumatoid arthritis, systemic lupus erythematosus, type 1 diabetes, multiple sclerosis, inflammatory bowel disease), allergic and hypersensitivity reactions (allergies, asthma, atopic dermatitis), immunodeficiency disorders (primary and secondary immunodeficiencies), and increased susceptibility to infections, recurrent infections, poor response to vaccinations, and impaired immune surveillance against cancerous cells.

Final Thought –

Understanding how the immune system works, including its components, functions, mechanisms of action, regulation, and diseases associated with immune dysregulation, can help us appreciate its vital role in maintaining our health and well-being. Supporting and strengthening our immune system through healthy lifestyle choices, a balanced diet, regular exercise, adequate sleep, stress management, vaccination, and medical treatments can help optimize immune function, enhance infection resilience, and promote overall health, longevity, and quality of life. The immune defense system employs a multi-layered and integrated approach involving physical and chemical barriers, cellular defence mechanisms, molecular defence systems, and adaptive immune responses to protect the body against pathogens, foreign substances, and toxins effectively. The immune system is a sophisticated and intricate network of cells, tissues, and organs that protect the body against harmful pathogens, foreign substances, and toxins while maintaining self-tolerance, immune regulation, and homeostasis. It includes innate and adaptive immune responses, immune recognition and identification mechanisms, immune activation and effector functions, and immune memory and protection mechanisms. PIROOZ Immune Defense promises to provide the necessary elements to help you regain your immune system with the best results. The products are better than any other supplements available in the market.