Funkcje układu odpornościowego | Functions of the Immune System

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“homeostaza”, “tissue repair”: “regeneracja tkanek”, “endocrine system”: “układ dokrewny”, “nervous system”: “układ nerwowy”, “metabolic systems”: “układy metaboliczne”, “innate immunity”: “odporność wrodzona”, “adaptive immunity”: “odporność nabyta”, “physical barriers”: “bariery fizyczne”, “chemical barriers”: “bariery chemiczne”, “skin”: “skóra”, “mucous membranes”: “błony śluzowe”, “stomach acid”: “kwas solny żołądkowy”, “antimicrobial peptides”: “peptydy antydrobnoustrojowe”, “lysozymes”: “lizozymy”, “mucosal surfaces”: “powierzchnie śluzówkowe”, “ciliary movement”: “ruch rzęskowy”, “peristalsis”: “ruchy perystaltyczne”, “neutrophils”: “neutrofile”, “macrophages”: “makrofagi”, “dendritic cells”: “komórki dendrytyczne”, “natural killer cells”: “komórki NK”, “reactive oxygen species”: “reaktywne formy tlenu”, “proteolytic enzymes”: “enzymy proteolityczne”, “antigen-presenting cells”: “komórki prezentujące antygen”, “cytokines”: “cytokiny”, “inflammation”: “zapalenie”, “chemokines”: “chemokiny”, “vascular permeability”: “przepuszczalność naczyń”, “complement proteins”: “białka układu dopełniacza”, “membrane attack complex”: “kompleks atakujący błonę”, “acute-phase proteins”: “białka ostrej fazy”, “C-reactive protein”: “białko C-reaktywne”, “fibrinogen”: “fibrynogen”, “lymphocytes”: “limfocyty”, “B cells”: “limfocyty B”, “T cells”: “limfocyty T”, “plasma cells”: “komórki plazmatyczne”, “antibodies”: “przeciwciała”, “immunoglobulins”: “immunoglobuliny”, “B cell receptor”: “receptor limfocytów B”, “Helper T cells”: “limfocyty T pomocnicze”, “Cytotoxic T cells”: “limfocyty T cytotoksyczne”, “Regulatory T cells”: “limfocyty T regulatorowe”, “granzyme”: “granzyma”, “perforin”: “perforyna”, “immunological memory”: “pamięć immunologiczna”, “memory B cells”: “limfocyty B pamięci”, “memory T cells”: “limfocyty T pamięci”, “major histocompatibility complex molecules”: “cząsteczki głównego kompleksu zgodności tkankowej”, “MHC class I molecules”: “cząsteczki MHC klasy I”, “MHC class II molecules”: “cząsteczki MHC klasy II”, “vaccines”: “szczepionki”, “immunosuppressive cytokines”: “cytokiny immunosupresyjne”, “IL-10”: “interleukina 10”, “TGF-β”: “transformujący czynnik wzrostu beta”, “autoimmune diseases”: “choroby autoimmunologiczne”, “systemic lupus erythematosus”: “toczeń rumieniowaty układowy”, “rheumatoid arthritis”: “reumatoidalne zapalenie stawów”, “type 1 diabetes”: “cukrzyca typu 1”, “autoreactive T cells”: “limfocyty T autoreaktywne”, “immunosuppressants”: “leki immunosupresyjne”, “corticosteroids”: “kortykosteroidy”, “methotrexate”: “metotreksat”, “biologics”: “leki biologiczne”, “JAK inhibitors”: “inhibitory JAK”, “severe combined immunodeficiency”: “ciężki złożony niedobór odporności”, “HIV/AIDS”: “HIV/AIDS”, “antiretroviral therapy”: “terapia antyretrowirusowa”, “hypersensitivity reactions”: “reakcje nadwrażliwości”, “Type I hypersensitivity”: “nadwrażliwość typu I”, “IgE antibodies”: “przeciwciała IgE”, “allergic rhinitis”: “alergiczny nieżyt nosa”, “asthma”: “astma”, “anaphylaxis”: “anafilaksja”, “mast cell degranulation”: “degranulacja komórek tucznych”, “histamine”: “histamina”, “Type II hypersensitivity”: “nadwrażliwość typu II”, “IgG”: “przeciwciała IgG”, “IgM”: “przeciwciała IgM”, “antibody-dependent cellular cytotoxicity”: “cytotoksyczność zależna od przeciwciał”, “Type III hypersensitivity”: “nadwrażliwość typu III”, “glomerulonephritis”: “kłębuszkowe zapalenie nerek”, “Type IV hypersensitivity”: “nadwrażliwość typu IV”, “contact dermatitis”: “kontaktowe zapalenie skóry”, “CD4+ T cells”: “limfocyty T CD4+”, “apoptosis”: “apoptoza”, “neutrophil function”: “funkcja neutrofili”, “zinc”: “cynk”, “probiotics”: “probiotyki”, “prebiotics”: “prebiotyki”, “gut-associated lymphoid tissue”: “tkanka limfatyczna związana z jelitami”, “cytokine production”: “produkcja cytokin”, “T cell proliferation”: “proliferacja limfocytów T”, “cognitive-behavioral therapy”: “terapia poznawczo-behawioralna”, “vaccination”: “szczepienie”, “herd immunity”: “odporność zbiorowa”, “white blood cell counts”: “liczba białych krwinek”, “immunoglobulin levels”: “poziomy immunoglobulin”, “markers of inflammation”: “markery zapalne”, “aberrant cells”: “komórki aberracyjne”, “endocrine”: “endokrynny”, “nervous”: “nerwowy”, “line”: “wyścielają”, “respiratory”: “oddechowy”, “gastrointestinal”: “żołądkowo-jelitowy”, “urogenital”: “moczowo-płciowy”, “tracts”: “przewody”, “natural killer cells”: “komórki NK”, “perforins”: “perforyny”, “inflammatory mediators”: “mediatory zapalne”, “granzymes”: “granzymy”, “complement cascade”: “kaskada układu dopełniacza”, “major histocompatibility complex”: “główny kompleks zgodności tkankowej”, “memory cells”: “komórki pamięci”, “re-exposure”: “ponowna ekspozycja”, “inactivated pathogens”: “inaktywowane patogeny”, “attenuated”: “osłabione”, “recombinant antigens”: “rekombinowane antygeny”, “booster vaccinations”: “szczepienia przypominające”, “central tolerance”: “tolerancja centralna”, “thymus”: “grasica”, “bone marrow”: “szpik kostny”, “peripheral tolerance”: “tolerancja obwodowa”, “interleukins”: “interleukiny”, “interferons”: “interferony”, “tumor necrosis factors”: “czynniki martwicy nowotworów”, “anti-inflammatory”: “przeciwzapalny”, “pro-inflammatory”: “prozapalny”, “targeted therapies”: “terapie celowane”, “primary immunodeficiencies”: “pierwotne niedobory odporności”, “secondary immunodeficiencies”: “wtórne niedobory odporności”, “antimicrobial prophylaxis”: “profilaktyka przeciwdrobnoustrojowa”, “immunoglobulin replacement therapy”: “terapia zastępcza immunoglobulinami”, “hematopoietic stem cell transplantation”: “przeszczepienie krwiotwórczych komórek macierzystych”, “ADCC”: “cytotoksyczność komórkowa zależna od przeciwciał”, “antibody”: “przeciwciało”, “immediate antibody-mediated”: “natychmiastowa odpowiedź zależna od przeciwciał”, “immune complex-mediated”: “zależna od kompleksów immunologicznych”, “delayed-type”: “opóźniona”, “tuberculin reactions”: “reakcje 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Szacowany czas lekcji: 14 minut
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Functions of the Immune System

The immune system is a highly specialized and integrated network that serves as the primary defense mechanism of the body against pathogenic microorganisms, including bacteria, viruses, fungi, and parasites. It also plays a critical role in identifying and eliminating aberrant cells, such as those that are cancerous or infected. Beyond pathogen defense, the immune system is crucial in modulating the body’s homeostasis, tissue repair, and interaction with other physiological systems, including the endocrine, nervous, and metabolic systems.

Components of the Immune System

The immune system can be divided into two main components: innate immunity and adaptive immunity. Each component has distinct characteristics and roles that complement each other in providing a comprehensive defense mechanism.

Innate Immune System

Physical and Chemical Barriers

  • The innate immune system forms the body’s first line of defense, comprising physical barriers such as the skinand mucous membranes, as well as chemical barriers like stomach acidantimicrobial peptides, and lysozymes. These barriers prevent the entry of pathogens and create an inhospitable environment for microbial colonization. Mucosal surfaces, which line the respiratory, gastrointestinal, and urogenital tracts, produce mucus that traps pathogens, which are then cleared by mechanical actions such as ciliary movement and peristalsis.

Cellular Defenses

If pathogens breach these barriers, the innate immune response is activated. Key cells include neutrophilsmacrophagesdendritic cells, and natural killer (NK) cells

  • Neutrophilsare among the first cells to arrive at the site of infection, where they phagocytose and destroy invaders using reactive oxygen species (ROS) and proteolytic enzymes. 
  • Macrophages also engage in phagocytosis and serve as antigen-presenting cells (APCs), bridging innate and adaptive immunity by presenting pathogen-derived antigens to T cells. Additionally, macrophages produce cytokines that modulate inflammation and recruit other immune cells to the infection site. 
  • Dendritic cells capture antigens and migrate to lymphoid tissues, where they prime adaptive immune responses, acting as a crucial link between innate and adaptive immunity. NK cells target and destroy infected or transformed cells without prior sensitization through mechanisms involving perforins and granzymes, thus playing a key role in anti-viral and anti-tumor immunity.

Inflammatory Response

  • Inflammation is a hallmark of the innate immune response, characterized by redness, swelling, heat, and pain. Inflammatory mediators such as cytokines (e.g., IL-1, IL-6, TNF-α) and chemokines are released by immune cells, leading to increased vascular permeability and recruitment of additional immune cells to the site of infection. Complement proteins, which circulate in the blood, are also activated during inflammation, resulting in the formation of a membrane attack complex(MAC) that lyses pathogens. Acute-phase proteins like C-reactive protein (CRP) and fibrinogen are produced by the liver in response to pro-inflammatory cytokines, enhancing pathogen recognition and promoting phagocytosis.

Adaptive Immune System

The adaptive immune system provides a more specific and powerful response against pathogens, characterized by immunological memory, which allows the body to mount stronger and faster responses upon subsequent exposures to the same pathogen. The adaptive immune system involves complex interactions between lymphocytes and other immune cells to ensure precise antigen recognition and elimination.

Lymphocytes: The key players of adaptive immunity are B cells and T cells, which recognize specific antigens through their specialized receptors.

B Cells and Antibodies

B cells are responsible for the humoral immune response. Upon encountering an antigen, B cells undergo clonal expansion and differentiate into plasma cells that produce antibodies specific to the antigen. Antibodies (immunoglobulins) neutralize pathogens by binding to them, preventing their attachment to host cells, opsonizing them for phagocytosis, or activating the complement cascade. Memory B cells persist after an infection is cleared, providing long-term immunity by responding more rapidly and effectively upon re-exposure to the antigen. The diversity of the B cell receptor (BCR) repertoire allows for recognition of a vast array of antigens.

T Cells

T cells mediate the cell-mediated immune response and are divided into different subsets: Helper T cells (CD4+ T cells), which assist in activating B cells, cytotoxic T cells, and other immune cells through cytokine release, and Cytotoxic T cells (CD8+ T cells), which directly kill infected or cancerous cells by inducing apoptosis through granzyme and perforin pathways. Regulatory T cells (Tregs) modulate immune responses to prevent excessive activation, maintain self-tolerance, and reduce the risk of autoimmunity by releasing inhibitory cytokines like IL-10 and TGF-β.

Antigen Presentation and Activation

The adaptive immune system relies on antigen presentation for its activation. Dendritic cellsmacrophages, and B cells present antigenic peptides on major histocompatibility complex (MHC) molecules to T cells, initiating the adaptive immune response. MHC class I molecules present endogenous antigens, which are recognized by cytotoxic T cells, whereas MHC class II molecules present exogenous antigens, recognized by helper T cells. This distinction ensures that the appropriate immune response is tailored to intracellular versus extracellular pathogens.

Immune Memory and Vaccination

  • Memory Formation: A key feature of the adaptive immune system is the formation of memory cells after an initial infection. Memory B and T cells persist long-term and can rapidly expand and differentiate upon re-exposure to the same pathogen. This mechanism underlies the principle of immunity following natural infection or vaccination. Memory formation involves changes in gene expression and epigenetic modifications that enable a rapid and robust response.
  • VaccinationVaccines are designed to mimic natural infections and stimulate the formation of memory cells without causing disease. Vaccines may contain inactivated pathogenslive attenuated organismsrecombinant antigens, or mRNA, prompting the immune system to develop protective memory. The effectiveness of vaccines relies on the principle of herd immunity, which prevents the spread of infectious agents by ensuring a large proportion of the population is immune. Booster vaccinations are often required to enhance and prolong immune memory, particularly for pathogens that mutate frequently.

Regulation of the Immune System

The immune system requires tight regulation to ensure effective defense against pathogens while preventing autoimmune diseases, excessive inflammation, and tissue damage. Regulatory mechanisms are essential for balancing immune activation and immune suppression.

Tolerance Mechanisms

  • Central ToleranceCentral tolerance occurs in the thymus and bone marrow, where immature T and B cells that strongly recognize self-antigens are eliminated through negative selection. This process prevents the development of autoreactive lymphocytes, which could lead to autoimmune disorders. Thymic education also involves positive selection to ensure that T cells can adequately recognize MHC molecules.
  • Peripheral TolerancePeripheral tolerance occurs outside primary lymphoid organs and involves mechanisms that limit the activity of self-reactive immune cells that escape central tolerance. Regulatory T cells (Tregs) play a crucial role in maintaining peripheral tolerance by inhibiting the activity of potentially harmful lymphocytes through the release of immunosuppressive cytokines such as IL-10 and TGF-βAnergydeletion, and immune privilege are additional mechanisms that contribute to peripheral tolerance, ensuring that the immune system does not mount an attack against self-antigens present in peripheral tissues.

Immunoregulatory Cytokines

  • Cytokine Networks: Cytokines, such as interleukins (ILs)interferons (IFNs), and tumor necrosis factors (TNFs), coordinate immune cell communication and modulate immune responses. Pro-inflammatory cytokines (e.g., IL-1, TNF-α) enhance immune responses and inflammation, aiding in pathogen clearance, while anti-inflammatory cytokines (e.g., IL-10, TGF-β) ensure that immune responses do not become excessive and cause collateral tissue damage. The balance between pro- and anti-inflammatory cytokines is critical for resolving inflammation and restoring tissue homeostasis after an immune challenge.
  • Checkpoints and Immunoregulation: Immune checkpoints, such as CTLA-4 and PD-1, are expressed on T cells to modulate their activation and prevent chronic inflammation. Checkpoint inhibitors have emerged as therapeutic targets for cancer immunotherapy, where blocking inhibitory signals allows T cells to effectively target and eliminate cancer cells. Dysregulation of immune checkpoints can contribute to immune exhaustion or autoimmunity.

Role of the Immune System in Disease

The immune system is critical in defending against infections, but dysregulation can lead to immunodeficiency, autoimmunity, or excessive inflammation, all of which have significant clinical consequences.

Autoimmune Diseases

  • Pathophysiology: Autoimmune diseases occur when the immune system fails to discriminate between self and non-self, leading to attacks on the body’s tissues. Conditions such as systemic lupus erythematosus (SLE)rheumatoid arthritis (RA), and type 1 diabetes result from a breakdown in tolerance mechanisms, leading to chronic inflammation and tissue destruction. The presence of autoantibodies and autoreactive T cellsexacerbates tissue damage and perpetuates the disease process.
  • Treatment: Therapies for autoimmune diseases include immunosuppressants (e.g., corticosteroids, methotrexate) to dampen overall immune activity and biologics targeting specific cytokines (e.g., anti-TNF agents, IL-6 inhibitors) to reduce inflammation and immune-mediated damage. Targeted therapies, such as JAK inhibitors, offer more precise modulation of immune pathways, aiming to minimize side effects.

Immunodeficiency

  • Primary and Secondary ImmunodeficienciesPrimary immunodeficiencies are genetic disorders affecting immune components, such as severe combined immunodeficiency (SCID), characterized by defects in both B and T cells, leading to profound susceptibility to infections. Secondary immunodeficiencies are acquired, often due to HIV/AIDS, malnutrition, aging, or immunosuppressive treatments, resulting in compromised immune responses and increased susceptibility to opportunistic infections and malignancies.
  • Management: Treatment involves antimicrobial prophylaxisimmunoglobulin replacement therapy, and in some cases, hematopoietic stem cell transplantation to restore immune function. For patients with HIV/AIDS, antiretroviral therapy (ART) is essential for controlling viral replication and improving immune competence.

Hypersensitivity Reactions

Types of Hypersensitivity: Hypersensitivity reactions represent exaggerated immune responses that can cause tissue damage. These include:

TypeMechanismExamplesPathophysiology
Type I (Immediate)Mediated by IgE antibodiesAllergic rhinitis, asthma, anaphylaxisMast cell degranulation releases histamine, causing vasodilation, bronchoconstriction, and increased vascular permeability.
Type II (Antibody-Mediated)Involves IgG or IgM binding to cell surface antigensAutoimmune hemolytic anemia, Graves’ diseaseAntibody binding activates complement and mediates cell destruction through ADCC.
Type III (Immune Complex-Mediated)Caused by immune complex deposition in tissuesGlomerulonephritis, systemic lupus erythematosus (SLE), serum sicknessAccumulation of antigen-antibody complexes triggers complement activation and attracts neutrophils, leading to tissue damage.
Type IV (Delayed-Type)T cell-mediated responseContact dermatitis, tuberculin reactionsCD4+ T cells release cytokines, recruiting macrophages and leading to inflammation and tissue injury.

Maintaining Immune System Health

The immune system’s functionality can be optimized through proper nutrition, healthy lifestyle practices, and preventive healthcare measures. Maintaining a robust immune system is critical for preventing infections, reducing chronic disease risk, and supporting overall well-being.

Nutritional Considerations

  • Balanced Diet: A diet rich in vitamins A, C, D, and E, zinc, selenium, and iron is essential for immune function. Vitamin C supports neutrophil function, enhances phagocytosis, and promotes antibody production, while vitamin D modulates immune responses and reduces inflammation. Zinc is a cofactor for enzymes involved in immune cell proliferation and differentiation.
  • Probiotics and Prebiotics: Probiotics, found in fermented foods, and prebiotics, which promote beneficial gut bacteria, support immune health by modulating the gut microbiome, a key regulator of systemic immunity. The gut-associated lymphoid tissue (GALT) plays a major role in mediating immune responses, and a healthy microbiome supports mucosal barrier integrity and prevents pathogen colonization.

Physical Activity and Lifestyle

  • Exercise: Regular, moderate physical activity enhances immune surveillance by increasing immune cell circulation, including neutrophils, lymphocytes, and monocytes. Exercise stimulates anti-inflammatory cytokine release and promotes efficient immune cell exchange. Excessive intense exercise, however, can lead to immunosuppression and increased infection risk, highlighting the need for balance.
  • Sleep and Stress Management: Adequate sleep is crucial for immune regulation, as it influences cytokine production, antibody synthesis, and T cell activity. Sleep deprivation impairs adaptive immune response activation and reduces vaccine efficacy. Chronic stress elevates cortisol levels, which suppresses immune responses by inhibiting cytokine production and T cell proliferation. Techniques such as mindfulness meditation, yoga, and deep breathing mitigate stress by lowering cortisol, balancing cytokines, and enhancing parasympathetic activity. Regular relaxation practices counter chronic stress, enhancing immune resilience. Social support and cognitive-behavioral therapy (CBT) also strengthen immune health by reducing physiological stress responses.

Preventive Healthcare

  • Vaccination: Vaccination is one of the most effective strategies for boosting immune health by providing immunological memory without causing disease. Routine vaccinations help prevent infections and reduce the spread of communicable diseases. Vaccines like influenza and pneumococcal are crucial for maintaining herd immunity and reducing disease morbidity and mortality.
  • Hygiene and Infection Control: Proper hygiene practices, such as handwashing with soap and minimizing pathogen exposure through sanitation, are foundational for infection prevention. Infection control, especially in healthcare settings, is critical for protecting vulnerable populations from disease outbreaks.
  • Routine Health Screenings: Regular health screenings are essential for early detection of immune system disorders. Blood tests to measure white blood cell counts, immunoglobulin levels, and markers of inflammation, like C-reactive protein (CRP), provide insights into immune health. Early diagnosis of conditions such as autoimmune disorders or immunodeficiencies enables timely intervention, preventing complications.