Pathophysiological Concepts in Nursing Unit 4 Review: Immunity and Immune System Alterations

Basics of the Immune System

• Serves as the body's defense against infectious agents and other harmful substances
• Comprised of a complex network of cells, tissues, and organs that work together to protect the body
• Distinguishes between self and non-self substances, targeting and eliminating foreign invaders
• Responds to pathogens through innate and adaptive immune responses
  • Innate immunity is the first line of defense, providing immediate and non-specific protection
  • Adaptive immunity is a slower, more targeted response that develops after exposure to specific antigens
• Maintains a delicate balance between protecting the body and avoiding excessive inflammation or autoimmunity
• Influenced by various factors, including genetics, age, nutrition, and stress levels
• Plays a crucial role in wound healing and tissue repair processes

Types of Immunity

• Innate immunity is the body's first line of defense against pathogens
  • Non-specific and does not require prior exposure to the pathogen
  • Includes physical barriers (skin and mucous membranes), chemical barriers (enzymes and pH), and cellular components (neutrophils and macrophages)
• Adaptive immunity is a specific, targeted response to pathogens
  • Develops after exposure to a specific antigen and creates immunological memory
  • Consists of humoral immunity mediated by B lymphocytes and cell-mediated immunity mediated by T lymphocytes
• Passive immunity is the transfer of antibodies from one individual to another
  • Can occur naturally (maternal antibodies passed to fetus through placenta) or artificially (administration of preformed antibodies)
  • Provides temporary protection against specific pathogens
• Active immunity results from an individual's own immune system response to an antigen
  • Can be acquired through natural exposure to a pathogen or through vaccination
  • Provides long-lasting protection due to the development of immunological memory
• Herd immunity occurs when a significant portion of a population becomes immune to an infectious disease
  • Reduces the likelihood of disease spread, protecting individuals who cannot be vaccinated or have weakened immune systems

Key Immune System Components

• Lymphoid organs are the sites where immune cells develop, mature, and interact
  • Primary lymphoid organs include the bone marrow and thymus, where immune cells originate and mature
  • Secondary lymphoid organs include lymph nodes, spleen, and mucosa-associated lymphoid tissue (MALT), where immune cells interact with antigens and mount immune responses
• Immune cells play specific roles in the immune response
  • Leukocytes (white blood cells) include granulocytes (neutrophils, eosinophils, and basophils), lymphocytes (B cells and T cells), and monocytes/macrophages
  • Neutrophils are the most abundant leukocytes and are essential for phagocytosis and inflammation
  • Lymphocytes are responsible for specific immune responses, with B cells producing antibodies and T cells mediating cellular immunity
• Cytokines are signaling molecules that regulate immune cell communication and function
  • Include interleukins, interferons, and tumor necrosis factors
  • Modulate immune cell activation, proliferation, and differentiation
• Complement system is a group of plasma proteins that enhance the immune response
  • Promotes inflammation, opsonization (tagging pathogens for phagocytosis), and direct lysis of pathogens
• Antibodies (immunoglobulins) are proteins produced by B cells that specifically bind to antigens
  • Five main classes: IgG, IgA, IgM, IgD, and IgE, each with distinct functions and locations in the body

Normal Immune Response Process

• Antigen recognition is the first step in the immune response
  • Innate immune cells (dendritic cells and macrophages) use pattern recognition receptors (PRRs) to identify pathogen-associated molecular patterns (PAMPs)
  • Adaptive immune cells (B and T lymphocytes) use antigen-specific receptors to recognize specific epitopes on antigens
• Antigen presentation involves the processing and display of antigens by antigen-presenting cells (APCs) to lymphocytes
  • Dendritic cells, macrophages, and B cells are professional APCs that present antigens on major histocompatibility complex (MHC) molecules
  • MHC class I presents intracellular antigens to CD8+ T cells, while MHC class II presents extracellular antigens to CD4+ T cells
• Lymphocyte activation occurs when antigen-specific receptors on B and T cells bind to their corresponding antigens
  • B cells are activated by direct antigen binding and T cell help, leading to antibody production
  • T cells are activated by APCs presenting antigens on MHC molecules, leading to cytokine secretion and cell-mediated immunity
• Effector functions are the mechanisms by which activated immune cells eliminate pathogens
  • Antibodies neutralize toxins, opsonize pathogens for phagocytosis, and activate complement
  • Cytotoxic T cells directly kill infected or abnormal cells through the release of perforin and granzymes
  • Helper T cells secrete cytokines to enhance the immune response and coordinate other immune cells
• Immunological memory is the ability of the adaptive immune system to respond more quickly and effectively to previously encountered antigens
  • Memory B and T cells are long-lived cells that persist after the initial immune response
  • Upon re-exposure to the same antigen, memory cells rapidly proliferate and mount a stronger, faster immune response

Common Immune System Disorders

• Autoimmune disorders occur when the immune system mistakenly attacks the body's own tissues
  • Examples include rheumatoid arthritis, systemic lupus erythematosus (SLE), and multiple sclerosis
  • Often characterized by the presence of autoantibodies and chronic inflammation
• Immunodeficiencies are conditions in which the immune system is impaired or absent
  • Primary immunodeficiencies are genetic disorders, such as severe combined immunodeficiency (SCID) and X-linked agammaglobulinemia
  • Secondary immunodeficiencies are acquired, resulting from factors like HIV infection, malnutrition, or immunosuppressive medications
• Allergies are hypersensitivity reactions to normally harmless substances (allergens)
  • Mediated by IgE antibodies and mast cell degranulation, leading to symptoms like rhinitis, urticaria, and anaphylaxis
  • Common allergens include pollen, food proteins, and medications
• Asthma is a chronic inflammatory disorder of the airways
  • Characterized by airway hyperresponsiveness, mucus hypersecretion, and reversible airflow obstruction
  • Often triggered by allergens, irritants, or respiratory infections
• Chronic granulomatous disease (CGD) is a primary immunodeficiency affecting phagocytic cells
  • Caused by genetic defects in the NADPH oxidase enzyme complex, impairing the ability to generate reactive oxygen species
  • Leads to recurrent bacterial and fungal infections, granuloma formation, and inflammation

Immune System Alterations and Their Effects

• Immunosuppression is the intentional or unintentional suppression of the immune system
  • Can be induced by medications (corticosteroids, chemotherapy) or conditions (HIV, malnutrition)
  • Increases susceptibility to opportunistic infections and certain cancers
• Graft-versus-host disease (GVHD) is a complication of allogeneic hematopoietic stem cell transplantation
  • Occurs when donor T cells recognize recipient tissues as foreign and mount an immune response
  • Can affect multiple organs, including skin, liver, and gastrointestinal tract
• Sepsis is a life-threatening condition characterized by a dysregulated immune response to infection
  • Involves an initial hyperinflammatory phase followed by an immunosuppressive phase
  • Can lead to organ dysfunction, shock, and death if not promptly treated
• Vaccine-induced immunity is the development of protective immunity through vaccination
  • Vaccines contain antigens (attenuated or inactivated pathogens, toxoids, or recombinant proteins) that stimulate an immune response
  • Provides long-term protection against specific infectious diseases
• Immunosenescence is the gradual deterioration of the immune system with age
  • Characterized by decreased T cell diversity, impaired innate immune cell function, and reduced antibody production
  • Contributes to increased susceptibility to infections, autoimmunity, and cancer in older adults

Diagnostic Tests and Procedures

• Complete blood count (CBC) with differential evaluates the number and proportion of immune cells
  • Abnormalities may indicate infections, autoimmune disorders, or hematologic malignancies
  • Specific findings include leukocytosis (elevated white blood cell count) or leukopenia (decreased white blood cell count)
• Immunoglobulin levels (IgG, IgA, IgM) assess the humoral immune response
  • Decreased levels may suggest primary or secondary immunodeficiencies
  • Elevated levels can be seen in chronic infections, autoimmune disorders, or multiple myeloma
• Lymphocyte subset analysis quantifies the number and proportion of T cells (CD4+ and CD8+), B cells, and natural killer (NK) cells
  • Used to evaluate immune status in conditions like HIV infection or primary immunodeficiencies
  • Abnormalities may guide treatment decisions and prognosis
• Autoantibody tests detect the presence of antibodies directed against self-antigens
  • Commonly used in the diagnosis of autoimmune disorders (antinuclear antibodies for SLE, rheumatoid factor for rheumatoid arthritis)
  • Positive results should be interpreted in the context of clinical presentation and other diagnostic findings
• Skin tests assess the delayed-type hypersensitivity response to specific antigens
  • Tuberculin skin test (TST) evaluates exposure to Mycobacterium tuberculosis
  • Allergen skin tests identify specific allergies by introducing allergens intradermally and observing local reactions

Nursing Considerations and Interventions

• Infection prevention measures are crucial for patients with impaired immunity
  • Implement strict hand hygiene protocols and use personal protective equipment (PPE) when appropriate
  • Educate patients and families about avoiding exposure to potential pathogens
• Immunization status should be assessed and updated as needed
  • Ensure patients receive age-appropriate vaccinations, including annual influenza and pneumococcal vaccines
  • Be aware of contraindications and precautions for live vaccines in immunocompromised individuals
• Medication management involves monitoring for side effects and drug interactions
  • Assess for signs of immunosuppression or infection in patients receiving immunomodulatory therapies
  • Educate patients about the importance of adhering to prescribed regimens and reporting any adverse effects
• Patient education is essential for promoting self-care and early recognition of complications
  • Teach patients about their specific immune system disorder, including signs and symptoms of infection or exacerbation
  • Encourage healthy lifestyle habits, such as balanced nutrition, regular exercise, and stress management
• Psychosocial support addresses the emotional impact of chronic immune system disorders
  • Assess for signs of depression, anxiety, or social isolation
  • Provide resources for support groups, counseling services, and financial assistance programs
• Collaborative care involves working with an interdisciplinary team to manage complex immune system disorders
  • Coordinate care with specialists (immunologists, rheumatologists, infectious disease physicians) as needed
  • Communicate regularly with other healthcare providers to ensure continuity of care and optimal patient outcomes