Immunity and the Immune System

• Immunity is the body's capacity to resist disease.
• The immune system safeguards against antigens.
• Antigens are foreign substances eliciting an immune response.
• The immune response identifies and eliminates antigens.
• Immunodeficiency disorders impair immune system function, increasing infection risk.
• Hypersensitivity reactions involve excessive immune responses, causing tissue damage.
• Autoimmune disorders result from the immune system attacking the body's own tissues.

Components of the Immune System

• The immune system comprises the thymus, bone marrow, lymph nodes, spleen, tonsils, and other lymphoid tissues.
• Leukocytes (white blood cells) are crucial, including lymphocytes (T cells, B cells, NK cells), neutrophils, macrophages, eosinophils, and basophils.
• Cytokines are signaling molecules regulating immunity, inflammation, and hematopoiesis, such as interleukins, interferons, TNF, and colony-stimulating factors.
• Antibodies (immunoglobulins) are produced by B cells to neutralize antigens.

Types of Immunity

Innate (Natural) Immunity

• Present from birth, giving immediate, non-specific protection.
• Includes physical barriers (skin, mucous membranes), chemical barriers (enzymes in tears/saliva), and cellular defenses (phagocytes, NK cells).
• Inflammation is vital for eliminating pathogens and promoting tissue repair.

Acquired (Adaptive) Immunity

• Develops over time with exposure to antigens.
• It is specific, recognizing particular antigens and forming immunological memory.
• It has two types: active and passive.

Active Immunity

• Arises when the body makes its own antibodies upon antigen exposure, through natural exposure or vaccination.
• It offers long-lasting protection due to memory cell development.

Passive Immunity

• Comes from receiving antibodies from an external source, like mother to fetus or immunoglobulin injections.
• It offers temporary protection, as the body doesn't produce its own antibodies.

Humoral Immunity

• Mediated by B cells, producing antibodies.
• Effective against extracellular pathogens like bacteria and viruses.
• B cells become plasma cells which secrete antibodies, and memory B cells, which provide long-term immunity.

Cell-Mediated Immunity

• Mediated by T cells, which directly attack infected cells or oversee the immune response.
• Effective against intracellular pathogens (viruses, fungi) and cancer cells.
• T cell types include:
  • Helper T cells (CD4+): Coordinate the immune response by activating other immune cells and releasing cytokines.
  • Cytotoxic T cells (CD8+): Directly kill infected or cancerous cells.
  • Regulatory T cells: Suppress the immune response to prevent autoimmunity.

Diagnostic Tests for Immune Disorders

• Complete Blood Count (CBC) with differential: Evaluates the number and types of white blood cells.
• Immunoglobulin levels: Measures the levels of different types of antibodies (IgG, IgM, IgA, IgE).
• T cell and B cell counts: Determines the number of T cells and B cells in the blood.
• Allergy testing: Identifies specific allergens that trigger hypersensitivity reactions.
• HIV testing: Detects the presence of HIV antibodies or viral load.
• Autoantibody testing: Detects the presence of antibodies that attack the body's own tissues (e.g., ANA, rheumatoid factor).
• Skin testing: Assesses cell-mediated immunity (e.g., TB test).

Immunodeficiency Disorders

Primary Immunodeficiency Disorders

• Genetic defects that affect immune system development or function.
• Examples include severe combined immunodeficiency (SCID), common variable immunodeficiency (CVID), and DiGeorge syndrome; often diagnosed in infancy/early childhood due to recurrent infections.

Secondary Immunodeficiency Disorders

• Result from external factors such as infections, malnutrition, medications, or other underlying conditions.
• Examples include HIV/AIDS, immunosuppressive drugs (e.g., corticosteroids, chemotherapy), and malnutrition.

HIV/AIDS

Etiology and Pathophysiology

• Caused by the human immunodeficiency virus (HIV), which attacks CD4+ T cells (helper T cells).
• HIV replicates within CD4+ T cells, leading to their destruction and a progressive decline in immune function.
• Acquired immunodeficiency syndrome (AIDS) is the advanced stage of HIV infection; characterized by a severely compromised immune system and opportunistic infections.

Transmission

• Transmitted through direct contact with infected blood, semen, vaginal fluids, or breast milk.
• Common routes of transmission include unprotected sexual intercourse, sharing needles, and mother-to-child transmission during pregnancy, childbirth, or breastfeeding.

Clinical Manifestations

• Acute HIV infection: Flu-like symptoms (fever, fatigue, rash).
• Asymptomatic chronic HIV infection: No symptoms for several years.
• Symptomatic HIV infection: Opportunistic infections, constitutional symptoms (weight loss, night sweats), and neurological complications.
• AIDS: Severe opportunistic infections, cancers (Kaposi's sarcoma, lymphoma), and wasting syndrome.

Diagnostic Tests

• HIV antibody tests (ELISA, Western blot): Detect the presence of HIV antibodies.
• HIV viral load test: Measures the amount of HIV RNA in the blood.
• CD4+ T cell count: Monitors the number of CD4+ T cells, indicating the degree of immune suppression.

Treatment

• Antiretroviral therapy (ART): Combination of drugs that suppress HIV replication, slowing disease progression and improving immune function.
• Prophylaxis against opportunistic infections: Medications to prevent infections such as Pneumocystis pneumonia (PCP), tuberculosis, and fungal infections.
• Vaccinations: Recommended to prevent vaccine-preventable illnesses, but some vaccines may be contraindicated in individuals with severe immunosuppression.

Nursing Management

• Education: Give information about HIV transmission, prevention, and treatment.
• Medication adherence: Stress the need to take ART as prescribed to maintain viral suppression.
• Monitoring: Watch for opportunistic infections and check CD4+ T cell count and viral load.
• Emotional support: Provide counseling to deal with the psychological effects of HIV/AIDS.
• Infection control: Use standard precautions to stop HIV from spreading.
• Nutrition: Encourage a balanced diet to maintain optimal immune function.

Hypersensitivity Reactions

• Exaggerated immune responses that cause tissue damage.
• Classified into four types (I-IV) based on the mechanisms involved.

Type I: Immediate Hypersensitivity

• Mediated by IgE antibodies, which bind to mast cells and basophils.
• Upon exposure to an allergen, mast cells and basophils release histamine and other mediators, causing vasodilation, increased vascular permeability, and smooth muscle contraction.
• Examples include allergic rhinitis (hay fever), asthma, anaphylaxis.

Type II: Cytotoxic Hypersensitivity

• Mediated by IgG or IgM antibodies, which bind to antigens on cell surfaces.
• Activation of complement system leads to cell lysis or phagocytosis.
• Examples include transfusion reactions, hemolytic anemia, and Goodpasture syndrome.

Type III: Immune Complex Hypersensitivity

• Mediated by IgG or IgM antibodies, which form immune complexes with antigens.
• Immune complexes deposit in tissues and activate the complement system, causing inflammation and tissue damage.
• Examples include systemic lupus erythematosus (SLE), rheumatoid arthritis, and serum sickness.

Type IV: Delayed Hypersensitivity

• Mediated by T cells, which release cytokines and cause inflammation.
• Delayed reaction, typically occurring 24-72 hours after exposure to an antigen.
• Examples include contact dermatitis (poison ivy), tuberculosis skin test, and graft rejection.

Anaphylaxis

• Severe, life-threatening systemic hypersensitivity reaction.
• Rapid onset, characterized by hypotension, bronchospasm, urticaria, and angioedema.
• Triggers include medications, insect stings, food allergies, and latex.

Nursing Management of Hypersensitivity Reactions

• Assessment: Identify the allergen and assess the patient's symptoms.
• Airway management: Ensure a patent airway and administer oxygen as needed.
• Medication administration: Administer antihistamines, corticosteroids, and epinephrine as prescribed.
• Monitoring: Monitor vital signs and respiratory status closely.
• Education: Educate the patient about allergen avoidance and emergency treatment (e.g., use of epinephrine auto-injector).

Autoimmune Disorders

• The immune system attacks the body's own tissues, leading to chronic inflammation and tissue damage.
• Etiology is multifactorial, involving genetic predisposition, environmental factors, and immune dysregulation.

Systemic Lupus Erythematosus (SLE)

• Chronic, systemic autoimmune disease that can affect multiple organs.
• Characterized by the production of autoantibodies (e.g., anti-nuclear antibodies (ANA)) that form immune complexes and cause inflammation.

Clinical Manifestations of SLE

• Fatigue, fever, joint pain, skin rashes (butterfly rash on the face), photosensitivity, and kidney involvement.

Diagnostic Tests for SLE

• ANA test, anti-dsDNA antibodies, anti-Sm antibodies, complement levels, and kidney biopsy.

Treatment for SLE

• Corticosteroids, immunosuppressants (e.g., methotrexate, azathioprine), antimalarial drugs (e.g., hydroxychloroquine), and NSAIDs.

Rheumatoid Arthritis (RA)

• Chronic, systemic autoimmune disease that primarily affects the joints.
• Characterized by inflammation of the synovial membrane, leading to joint destruction and disability.

Clinical Manifestations of RA

• Joint pain, swelling, stiffness, warmth, and deformity.

Diagnostic Tests for RA

• Rheumatoid factor (RF), anti-cyclic citrullinated peptide (anti-CCP) antibodies, ESR, and C-reactive protein (CRP).

Treatment for RA

• DMARDs (disease-modifying antirheumatic drugs) (e.g., methotrexate, sulfasalazine), NSAIDs, corticosteroids, and biologic agents (e.g., TNF inhibitors).

Nursing Management of Autoimmune Disorders

• Assessment: Assess the patient's symptoms, symptom severity, and response to treatment.
• Medication administration: Administer medications as prescribed and monitor for side effects.
• Pain management: Provide pain relief measures such as analgesics, heat or cold therapy, and physical therapy.
• Fatigue management: Encourage rest periods and energy conservation techniques.
• Education: Educate the patient about the disease, treatment options, and self-management strategies.
• Emotional support: Provide counseling and support to address psychosocial issues related to chronic illness.
• Monitor for complications: Renal, cardiac, and neurological problems.

Overview of immunity as the body's defense against disease, detailing antigens and immune responses. Explains immunodeficiency, hypersensitivity, and autoimmune disorders. Covers the system's components, including organs, leukocytes, cytokines and antibodies.