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📚 UNIT IV: IMMUNITY, HYPERSENSITIVITY & IMMUNIZATION

Complete Nursing Exam-Ready Notes

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1. INTRODUCTION

• The human body is constantly exposed to harmful microorganisms (bacteria, viruses, fungi, parasites).
• The body has a defense system called the immune system to fight these threats.
• This unit covers how immunity works, what happens when it overreacts (hypersensitivity), and how we use vaccines to protect people.

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2. DEFINITION

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3. TYPES / CLASSIFICATION OF IMMUNITY

A. Basic Classification

IMMUNITY
├── INNATE (Natural / Non-Specific)
│   ├── Present from birth
│   ├── No memory
│   └── First line of defense
└── ADAPTIVE (Acquired / Specific)
    ├── Develops after exposure
    ├── Has MEMORY
    └── Specific to each antigen

B. Innate Immunity — Details

C. Adaptive Immunity — Details

ADAPTIVE IMMUNITY
├── HUMORAL (B-cell mediated)
│   ├── B lymphocytes → plasma cells → ANTIBODIES
│   ├── Fights extracellular pathogens (bacteria, viruses in blood)
│   └── Example: antibodies against Tetanus toxin
└── CELL-MEDIATED (T-cell mediated)
    ├── T lymphocytes (T-helper, T-cytotoxic)
    ├── Fights intracellular pathogens (viruses, TB, fungi)
    └── Example: killing of virus-infected cells by CD8+ T cells

D. Classification by How Immunity Is Acquired

ACQUIRED IMMUNITY
├── ACTIVE (host makes own antibodies)
│   ├── Natural Active → infection/disease (e.g., chicken pox)
│   └── Artificial Active → VACCINES (e.g., MMR vaccine)
└── PASSIVE (ready-made antibodies given)
    ├── Natural Passive → maternal antibodies via placenta/breast milk
    └── Artificial Passive → antiserum/immunoglobulins (e.g., anti-rabies serum)

Mnemonic: NAPA — Natural Active, Passive Active → think "NAPA" for the four types

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4. ANTIGEN AND ANTIBODY REACTION

What is an Antigen?

• A substance (usually protein or polysaccharide) that the immune system recognizes as foreign
• Has special sites called epitopes (antigenic determinants) — these are the parts the antibody binds to
• Types:
  • T-dependent antigen → needs T-helper cells to stimulate antibody production (most proteins)
  • T-independent antigen → stimulates B cells directly (polysaccharides)

What is an Antibody (Immunoglobulin)?

• A Y-shaped glycoprotein made by plasma cells (activated B cells)
• Specifically binds to the antigen that triggered its production

Antigen-Antibody Reaction (Immunological Reaction)

Antigen enters body
      ↓
Recognized by B cells (with help from T-helper cells)
      ↓
B cells → Plasma cells → Antibodies produced
      ↓
Antibody binds to specific antigen (lock-and-key)
      ↓
Results in:
  ├── Neutralization (toxin/virus rendered harmless)
  ├── Opsonization (antigen coated for phagocytosis)
  ├── Complement activation (bacterial lysis)
  ├── Agglutination (clumping of antigens)
  └── Precipitation (soluble antigen made insoluble)

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5. IMMUNOGLOBULINS: STRUCTURE, TYPES & PROPERTIES

Structure of an Antibody (IgG as model)

         Fab (Antigen-binding)    Fab
              ┌────────┐        ┌────────┐
              │  VH+VL │        │  VH+VL │    ← Variable regions (bind antigen)
              └────┬───┘        └────┬───┘
                   │                │
              ─────┴────────────────┴─────
              │     HINGE REGION          │    ← Flexible
              │         CH2              │
              │         CH3              │    ← Fc region (complement, receptor binding)
              └──────────────────────────┘

• 2 Heavy chains (H) + 2 Light chains (L) linked by disulfide bonds
• Each chain has a Variable region (V) — binds antigen (unique per antibody)
• Each chain has a Constant region (C) — determines Ig class and effector function
• Fab fragment = antigen-binding fragment (contains variable regions)
• Fc fragment = crystallizable fragment (binds complement, macrophage receptors)
• Paratope = part of antibody that binds to epitope

Five Classes of Immunoglobulins

Mnemonic: GAMED — IgG, IgA, IgM, IgE, IgD (in order of serum concentration)

Properties Summary Table

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6. HYPERSENSITIVITY REACTIONS

Definition

• An exaggerated or inappropriate immune response to an antigen (allergen) that causes tissue damage
• Classified by Gell and Coombs (1963) into 4 types

Gell & Coombs Classification

HYPERSENSITIVITY
├── Type I  → Immediate / Anaphylactic (IgE-mediated)
├── Type II → Cytotoxic (IgG/IgM-mediated, cell destruction)
├── Type III → Immune Complex (IgG-mediated, complex deposition)
└── Type IV → Delayed / Cell-mediated (T-cell mediated, NO antibody)

Mnemonic: ACID — Anaphylactic, Cytotoxic, Immune-complex, Delayed

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TYPE I — Immediate Hypersensitivity (Anaphylactic)

First exposure to allergen (e.g., peanut, penicillin, pollen)
      ↓
B cells stimulated → IgE antibodies produced
      ↓
IgE binds to surface of MAST CELLS and BASOPHILS (sensitization)
      ↓
Second exposure to same allergen
      ↓
Allergen cross-links IgE on mast cells
      ↓
DEGRANULATION → release of:
  ├── Histamine → vasodilation, bronchoconstriction, itching
  ├── Leukotrienes → prolonged bronchoconstriction
  ├── Prostaglandins → inflammation
  └── Tryptase (marker of anaphylaxis)
      ↓
Clinical effects: urticaria, angioedema, bronchospasm, anaphylaxis

• Anaphylaxis (penicillin, bee sting)
• Bronchial asthma
• Allergic rhinitis (hay fever)
• Urticaria (hives)
• Food allergy (peanuts, shellfish)

A 22-year-old nursing student receives IV penicillin and within 10 minutes develops rash, swelling of throat, low BP, and difficulty breathing → Anaphylactic shock = Type I hypersensitivity. Treatment: Adrenaline (epinephrine) 0.5 mg IM immediately.

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TYPE II — Cytotoxic Hypersensitivity

Antibody (IgG/IgM) binds to antigen on HOST CELL SURFACE
      ↓
Complement activated → cell LYSIS (MAC attack)
OR
Phagocytosis of opsonized cells
OR
ADCC (Antibody Dependent Cell-mediated Cytotoxicity)
      ↓
HOST CELLS DESTROYED

• ABO transfusion reactions (wrong blood group given)
• Hemolytic disease of newborn (Rh incompatibility — Rh−ve mother, Rh+ve baby)
• Autoimmune hemolytic anemia
• Goodpasture syndrome (antibodies to glomerular basement membrane)
• Myasthenia gravis (antibodies against acetylcholine receptors)
• Graves' disease (antibodies stimulate TSH receptors → hyperthyroidism)

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TYPE III — Immune Complex Hypersensitivity

Antigen (soluble) + Antibody → IMMUNE COMPLEX formed
      ↓
Immune complexes DEPOSIT in vessel walls, glomeruli, joints
      ↓
Complement activated
      ↓
Neutrophils attracted → release lysosomal enzymes
      ↓
TISSUE INFLAMMATION and DAMAGE

• Serum sickness (after horse antiserum — old anti-tetanus)
• Post-streptococcal glomerulonephritis
• Systemic Lupus Erythematosus (SLE)
• Rheumatoid arthritis
• Arthus reaction (local immune complex reaction — repeat injection)
• Farmer's lung (inhaled mold antigens)

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TYPE IV — Delayed-Type Hypersensitivity (Cell-Mediated)

First exposure to antigen → T cells sensitized (memory T cells formed)
      ↓
Second exposure (24–72 hrs later)
      ↓
Memory T cells recognize antigen via APC (dendritic cells/macrophages)
      ↓
T cells activated → release CYTOKINES (IFN-γ, TNF, IL-2)
      ↓
Macrophages activated → release inflammatory mediators
      ↓
TISSUE DESTRUCTION (granuloma formation)

• Tuberculin (Mantoux) test ← most important exam example
• Contact dermatitis (nickel, latex, poison ivy)
• Graft rejection (transplant rejection)
• Granulomatous diseases (TB, leprosy, sarcoidosis)

A nurse reads a Mantoux test 72 hours after injection. She finds induration [hardness] of 15 mm → Positive → suggests TB infection = Type IV hypersensitivity

Comparison Table of All 4 Types

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7. SEROLOGICAL TESTS (Antigen-Antibody Tests)

Serology [sero = serum] = laboratory tests that detect antibodies or antigens in blood serum

Classification of Serological Tests

A. Precipitation Tests

• Antigen + Antibody → insoluble precipitate forms
• Examples:
  • Immunodiffusion (Ouchterlony test) — antigens/antibodies diffuse in gel; precipitation line forms where they meet
  • VDRL test (Venereal Disease Research Laboratory) — for syphilis screening; flocculation [clumping] reaction
  • RPR test (Rapid Plasma Reagin) — syphilis
  • C-reactive protein (CRP) test — detects inflammation

B. Agglutination Tests

• Antigen (cell surface) + Antibody → visible clumping
• Examples:
  • Widal test — for typhoid fever (detects antibodies against Salmonella typhi)
  • ABO blood grouping — agglutination of RBCs
  • Coombs test (DCT/ICT) — hemolytic disease of newborn, autoimmune hemolytic anemia
  • ASO test (Anti-Streptolysin O) — detects recent streptococcal infection
  • RA Factor (Rheumatoid Factor) test — for rheumatoid arthritis

C. Complement Fixation Tests

• If antigen + antibody present → complement is "used up" (fixed) → indicator system remains intact (no lysis)
• Examples:
  • Wassermann test — syphilis (historical)
  • CFT for viral antibodies — measles, mumps

D. Neutralization Tests

• Antibody neutralizes the biological activity of a toxin or virus
• Examples:
  • ASO titre — neutralization of streptolysin O
  • Virus neutralization tests — check immunity to specific viruses

E. Immunofluorescence Tests

• Antibodies labeled with fluorescent dye → seen under fluorescence microscope
• Examples:
  • IFAT (Indirect Fluorescent Antibody Test)
  • ANA test (Anti-Nuclear Antibody) — for SLE
  • TPHA test — for syphilis confirmation

F. Enzyme-Linked Tests (ELISA)

• ELISA (Enzyme-Linked ImmunoSorbent Assay)
• Most common and important modern test
• Detects antibodies (IgG, IgM) or antigens
• Used for:
  • HIV screening (ELISA for anti-HIV antibodies)
  • Hepatitis B & C
  • TORCH infections in pregnancy
  • COVID-19 antibody tests

G. Radioimmunoassay (RIA)

• Uses radioactively labeled antigen or antibody
• Very sensitive but requires radioactive material
• Used for: hormone levels (insulin, TSH), HBsAg (Hepatitis B surface antigen)

H. Western Blot

• Confirmatory test for HIV (after ELISA screening)
• Separates viral proteins by electrophoresis → detected by antibodies
• Gold standard for HIV confirmation

Important Serological Tests Summary Table

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8. VACCINES: TYPES, CLASSIFICATION, STORAGE & COLD CHAIN

Definition

• A vaccine is a biological preparation that provides active acquired immunity to a specific disease
• It contains antigens (weakened/killed/toxoid/subunit) that stimulate an immune response without causing disease

Types / Classification of Vaccines

1. Live Attenuated [weakened] Vaccines

• Contain weakened but living microorganisms
• Give strong, long-lasting immunity (similar to natural infection)
• Usually 1–2 doses sufficient
• Contraindicated in immunocompromised patients (HIV, on steroids)

2. Killed (Inactivated) Vaccines

• Contain dead microorganisms — cannot cause disease
• Safer, more stable
• Require multiple doses + boosters (weaker immunity)
• Safe in immunocompromised patients

3. Toxoid Vaccines

• Made from inactivated bacterial toxins (the poison, not the bacteria)
• Stimulate antibodies against toxin only
• Very stable

4. Subunit / Recombinant Vaccines

• Contain only specific parts (proteins) of the pathogen
• Very safe, no risk of infection
• Hepatitis B vaccine (HBsAg protein) — recombinant DNA technology
• Pertussis acellular (DTaP) — pertussis proteins only
• HPV vaccine (Gardasil, Cervarix) — virus-like particles
• Pneumococcal vaccine (PCV)
• Meningococcal vaccine

5. Conjugate Vaccines

• Polysaccharide antigen conjugated (joined) to a protein carrier
• Makes polysaccharide antigens work in infants (T-cell dependent response)
• Examples:
  • Hib vaccine (Haemophilus influenzae type b)
  • PCV (Pneumococcal Conjugate Vaccine)
  • MenACWY (Meningococcal conjugate vaccine)

6. mRNA Vaccines (Newer type)

• Deliver instructions (mRNA) for cells to make viral protein → immune response
• Example: COVID-19 vaccines (Pfizer-BioNTech, Moderna)
• No DNA alteration; mRNA quickly degraded

7. Combination Vaccines

• Multiple vaccines in one injection
• Reduces number of injections, increases compliance

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Vaccine Storage and Handling

Principles

• Vaccines are biological products — destroyed by heat, freezing (some), and light
• Must be stored at correct temperature throughout supply chain

Storage Temperatures

⚠️ Key exam point: Vaccines most sensitive to freezing: DPT, TT, Hepatitis B, IPV, Pentavalent
⚠️ Vaccines most sensitive to heat: OPV, BCG, Measles, MMR

Reconstituted Vaccines (mixed before use)

• BCG, Measles, MMR must be used within 4–6 hours after reconstitution [mixing with diluent]
• Discard unused reconstituted vaccine at end of session

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Cold Chain

Definition

• Cold chain = the system of transporting and storing vaccines at the correct temperature from manufacturer to patient

Importance

• Maintains potency (effectiveness) of vaccines
• Prevents vaccine wastage
• Ensures immunization programs succeed

Cold Chain Equipment

VACCINE MANUFACTURER (−25°C to −15°C or +2 to +8°C)
      ↓
PRIMARY VACCINE STORE (National level) — Deep freezers + ILR
      ↓
REGIONAL / STATE VACCINE STORE — Deep freezers + ILR
      ↓
DISTRICT VACCINE STORE — ILR (Ice-Lined Refrigerator) + Deep freezers
      ↓
PHC (Primary Health Center) — ILR + Deep freezers
      ↓
SUBCENTRE / SESSION SITE — Vaccine carrier + cold packs
      ↓
PATIENT / COMMUNITY

• ILR = Ice-Lined Refrigerator (insulated box, runs on electricity, stores +2 to +8°C)
• Deep Freezer = stores at −15°C to −25°C (for OPV, BCG)
• Vaccine carrier = insulated box with frozen ice packs — for transport to field
• Cold box = large insulated box for transport between stores
• Cold packs / Ice packs = keep vaccines cold in carrier

Cold Chain Monitoring Tools

VVM Reading (Exam Important)

VVM (inner square inside outer circle)
├── Inner square LIGHTER than outer circle → USABLE ✅
└── Inner square SAME or DARKER than outer circle → DISCARD ❌

Nursing Responsibilities in Cold Chain

• Check temperature daily (2 times/day: morning and evening) — record in temperature log
• Never store food, blood, or other items in vaccine fridge
• Never keep vaccines in door of refrigerator (temperature fluctuates)
• Place ice packs at bottom of vaccine carrier before use
• Check VVM before giving each vaccine
• Report cold chain equipment failures immediately
• Store vaccines according to FIFO (First In, First Out) principle
• Keep extra ice packs in freezer always

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9. IMMUNIZATION FOR VARIOUS DISEASES — NATIONAL IMMUNIZATION SCHEDULE (India)

Universal Immunization Programme (UIP)

• Started in India in 1985 (expanded from EPI started 1978)
• Mission Indradhanush launched 2014 — aimed to increase coverage to 90%+ children
• Target: Pregnant women + children 0–5 years

Immunization Schedule (India — Current UIP)

Vaccines for Pregnant Women

Protection conferred: Prevents neonatal tetanus (tetanus in newborn) and maternal tetanus

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Other Important Vaccines (Optional/Special Situations)

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10. NURSING CARE IN IMMUNIZATION

Pre-vaccination Nursing Responsibilities

• Take detailed history: previous vaccinations, allergies, current illness
• Contraindications to check:
  • Acute febrile illness → postpone vaccine
  • Anaphylaxis to previous dose → contraindicated
  • Live vaccines in immunocompromised patients
  • Encephalopathy within 7 days of DPT → no more DPT
• Inform parents about the vaccine, disease it prevents, and possible side effects (consent)
• Check VVM on each vaccine vial
• Check expiry date
• Prepare correct dose and reconstitute if needed
• Check cold chain maintenance

During Vaccination

• Use correct route (IM, SC, intradermal, oral)
• Use correct site as per age
• Use proper injection technique (no air bubbles for injections)
• Observe strict aseptic technique
• Dispose of needles safely (no recapping — sharps container)
• Reconstituted vaccine: shake well before use

Post-vaccination Nursing Responsibilities

• Observe patient for 30 minutes for anaphylaxis (especially after first dose)
• Anaphylaxis kit ready: adrenaline, antihistamine, corticosteroids, IV fluids
• Document: vaccine name, dose, batch number, expiry, site, date
• Inform parents about normal post-vaccination reactions
• Advice for common side effects:
  • Fever → paracetamol, tepid sponging
  • Local swelling/redness → cold compress, reassurance
  • BCG ulcer/scar → normal, no treatment needed
  • OPV: sore mouth → very rare; reassure

AEFI (Adverse Events Following Immunization)

• Any untoward medical event that follows immunization
• Types:
  1. Vaccine-related (e.g., VAPP — vaccine-associated paralytic polio from OPV)
  2. Injection-related (abscess, nerve damage)
  3. Immunization error (wrong dose, wrong route)
  4. Coincidental (not caused by vaccine)
• Must be reported to health authorities within 24 hours for serious AEFI

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11. SIGNS & SYMPTOMS — ANAPHYLAXIS (most important acute immune emergency)

Anaphylaxis = severe, life-threatening Type I hypersensitivity reaction

Mnemonic: "ABCDEF" for Anaphylaxis features

• Airway obstruction (throat swelling, stridor)
• Breathing difficulty (bronchospasm, wheeze)
• Cardiovascular collapse (hypotension, tachycardia)
• Dermal signs (urticaria, angioedema, flushing, itching)
• Excretion (nausea, vomiting, diarrhea)
• Feeling of doom (anxiety, confusion, loss of consciousness)

Anaphylaxis Management (Nursing Emergency)

RECOGNIZE: Symptoms within minutes of exposure
      ↓
CALL FOR HELP / CODE BLUE
      ↓
LAY PATIENT FLAT — raise legs (unless breathing difficulty → semi-recumbent)
      ↓
ADRENALINE (EPINEPHRINE): 0.5 mg IM (1:1000) in outer thigh — FIRST DRUG
      ↓
O₂ therapy (high flow, 10–15 L/min via mask)
      ↓
IV access — normal saline bolus (500 ml–1 L)
      ↓
ANTIHISTAMINE: Chlorphenamine 10 mg IV/IM
      ↓
HYDROCORTISONE: 200 mg IV (prevents biphasic reaction)
      ↓
MONITOR: BP, pulse, SpO₂ every 5 min
      ↓
OBSERVE minimum 6 hours (risk of biphasic reaction — second wave)

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12. DIAGNOSIS / INVESTIGATIONS FOR IMMUNE DISORDERS

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13. COMPLICATIONS

Complications of Immune Disorders

Complications of Vaccines

Complications of Cold Chain Failure

• Vaccine rendered ineffective (loss of potency)
• Vaccine-preventable disease outbreaks
• False sense of security in immunized population

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14. PREVENTION

• Maintain cold chain rigorously
• Educate communities about immunization benefits
• Ensure complete immunization schedule is followed (full doses, correct timing)
• Monitor for AEFI and report
• Conduct immunization camps in remote areas (Mission Indradhanush)
• Administer vaccines by trained healthcare personnel only
• Maintain herd immunity [when enough population is immune, disease cannot spread]

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15. QUICK REVISION POINTS ⚡

• Innate = non-specific, fast, no memory | Adaptive = specific, slower, has memory
• Active immunity = makes own antibodies (long lasting) | Passive = ready-made antibodies (short lasting)
• IgG = most abundant, crosses placenta | IgA = secretions/mucosa | IgM = first in primary response | IgE = allergy/anaphylaxis
• Type I = IgE, mast cells, immediate → anaphylaxis, asthma, urticaria
• Type II = IgG/IgM, cell destruction → ABO mismatch, hemolytic disease of newborn
• Type III = immune complexes → SLE, serum sickness, post-strep GN
• Type IV = T cells, 48–72 hrs → Mantoux test, contact dermatitis, graft rejection
• VDRL = syphilis | Widal = typhoid | ELISA = HIV, Hep B | Western Blot = HIV confirmation
• VVM inner square lighter than outer = vaccine usable ✅ | Same/darker = discard ❌
• DPT, TT, HepB = freeze-sensitive | OPV, BCG = heat-sensitive
• First drug in anaphylaxis = ADRENALINE (Epinephrine) 0.5 mg IM
• BCG given at birth (0–24 hrs) | OPV birth dose also at birth
• Pentavalent = 5 antigens in 1 vaccine: DPT + HepB + Hib
• Observe 30 minutes post-vaccination for anaphylaxis

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16. MICROBIOLOGY — RELEVANT POINTS

Immunological Aspects of Microbiology

• Typhoid: Widal test (H & O agglutinins ≥ 1:160 = significant)
• Syphilis: VDRL (screening) → TPHA or FTA-ABS (confirmation)
• HIV: ELISA (screening) → Western blot (confirmation)
• Hepatitis B: HBsAg (surface antigen) = active infection; Anti-HBs = immunity

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17. PHARMACOLOGY — RELEVANT DRUGS

Drugs Used in Anaphylaxis

Drugs Used in Hypersensitivity (Allergy)

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18. CLINICAL EXAMPLES

Case 1: Anaphylaxis

A 30-year-old woman receives IV amoxicillin for UTI. Within 5 minutes she develops generalized urticaria, throat tightness, wheezing, and BP drops to 70/40 mmHg.
Diagnosis: Anaphylaxis — Type I hypersensitivity to penicillin
Immediate nursing action: Stop drug → Call help → Lay flat → Adrenaline 0.5 mg IM → O₂ → IV fluids

Case 2: Mantoux (Tuberculin) Test

A 20-year-old nurse undergoes a Mantoux test. At 72 hours, she has induration [raised hardness] of 18 mm.
Interpretation: Positive (≥10 mm in healthcare workers = significant)
Type: Type IV (Delayed) Hypersensitivity
Next step: Chest X-ray + sputum AFB smear to rule out active TB

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📝 EXAMINATION QUESTIONS

LONG QUESTIONS (10–15 marks each)

1. Classify immunity. Describe innate and adaptive immunity in detail with differences.
2. Describe the structure and classes of immunoglobulins. Add a note on their properties and functions.
3. Classify and explain hypersensitivity reactions with pathophysiology, clinical examples, and nursing management.
4. Describe the cold chain system in immunization. What are cold chain equipment, monitoring tools, and nursing responsibilities in maintaining cold chain?
5. Write the national immunization schedule for children under 5 years. Add a note on vaccines for pregnant women and AEFI.

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SHORT QUESTIONS (5 marks each)

1. Write a note on Type I (anaphylactic) hypersensitivity — mechanism and management.
2. Differentiate between active and passive immunity with examples.
3. Explain the Gell and Coombs classification of hypersensitivity reactions.
4. What is the Vaccine Vial Monitor (VVM)? How is it used?
5. Write a short note on serological tests used in clinical practice.

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VERY SHORT QUESTIONS (2 marks each)

1. Define antigen and antibody.
2. What is an epitope?
3. Which immunoglobulin crosses the placenta?
4. Name the immunoglobulin involved in allergic reactions.
5. What is the first drug given in anaphylaxis?
6. What is herd immunity?
7. Define cold chain.
8. What is AEFI? Give one example.
9. State two freeze-sensitive vaccines.
10. What is the route and dose of BCG vaccine?

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MULTIPLE CHOICE QUESTIONS (MCQs)

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ANSWER KEY

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📄 FINAL 1-PAGE QUICK REVISION SUMMARY

╔══════════════════════════════════════════════════════════════════════════╗
║          IMMUNITY, HYPERSENSITIVITY & IMMUNIZATION — QUICK REVISION      ║
╠══════════════════════════════════════════════════════════════════════════╣
║ IMMUNITY                                                                 ║
║ Innate = fast, non-specific, no memory (skin, phagocytes, NK cells)      ║
║ Adaptive = slow, specific, has memory (B cells→antibodies; T cells)      ║
║ Active (own antibody, long-lasting) vs Passive (ready-made, short)       ║
╠══════════════════════════════════════════════════════════════════════════╣
║ IMMUNOGLOBULINS (GAMED)                                                  ║
║ IgG = most abundant, crosses placenta                                    ║
║ IgA = secretions (saliva, milk, tears)                                   ║
║ IgM = first in primary response, pentamer                                ║
║ IgE = allergy/anaphylaxis (binds mast cells)                             ║
║ IgD = B-cell surface receptor                                            ║
╠══════════════════════════════════════════════════════════════════════════╣
║ HYPERSENSITIVITY (ACID)                                                  ║
║ Type I = IgE + mast cells = Anaphylaxis (<30 min) [Penicillin, pollen]  ║
║ Type II = IgG/IgM + complement = Cytotoxic [ABO mismatch, MG]          ║
║ Type III = Immune complexes = Tissue damage [SLE, serum sickness]       ║
║ Type IV = T cells = Delayed 48-72 hrs [Mantoux, contact dermatitis]     ║
╠══════════════════════════════════════════════════════════════════════════╣
║ SEROLOGICAL TESTS                                                        ║
║ Widal=Typhoid | VDRL=Syphilis | ELISA=HIV/HepB | Western Blot=HIV confirm║
║ Mantoux = TB | ANA = SLE | Coombs = Hemolytic anemia                    ║
╠══════════════════════════════════════════════════════════════════════════╣
║ VACCINES                                                                 ║
║ Live attenuated: BCG, OPV, MMR, Measles (strong, long immunity)         ║
║ Killed: IPV, DPT-whole cell, Hepatitis A (multiple doses needed)        ║
║ Toxoid: DPT, TT (against bacterial toxin)                               ║
║ Subunit/Recombinant: HepB, HPV, Pneumococcal, Acellular Pertussis       ║
╠══════════════════════════════════════════════════════════════════════════╣
║ COLD CHAIN IMPORTANT FACTS                                               ║
║ Heat-sensitive: OPV, BCG, Measles, MMR (store in freezer)               ║
║ Freeze-sensitive: DPT, TT, HepB, IPV, Pentavalent (store +2 to +8°C)  ║
║ VVM: inner square LIGHTER = usable ✅ | SAME/DARKER = discard ❌        ║
║ Reconstituted BCG/Measles/MMR: use within 4-6 hours                    ║
╠══════════════════════════════════════════════════════════════════════════╣
║ NATIONAL IMMUNIZATION SCHEDULE KEY POINTS                                ║
║ Birth: BCG (ID), OPV-0 (oral), HepB-0 (IM)                             ║
║ 6, 10, 14 weeks: OPV, Pentavalent, Rotavirus (+PCV & fIPV at 6 & 14 wk)║
║ 9-12 months: MR-1, PCV booster, Vit A                                   ║
║ 16-24 months: DPT B1, OPV B, MR-2, Vit A                               ║
║ 5-6 years: DPT Booster-2 | 10 & 16 years: Td                           ║
║ Pregnant women: TT/Td-1 + TT/Td-2 (4 weeks apart) → neonatal tetanus   ║
╠══════════════════════════════════════════════════════════════════════════╣
║ ANAPHYLAXIS MANAGEMENT                                                   ║
║ FIRST → ADRENALINE 0.5 mg IM (1:1000) outer thigh                      ║
║ Then: O₂, IV fluids, Chlorphenamine, Hydrocortisone                     ║
║ Observe 30 min post-vaccination; 6 hrs after anaphylaxis (biphasic)     ║
╚══════════════════════════════════════════════════════════════════════════╝

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