The immune system protects the body through innate immunity (skin, mucosa, neutrophils, macrophages, complement, inflammation — fast and nonspecific) and adaptive immunity (specific, with memory):

• Humoral immunity — B cells become plasma cells that make antibodies: IgG (most abundant; crosses the placenta), IgM (first made in infection), IgA (secretions, breast milk), IgE (allergy and parasites), IgD
• Cell-mediated immunity — T cells: CD4 helper cells coordinate the response; CD8 cytotoxic cells kill infected or abnormal cells

Immune disorders fall into three groups: hypersensitivity (an excessive response), autoimmunity (a response against self), and immunodeficiency (an inadequate response).

Hypersensitivity reactions

Autoimmune disorders arise when tolerance to self fails, influenced by genes, hormones (most are more common in women), infections, and environment (e.g., ultraviolet light in SLE).

Immunodeficiency

• Primary (inherited): e.g., severe combined immunodeficiency, common variable immunodeficiency
• Secondary (acquired, far more common): HIV infection, chemotherapy, corticosteroids and immunosuppressants, malnutrition, diabetes, aging, splenectomy, kidney failure

HIV infection — HIV infects CD4 T cells. Without treatment, CD4 counts fall over years until opportunistic infections and cancers appear. AIDS (stage 3) = CD4 count below 200 cells/mm³ or an AIDS-defining illness. Transmission is through blood, sexual contact, and mother-to-child (pregnancy, birth, breastfeeding) — not through casual contact, shared dishes, or insects.

Anaphylaxis — sudden onset after exposure:

• Skin: urticaria, flushing, angioedema (lips, tongue, face)
• Airway and breathing: throat tightness, hoarseness, stridor, wheezing, dyspnea
• Circulation: hypotension, tachycardia, dizziness, collapse
• GI: cramping, vomiting, diarrhea

Systemic lupus erythematosus (SLE) — usually women of childbearing age: fatigue, fever, malar (butterfly) rash, photosensitivity, oral ulcers, symmetric arthritis, pleuritis or pericarditis, cytopenias, and lupus nephritis (the most common serious organ involvement — proteinuria, edema, hypertension, rising creatinine).

Rheumatoid arthritis (RA) — symmetric inflammation of small joints of hands and feet, morning stiffness lasting more than 1 hour, warm swollen joints, fatigue, and later deformities (ulnar deviation, swan-neck).

Myasthenia gravis — antibodies block acetylcholine receptors: fluctuating weakness that worsens with activity, ptosis, diplopia, and difficulty chewing and swallowing. Myasthenic crisis with respiratory muscle failure is the most dangerous complication.

HIV/AIDS — acute infection may resemble flu (fever, rash, sore throat, swollen nodes). Later: weight loss, chronic diarrhea, night sweats, and opportunistic conditions such as oral candidiasis (thrush), Pneumocystis pneumonia (dry cough, dyspnea, hypoxemia), Kaposi sarcoma, toxoplasmosis, cytomegalovirus retinitis, and tuberculosis.

Anaphylaxis

1. Epinephrine IM immediately into the mid-outer thigh: 0.01 mg/kg of 1 mg/mL solution, maximum 0.5 mg in adults (0.3 mg in children); repeat every 5–15 minutes if needed. No absolute contraindication in anaphylaxis
2. Call for help; remove the trigger (stop the infusion)
3. Position supine with legs raised (sitting if breathing is difficult; left side if pregnant); do not let the client stand or walk suddenly
4. High-flow oxygen; IV access and isotonic fluid boluses for hypotension
5. Adjuncts after epinephrine: inhaled albuterol for bronchospasm, H₁ antihistamines for itching and hives. Antihistamines and corticosteroids do not replace epinephrine and do not treat airway obstruction or shock
6. Clients on beta blockers may respond poorly — glucagon may be ordered
7. Observe for biphasic reaction; discharge with two epinephrine devices and an action plan

Latex allergy — latex-free equipment and room; cross-reactions with banana, avocado, kiwi, and chestnut.

Drug safety

HIV

• Start ART for everyone with HIV as soon as possible, regardless of CD4 count; lifelong adherence is essential
• Undetectable = untransmittable: a durably undetectable viral load prevents sexual transmission
• Opportunistic infection prophylaxis by CD4 level (e.g., trimethoprim-sulfamethoxazole for CD4 below 200 against Pneumocystis — watch for rash, hyperkalemia, marrow suppression)
• Pre-exposure prophylaxis (PrEP) for people at risk: daily oral tenofovir-based pills, injectable cabotegravir, or twice-yearly injectable lenacapavir. Confirm a negative HIV test before starting and retest every 2–3 months — PrEP alone in undiagnosed HIV causes drug resistance; check kidney function with oral tenofovir
• Post-exposure prophylaxis (PEP): start as soon as possible — ideally within hours — and no later than 72 hours after exposure; continue for 28 days

Listed in priority order.

1. Airway and circulation in anaphylaxis — epinephrine first, position, oxygen, fluids; prepare for intubation if angioedema progresses
2. Infection prevention in immunodeficiency and immunosuppression
   • Standard precautions for all clients, including those with HIV; extra isolation is not needed for HIV itself (transmission-based precautions only for specific infections such as tuberculosis)
   • Hand hygiene, early recognition of fever, safe food handling
3. Respiratory monitoring in myasthenia gravis — vital capacity, swallowing, cough strength
4. Medication safety — correct methotrexate schedule, steroid tapering, ART adherence
5. Symptom care
   • Oral candidiasis: soft, bland, lukewarm foods; avoid spicy, acidic, hot, or hard foods; gentle oral care; antifungals as ordered
   • Joint pain: rest inflamed joints, heat for stiffness and cold for acute inflammation, range-of-motion exercise
   • Fatigue: pace activities
6. Psychosocial — stigma (HIV), body image (rash, deformities), chronic illness coping; confidentiality

• Allergy: avoid triggers, wear medical identification, carry two epinephrine auto-injectors (or another approved epinephrine device), use at the first signs, then call emergency services
• SLE: avoid sun exposure, use broad-spectrum sunscreen and protective clothing; take hydroxychloroquine consistently; plan pregnancy when disease is quiet; report edema, foamy urine, fever
• RA joint protection: use larger, stronger joints (carry bags on the forearm, push doors with the palm or shoulder), do not load the finger joints, avoid staying in one position for long, use assistive devices, exercise regularly
• Do not take supplements claimed to "boost immunity" without advice; do not stop steroids or adjust doses on your own; avoid NSAIDs and aspirin self-medication without discussing bleeding and kidney risk
• HIV: take ART every day; use condoms and PrEP for partners as appropriate; routine vaccines (inactivated) are encouraged; practice food and water safety

• Type I = IgE (anaphylaxis, asthma, allergic rhinitis); type II = cytotoxic (transfusion reaction); type III = immune complex (serum sickness, SLE); type IV = delayed T cell (contact dermatitis, TB skin test)
• Epinephrine IM, mid-outer thigh, 0.01 mg/kg, max 0.5 mg adult — first and without delay
• Antihistamines and steroids are adjuncts only
• SLE: avoid sunlight; lupus nephritis is the key organ threat; anti-dsDNA and low complement track activity
• RA joint protection: large joints and palms, not fingers
• Methotrexate: weekly, folic acid, no alcohol, teratogenic
• Myasthenia gravis: most dangerous complication is respiratory muscle failure
• HIV: standard precautions; ART for all; AIDS = CD4 < 200 or AIDS-defining illness
• Oral thrush: soft, bland, lukewarm food
• PEP within 72 hours; U = U