Immune & Infection Overview
Three ways the immune system goes wrong — plus the germs that exploit it.
Problems with immunity fall into three patterns, and it helps to keep them straight:
- Immunodeficiency
- Too little immunity — can't fight infection. Example: HIV/AIDS.
- Autoimmune
- Immunity misfires — attacks the body's own tissues. Example: Lupus, rheumatoid arthritis.
- Hypersensitivity
- Immunity overreacts — allergic response. Example: Anaphylaxis, allergies.
For immune disorders, ask: is the client too weak to fight infection (protect them) or is the immune system attacking the body (calm it with immunosuppressants — which then weakens defenses)? For infection, the theme is always breaking the chain with hand hygiene and the correct precautions.
Every key point in this guide fits on one free printable page. Jump to the free cheatsheet PDF →
HIV / AIDS
A virus that disables the immune system's coordinator.
HIV attacks CD4+ T-helper cells — the cells that coordinate the immune response. As CD4 cells fall, the body loses its ability to fight infection.
- Transmission: blood, sexual fluids, and mother-to-baby (pregnancy, birth, breast milk). NOT casual contact — hugging, sharing utensils, saliva, sweat, or toilet seats.
- CD4 count measures immune strength. AIDS is diagnosed when CD4 falls below 200 cells/mm³ or an AIDS-defining opportunistic infection occurs.
- Opportunistic infections (e.g., Pneumocystis pneumonia) take hold when immunity is low.
- ART (antiretroviral therapy) suppresses the virus; strict adherence is critical to prevent resistance.
Because HIV is bloodborne, standard precautions protect caregivers — special isolation is not needed for HIV itself. (Isolation may be added if the client has a specific opportunistic infection like TB.) Teaching clients that HIV is not spread by casual contact reduces fear and stigma.
Autoimmune Disorders
When the immune system attacks the body's own tissue.
- Systemic lupus erythematosus (SLE) — a chronic, multi-organ autoimmune disease. Hallmarks: a butterfly (malar) rash across the cheeks and nose, photosensitivity, joint pain, fatigue, and possible kidney involvement (lupus nephritis). Teach sun protection and energy conservation.
- Rheumatoid arthritis (RA) — autoimmune inflammation of the joints, classically symmetric (both sides) with morning stiffness. Differs from osteoarthritis (OA), which is wear-and-tear and usually asymmetric.
Autoimmune diseases are often treated with corticosteroids and immunosuppressants to calm the overactive immune system. The trade-off: these drugs increase infection risk, so clients need careful infection monitoring and teaching, and steroids are never stopped abruptly.
Allergy & Anaphylaxis
When the immune system overreacts to a harmless trigger.
Allergic reactions range from mild (hives, itching) to anaphylaxis — a severe, life-threatening reaction.
Anaphylaxis
- Signs: airway swelling, wheezing/difficulty breathing, hypotension, widespread hives, and a feeling of impending doom.
- Treatment: epinephrine IM first (opens the airway, raises BP), then maintain the airway, high-flow oxygen, IV fluids, and antihistamines/corticosteroids. Remove the trigger (e.g., stop the IV drug).
In anaphylaxis, epinephrine is the priority and most life-saving treatment — given intramuscularly (often the lateral thigh). Antihistamines and steroids are helpful but secondary. Always identify and remove the trigger, and watch for a second (biphasic) reaction hours later.
The Chain of Infection
Six links a germ needs — break any one to stop spread.
Infection control means breaking any link in this chain. The single most effective action is hand hygiene, which interrupts the mode of transmission. Other links are broken by sterilizing equipment, covering coughs, using PPE, and supporting the host's immunity.
Sepsis & Septic Shock
A body-wide response to infection — and a time-critical emergency.
Sepsis is a life-threatening, body-wide response to infection that can damage organs. It can progress to septic shock (dangerously low blood pressure that doesn't respond to fluids — a type of distributive shock).
Early Recognition
- Fever (or sometimes low temperature), tachycardia, tachypnea
- High white blood cell count and rising lactate
- Altered mental status (confusion) and decreasing urine output
Outcomes depend on speed. The bundle is: obtain blood cultures first, then give broad-spectrum antibiotics early (ideally within the first hour) and IV fluids, and measure lactate. Early recognition of the subtle signs — especially in older adults, who may just become confused — is what saves lives.
Isolation Precautions
Standard for everyone — then add transmission-based as needed.
Standard precautions are used for every client (hand hygiene, gloves, and PPE as needed for contact with body fluids). Specific organisms add a transmission-based layer:
- Contactgown + gloves
- MRSA, VRE, C. diff, RSV.
- Dropletsurgical mask (within ~3–6 ft)
- Influenza, pertussis, bacterial meningitis, mumps.
- AirborneN95 + negative-pressure room
- TB, measles, varicella (chickenpox).
1) C. difficile is contact precautions, but you must wash hands with soap and water — alcohol gel does NOT kill C. diff spores. 2) Remember airborne diseases with "My Chicken Hez TB" — Measles, Chickenpox (varicella), and TB need an N95 and a negative-pressure room.
? A patient has active TB. What type of isolation is required, and what PPE does the nurse wear?
Infection Control & Nursing Care
The everyday practices that prevent spread.
- Hand hygiene — the #1 measure; before and after every client contact.
- PPE — gloves, gown, mask, eye protection based on the precaution; don (put on) and doff (remove) in the correct order to avoid self-contamination.
- Protective (reverse) isolation — for immunocompromised clients (e.g., neutropenic), to protect them from germs.
- Asepsis — medical asepsis (clean technique) vs surgical asepsis (sterile technique) for invasive procedures.
- Teach clients about completing antibiotic courses, vaccination, and hand hygiene at home.
When the client is the vulnerable one (HIV/AIDS, chemotherapy, immunosuppressants), the goal flips from "contain the germ" to "keep germs away from the client": meticulous hand hygiene, no sick visitors, no fresh flowers or raw produce, and prompt attention to any sign of infection.
Key Medications
The drug classes tied to immune and infectious disease.
- Antiretrovirals (ART)
- Suppress HIV — lifelong, strict adherence.
- Antibiotics
- Bacterial infections, sepsis (give early; cultures first).
- Antifungals / antivirals
- Opportunistic and viral infections.
- Corticosteroids / immunosuppressants
- Autoimmune disease (raise infection risk; don't stop steroids abruptly).
- Epinephrine
- First-line for anaphylaxis.
- Antihistamines
- Allergic reactions (secondary in anaphylaxis).
Anchor on the logic: immunodeficiency = protect the client; autoimmune = calm the immune system (and watch for infection from the treatment); allergy = remove the trigger and give epinephrine for anaphylaxis; infection = break the chain with hand hygiene and the right precaution; sepsis = recognize early and treat fast. The cheatsheet puts it on one page.
Frequently Asked Questions
Common student questions on this topic.
How is HIV transmitted, and what is the CD4 count?
What is the difference between an autoimmune disorder and an immunodeficiency?
How is anaphylaxis treated?
What is the chain of infection?
What are the early signs of sepsis?
What are the types of transmission-based isolation precautions?
Quick-Reference Cheatsheet
Every key point from this guide on a single printable page.
Immune & Infectious Disease Cheatsheet
One-page PDF — free download.