NCLEX Review Guide: Adult Health - Immune Response

Types of Immunity

• Innate immunity is the body's first line of defense, including physical barriers (skin, mucous membranes) and chemical barriers (stomach acid, tears). This non-specific response activates immediately upon pathogen exposure.
• Adaptive immunity develops specific responses to particular antigens through B-cells (humoral immunity) and T-cells (cell-mediated immunity). This response has memory capabilities for faster future responses.
• Active immunity occurs when the body produces its own antibodies through infection or vaccination. Passive immunity involves receiving pre-formed antibodies from another source (maternal antibodies, immunoglobulin therapy).

White Blood Cell Types and Functions

• Neutrophils (50-70%) are the most abundant WBCs and first responders to bacterial infections, performing phagocytosis. Elevated levels indicate acute bacterial infection.
• Lymphocytes (20-40%) include B-cells that produce antibodies and T-cells that provide cell-mediated immunity. Elevated levels suggest viral infections or chronic inflammation.
• Monocytes (2-8%) transform into macrophages in tissues, engulfing pathogens and cellular debris. Increased levels indicate chronic infections or inflammatory conditions.
• Eosinophils (1-4%) primarily fight parasitic infections and are involved in allergic reactions. Elevated levels suggest allergies or parasitic infections.
• Basophils (<1%) release histamine during allergic reactions and contain heparin for anticoagulation. Increased levels are rare but may indicate allergic responses.

Acute Inflammation Process

1. Vasodilation occurs first, increasing blood flow to the affected area and causing redness and warmth
2. Increased vascular permeability allows fluid and cells to move from blood vessels into tissues, causing swelling
3. Cellular infiltration brings neutrophils first, followed by monocytes/macrophages to fight infection
4. Tissue repair begins with removal of debris and formation of new tissue

NCLEX Success Strategies

• Remember that fever is beneficial in fighting infection by enhancing immune cell function, but monitor for hyperthermia complications. Temperatures above 104°F (40°C) require immediate intervention.
• Understand that immunosuppressed patients may not show typical signs of infection due to decreased inflammatory response. Monitor for subtle changes in vital signs and mental status.
• Left shift in CBC indicates increased immature neutrophils (bands), suggesting acute bacterial infection requiring prompt antibiotic therapy.