Immunity and Infection Lecture Notes

Examination Strategy and Preparation

Documentation and notes from today are essential for the upcoming examination scheduled in $3$ weeks.
Material specifically identified as relevant to the exam must be prioritized for review.
A successful student strategy involves reading assigned chapters and then revisiting primary notes to ensure highlighted exam-specific content is not overlooked.

Overview and Definitions of Immunity

Immunity is defined as the normal physiological response to disease-causing microorganisms and tossing substances, as well as conditions associated with the suppressor or accessory aspects of the immune system.
A high-functioning immune system allows the body to effectively void off pathogens.
Factors influencing immune response quality include nutrition, physical activity, and genetics.
The immune response exists on a spectrum ranging from hypo (suppressed) to hyper (exaggerated or over-reactive).
An example of a hyper-immune response is a wasp sting, where the immune system reacts excessively to protect the body, sometimes requiring an EpiPen (epinephrine injection) to calm the reaction down.

Classifications of Immunity

Innate Immunity u
- Present at birth.
- Does not identify specific antigens; it reacts identically to all foreign substances.
- Serves as the body’s first line of defense.
Acquired Immunity (Specific Immunity)
- Unique to specific identified antigens.
- Must be learned and developed by the body.
Active Acquired Immunity
- Occurs when a person is exposed to an antigen and develops a response.
- Can be induced naturally (exposure to an infected person) or artificially (through immunization).
Passive Acquired Immunity
- Occurs when antibodies produced by one person are transferred to another.
- Examples include the transfer of antibodies from a mother to a fetus across the placenta, or the transfer of colostrum and breast milk to a neonate.
- Artificial examples include the injection of gamma globulin (immunoglobulin) for individuals with low immunity, such as cancer patients.
- During COVID, passive immunity was utilized by hanging plasma from recovered patients for the treatment of active cases, which often proved more effective than antivirals.

Physiological Components of the Immune System

T cells: Described as the "Rocky" of the immune system; they are the primary cells that fight against harmful foreign invaders.
B cells: Work in conjunction with T cells in the immune response.
Phagocytes: Large cells that engulf and "eat" bad substances in the body, behaving similarly to the Pac-Man character.
Lymphocyte and Dendrite Cells: Additional critical specialized cells involved in the immune response.

Altered Immune Responses

Suppressed Immune Response (Hypo-immune)
- Individuals are referred to as immunocompromised.
- Consequences include increased susceptibility to bacterial, fungal, viral, and parasitic infections, as well as cancer.
- High-risk populations: Neonates, older adults, individuals with Leukemia or HIV, and those receiving chemotherapy or radiation.
- Neutropenic Precautions: Patients with a very low white blood cell count require protective measures, such as healthcare workers wearing masks, because the patient cannot adequately defend against microorganisms.
Exaggerated Immune Response (Hyper-immune)
- Often involves a genetic predisposition or family history of autoimmune diseases or atopy.
- Ranges from hay fever to life-threatening anaphylaxis.
- Anaphylaxis signs and symptoms are critical for examination review.
- Autoimmune diseases, such as Rheumatoid Arthritis or Lupus, occur when the immune system loses self-tolerance and destroys healthy cells.

Age-Related and Physiological Considerations in Immunity

Aging (Persons over $60$ )
- Fewer T lymphocytes were observed.
- Increased levels of autoantibodies.
- Methylglobulin levels and B lymphadenitis function are diminished.
- Delayed hypersensitivity responses occur.
- Decreased circulatory memory cells result in higher cancer and infection risks.
Pregnancy
- Pregnancy induces a state of maternal immune compromise to prevent the rejection of the fetus, which is technically a graft created by the father's antigens at the placenta connection.

Nursing Assessment and Symptoms of Altered Immunity

Immediate Monitoring: When starting a patient on a new antibiotic, wait and assess for $30$ minutes. Watch for itching, breakouts, or fever. If these occur, stop the antibiotic and contact the Healthcare Provider (HCP) immediately.
History: Assess past medical history, genetics, occupational hazards, and lifestyle behaviors (e.g., drug or alcohol addiction).
Suppressed Immune Findings:
- Frequent infections.
- Poor wound healing.
- Weight loss or wasting syndrome.
- Enlarged lymph nodes.
- Fatigue and malaise.
- Opportunistic infections (e.g., severe pneumonia in HIV patients).
Lupus Diagnosis: A complex diagnosis where doctors may run $13$ different tests; a patient is typically diagnosed definitively if they test positive for at least $11$ of them.

Diagnostic Testing for Immune Function

Red and White Blood Cell Count (WBC).
C-reactive Protein (CRP).
Erythrocyte Sedimentation Rate (ESR): High levels can indicate arthritis or lupus.
Allergy and Genetic Testing.
Rheumatoid Factors.
Western Blot Test: Specifically used for identifying HIV.
Torch Antibody Panel.
Organ Function Tests.

Infections: Definitions and Classifications

Infection: The invasion or multiplication of microorganisms in body tissues, leading to injury via competitive metabolism, toxins, or intracellular replication.
Commensal Relationship: The relationship between normal flora and the host. Because individuals have their own flora, they can perform self-catheterization at home with clean hands rather than a sterile field.
Sepsis: Pathogens present in the blood or tissues.
Virulence: The degree of pathogenicity or the capacity of a microorganism to cause disease.
Classification by Causation: Bacterial, Viral, Fungal, and Parasitic/Protozoal.
Spatial and Temporal Classifications:
- Localized: Restricted to one area.
- Systemic/Disseminated: Affects the whole body.
- Acute: Sudden onset.
- Chronic: Long-term.
- Hospital-acquired: Infections contracted within a healthcare facility (e.g., Catheter-associated Urinary Tract Infections/UTIs).

Epidemiology of Spread

Endemic: Constantly present at a low level in a community (e.g., Influenza in the United States, which causes approximately $20,000$ deaths annually).
Epidemic: New cases in a specific timeframe exceed expected numbers (e.g., $2010$ Cholera in Haiti, or periodic Measles outbreaks).
Pandemic: Global spread (e.g., COVID or HIV in the $1980$ s).

The Infectious Process and Complications

Mechanism: B and T lymphocytes activate, the complement system initiates, and bacteria release endotoxins or exotoxins which damage host cells and trigger inflammation.
Uncontrolled Infection: Leads to septic shock, multi-organ failure, and death. Figure $23.3$ in the text contains the specific signs and symptoms of septic shock.
Populations at Greatest Risk: The poor, the uninsured/under-insured, and the undernourished.
Overcrowding: Facilitates transmission; for example, Meningitis often spreads among college students in dorms through close contact and sharing items like razors.

Clinical Manifestations of Infection and Inflammation

Localized Symptoms: Redness, heat, edema (swelling), and pain.
Systemic Symptoms: Fever, fatigue, and malaise.
Wound Complications:
- Dehiscence: The unintended opening of a surgical wound (staples or stitches fail).
- Evisceration: The protrusion of internal organs through an open wound.
- Nursing Intervention for Evisceration: Place moist sterile gauze over the organ, call the HCP immediately, and monitor the patient for signs of shock.
Drainage: Serous drainage (clear or pinkish) is often a normal inflammatory response to a wound.

Thermoregulation and Pyrogens

Mechanism: Microorganisms stimulate WBCs to release pyrogens. Pyrogens reset the hypothalamus thermostat to a higher level.
Purpose: Fever is the body's natural mechanism to kill microbes.
Clinical Intervention: Antipyretics (Tylenol) are typically not administered for low-grade fevers (e.g., $99.3^{\circ}\text{F}$ ) because the fever is beneficial. Tylenol is usually indicated once temperature reaching $100.4^{\circ}\text{F}$ .

Infection Control and Nursing Interventions

Modifiable Risk Factors: Stress is a significant modifiable factor for immune health.
Hand Hygiene:
- Mandatory when entering and exiting a patient's room.
- Hand sanitizer is common, but C. diff (Clostridioides difficile) requires soap and water.
- Scrub for at least $15$ seconds.
- Remove rings and watches for surgical scrubs.
Precautions for Tuberculosis (TB):
- Must wear an N95 mask.
- Patient must be in a Negative Pressure Room.
- Gowning is recommended due to coughing.
Needle Stick Injury: Hepatitis B is the most common infection resulting from a dirty needle stick.
Hygiene Habits: Do not cross-contaminate food (e.g., chicken and meat on the same board). Use proper hand lotions only after washing to prevent skin breakdown, and keep nail tips short to prevent bacterial harboring.

Questions & Discussion

Question: In an exam setting, what is a modifiable risk factor for the immune system?
Response: Stress.
Question: When do you administer Tylenol for a fever?
Response: At $100.4^{\circ}\text{F}$ . A temperature of $99.3^{\circ}\text{F}$ does not require Tylenol as it is the body's natural response.
Question: What are the three things you do for an evisceration?
Response: Place moist sterile gauze over the organ, call the HCP immediately, and monitor for signs of shock.
Question: What kind of mask is required for a TB patient?
Response: An N95 mask.
Question: What is the most common infection from a dirty needle stick?
Response: Hepatitis B.
Question: What special hand hygiene is required for C. diff?
Response: Washing with soap and water (not sanitizer).

The ability of the human body to maintain health is reliant on multiple protective mechanisms, with the immune response being one of the most complex. Here’s a detailed breakdown of the concept of immunity, highlighting both normal and abnormal immune functions:

Definition of Immunity

Immunity is the physiological process that provides protection against disease, derived from the Latin word immunis, meaning exempt.
It involves a complex group of cells, tissues, and organs that work dynamically to protect against foreign substances, pathogens, and toxins, including bacteria, viruses, fungi, and environmental proteins.

Types of Immunity

Innate Immunity
- Present at birth, non-specific, includes physical barriers and inflammation.
Adaptive Immunity
- Specific and learned, involves humoral immunity (antibody production) and cell-mediated immunity (T lymphocytes). It can be Active (natural exposure or vaccination) or Passive (transfer of preformed antibodies from mother to fetus).

Optimal vs. Abnormal Immune Responses

An optimal immune response provides protection, removes damaged tissue, and identifies abnormal cells.
Abnormal responses may include:
- Suppressed Immune Response (immunodeficiency)
- Results in increased susceptibility to infections.
- Exaggerated Immune Response (hypersensitivity)
- Includes allergies, autoimmune disorders where the immune system incorrectly attacks its own tissues.

Components of the Immune System

Phagocytes: Key players in engulfing pathogens, primarily macrophages and neutrophils.
Antigen-Presenting Cells (APCs): Process and present antigens to T lymphocytes, include dendritic cells and B cells.
Lymphocytes:
- B Lymphocytes: Produce antibodies specific to antigens.
- T Lymphocytes: Includes helper T cells that activate other immune cells, cytotoxic T cells that kill infected cells, and suppressor T cells that regulate immune responses.

The Immune Response Process

Recognition of Antigens: Through MHC proteins on APCs that display foreign antigens to T cells.
Activation: T cells proliferate and differentiate, leading to B cell activation and antibody production.
Response: Antibodies neutralize pathogens, and T cells eliminate infected cells.

Age-Related Changes in Immunity

Immune function develops in infancy and may decline with age. Newborns rely on maternal antibodies, while older individuals often have reduced T cell immunity and an increased risk for autoimmune diseases and infections.

Risk Factors for Altered Immunity

Age: Infants (immature) and elderly (diminished immunity) are more susceptible.
Chronic Illness: Conditions like diabetes and HIV impact immune function.
Environmental Factors: Poor nutrition, pollutants, and stressors can depress immunity.

Assessment of Immune Function

Includes health history, physical examination, and lab tests for blood cell counts, specific antibodies, and screening for infections.

Management of Immune Disorders

Primary Prevention: Vaccinations and healthy lifestyle choices to minimize stress and risk factor exposure.
Secondary Prevention: Screenings for immune dysfunctions (e.g., HIV).
Treatment: Comprehensive care that often involves an interdisciplinary team for immune dysfunctions, along with medication for infections or autoimmune disorders.

Clinical Exemplars

Common diseases associated with immune dysfunction include HIV (results in immune suppression), allergies (hypersensitivity), and autoimmune diseases (e.g., rheumatoid arthritis, lupus).

Summary

The immune system is vital for health and well-being, requiring a balance between optimal functioning and the prevention of excessive reactions. Various factors including age, environment, and genetic predisposition play a crucial role in shaping immune responses and health outcomes.

Documentation and notes are essential for the upcoming examination scheduled in $3$ weeks.
Prioritize material specifically identified as relevant to the exam for review.
A successful student strategy involves reading assigned chapters and revisiting primary notes to ensure highlighted exam-specific content is not overlooked.
Immunity is the normal physiological response to disease-causing microorganisms and is influenced by factors such as nutrition, physical activity, and genetics.
Different types of immunity include Innate Immunity, which is present at birth and reacts non-specifically, and Acquired Immunity, which requires exposure to specific antigens.
- Active Acquired Immunity develops through exposure or vaccination.
- Passive Acquired Immunity involves the transfer of antibodies from one individual to another.
The physiological components of the immune system include T cells, B cells, phagocytes, and specialized lymphocyte and dendritic cells.
Immune responses can be suppressed (hypo-immune) or exaggerated (hyper-immune), with various clinical implications such as increased susceptibility to infections or allergic responses.
Age-related considerations include declining immune function in older adults and the effects of pregnancy on maternal immunity.
The nursing assessment should include monitoring for symptoms of altered immunity and comprehensive history-taking to identify risk factors for immune dysfunctions.
Infection classifications cover definitions, modes of transmission, and the distinction between localized and systemic infections, as well as acute and chronic forms.
points about infection control include the significance of hand hygiene, appropriate precautions for airborne infections like TB, and understanding modifiable risk factors that impact immune health.