Overview of the Immune System, Inflammation, Infection & Pneumonia

Vocabulary flashcards covering immune cells, inflammatory mediators, immunity types, infection concepts, transmission modes, and pneumonia-related terms for exam preparation.

Immune Responder

Collective term for organs, tissues, and cells (especially leukocytes) that participate in immune defense

Leukocytes (White Blood Cells)

Cells of the immune system that recognize self vs. non-self and mount protective actions

Neutrophils

Phagocytic leukocytes that arrive early at infection sites and destroy pathogens

Macrophages

Large phagocytes that engulf debris and microbes; also present antigens to T-cells

Eosinophils

Granulocytes involved in allergic reactions and defense against parasites

Basophils

Leukocytes that release histamine and other mediators of inflammation

Lymphocytes

White blood cells (B-cells & T-cells) central to adaptive immunity

Phagocytosis

Seven-step process by which cells ingest and destroy foreign material

Inflammation

Innate, immediate, nonspecific response to tissue injury or invasion

Five Cardinal Signs

Warmth, redness, swelling, pain, and loss of function—classic manifestations of inflammation

Stage I (Vascular)

Initial inflammatory phase with vasodilation, ↑permeability, redness & pain

Stage II (Cellular Exudate)

Phase marked by neutrophilia and pus formation

Stage III (Tissue Repair)

Wound healing phase involving growth factors, angiogenesis, and possible scar formation

Immunity

Adaptive internal protection that provides long-term resistance to specific antigens

Immunocompetence

Optimal functioning of inflammation, antibody-mediated and cell-mediated immunity

Natural Active Immunity

Long-lasting immunity gained after natural infection

Natural Passive Immunity

Temporary immunity from maternal antibodies via placenta or breast milk

Artificial Active Immunity

Immunity produced by vaccination with antigens

Artificial Passive Immunity

Immediate, short-term protection via injected antibodies

Antibody-Mediated Immunity (AMI)

Humoral response in which B-cells produce antibodies against antigens

Immunoglobulins

Antibody proteins (IgG, IgA, IgM, IgE, IgD) with specific immune roles

IgG

Most abundant antibody; crosses placenta; provides long-term systemic immunity

IgA

Antibody in secretions (saliva, breast milk) protecting mucosal surfaces

IgM

First antibody produced in primary response; potent complement activator

IgE

Antibody mediating allergic reactions and anti-parasite defense

IgD

Antibody acting as B-cell receptor; role still under investigation

Memory B-Cells

Long-lived cells that enable rapid secondary antibody responses

Cell-Mediated Immunity (CMI)

T-cell-driven defense that targets infected or abnormal self cells

Helper T-Cells (CD4+)

T-cells that coordinate immune responses by releasing cytokines

Cytotoxic T-Cells (CD8+)

T-cells that directly kill virus-infected and cancer cells

Suppressor T-Cells

T-cells that down-regulate immune responses to maintain self-tolerance

Natural Killer (NK) Cells

Lymphocytes that destroy virus-infected or tumor cells without prior sensitization

Cytokines

Small protein messengers (e.g., interleukins, interferons, TNF-α) guiding immune actions

Interleukins (ILs)

Cytokines mediating communication between leukocytes

Interferons (IFNs)

Cytokines that inhibit viral replication and modulate immunity

Tumor Necrosis Factor (TNF-α)

Cytokine involved in systemic inflammation and fever

Hematopoietic Stem Cell

Multipotent stem cell in bone marrow giving rise to all blood cells

Myeloid Progenitor Cell

Stem cell lineage that produces RBCs, platelets, neutrophils, etc.

Lymphoid Progenitor Cell

Stem cell lineage that generates B-cells, T-cells, and NK cells

Histamine

Mediator causing vasodilation and increased vascular permeability

Bradykinin

Peptide mediator contributing to pain and vasodilation

Complement System

Cascade of plasma proteins (e.g., C3a, C5a) enhancing inflammation and lysis

Prostaglandins

Lipid mediators (e.g., PGE2) causing pain, fever, and vasodilation

Leukotrienes

Lipid mediators involved in chemotaxis and vascular permeability

Pathogen

Microorganism capable of causing disease

Infection

Invasion and replication of pathogens in tissue leading to damage

Virulence

Degree of pathogenicity and ability to cause disease

Normal Flora

Microbes that normally inhabit the body without causing disease

Colonization

Presence and growth of microbes on body surfaces without tissue invasion

Exotoxin

Protein toxin secreted by bacteria into host tissues

Endotoxin

Toxin within Gram-negative bacterial cell walls released on lysis

Chain of Infection

Six links: agent, reservoir, portal exit, transmission, portal entry, susceptible host

Direct Contact Transmission

Disease spread by physical person-to-person touch

Droplet Transmission

Infection via large respiratory droplets traveling <1 meter

Airborne Transmission

Spread by tiny particles that remain suspended and travel distances

Vector-Borne Transmission

Pathogen carried by insects/animals (e.g., mosquitoes, ticks)

Vehicle-Borne Transmission

Spread through contaminated food, water, or substances

Vertical Transmission

Pathogen transfer from mother to child during pregnancy, birth, or breastfeeding

Physical Barriers

First-line defenses such as intact skin and mucous membranes

Hospital-Acquired Infection (HAI)

Infection acquired ≥48 h after admission; prevented by strict precautions

Standard Precautions

Assumption that all body fluids are infectious; use of PPE & hand hygiene

Transmission-Based Precautions

Additional infection controls (Airborne, Droplet, Contact) for specific pathogens

Pneumonia

Inflammation and fluid in alveoli due to infection or aspiration

Community-Acquired Pneumonia (CAP)

Pneumonia contracted outside healthcare settings

Hospital-Acquired Pneumonia (HAP)

Pneumonia developing ≥48 h after hospital admission

Ventilator-Associated Pneumonia (VAP)

Pneumonia occurring ≥48 h after intubation

Aspiration Pneumonia

Lung infection caused by inhalation of oropharyngeal contents

Productive Cough

Cough that expels purulent sputum, common in pneumonia

Crackles

Rales; fine lung sounds indicating fluid in alveoli

Semi-Fowler’s Position

Head of bed elevated 30–45° to improve breathing

Bronchodilators

Medications that relax bronchial smooth muscle to widen airways