Innate Immune System

Immune System

Defense system of the body against foreign invaders (pathogens)

Innate Immunity

Immediate, non-specific first and second line of defense present at birth

Adaptive Immunity

Delayed, specific immune response involving T and B cells

First Line of Defense

Non-specific barriers that prevent pathogen entry (physical, chemical, biological)

Second Line of Defense

Internal defenses activated when pathogens bypass surface barriers

Third Line of Defense

Adaptive immune response with memory cells for specific pathogens

Cytokines

Chemical signaling molecules that coordinate immune responses

PAMPs (Pathogen-Associated Molecular Patterns)

Common molecular structures found on pathogens

PRRs (Pattern Recognition Receptors)

Receptors that recognize PAMPs/MAMPs on pathogens

TLRs (Toll-Like Receptors)

Type of PRR on phagocytes that detect pathogens

Lysozyme

Enzyme that breaks down bacterial cell walls

Lactoferrin

Protein that binds iron to limit microbial growth

Hematopoiesis

Formation of blood cells in bone marrow

Neutrophils

First responders that engulf pathogens; most abundant WBC

Basophils

Cells that release histamine and promote inflammation

Macrophages

Long-lived phagocytes that engulf pathogens

Dendritic Cells

Antigen-presenting cells that activate adaptive immunity

Natural Killer (NK) Cells

Cells that kill virus-infected and cancer cells

Phagocytosis

Process of engulfing and destroying pathogens

Chemotaxis

Movement of immune cells toward infection signals

Interferons (IFNs)

Cytokines that inhibit viral replication

Opsonization

Tagging pathogens for easier phagocytosis

Diapedesis

Movement of WBCs out of blood vessels into tissues

Pyrogens

Cytokines that induce fever (e.g., IL-1)