Innate Immunity and Pathogen Defense Mechanisms

Innate Immunity

Immediate immune response without memory or adaptation.

Adaptive Immunity

Immune response that adapts and remembers pathogens.

Pathogens

Microorganisms that cause disease, including viruses and bacteria.

Viruses

Intracellular pathogens that replicate inside host cells.

Bacteria

Extracellular pathogens that can be gram positive or negative.

Parasites

Larger pathogens requiring different immune strategies.

Gram Positive Bacteria

Thick peptidoglycan wall, resistant to MAC complement.

Gram Negative Bacteria

Thin peptidoglycan layer with tough outer membrane.

Penicillin

β-lactam antibiotic inhibiting peptidoglycan synthesis.

Neutrophil Extravasation

Process of neutrophils moving from blood to tissue.

Chemokines

Signaling molecules that attract immune cells to infection.

Tethering

Neutrophil attachment to endothelial cells via selectins.

Adhesion

Strong binding of neutrophils to ICAM-1 on endothelium.

Diapedesis

Neutrophils squeezing through endothelial cells into tissue.

Chemotaxis

Neutrophil movement along a chemokine gradient.

Opsonization

Coating pathogens with molecules to enhance phagocytosis.

Complement System

Proteins that enhance immune response and opsonization.

Phagocytosis

Process by which cells engulf and digest pathogens.

Fc Receptors (FcR)

Receptors on phagocytes that bind antibodies.

Pattern Recognition Receptors (PRR)

Receptors that recognize unique microbial molecules.

Pathogen Associated Molecular Patterns (PAMPs)

Unique molecules recognized by PRRs on pathogens.

Toll-Like Receptors (TLR)

PRRs that trigger innate immune responses.

TLR4

Binds lipopolysaccharide (LPS) from gram-negative bacteria.

LPS

Bacterial component causing strong immune response and fever.

Neutrophil Phagocytosis

Neutrophils engulf opsonized bacteria like S. aureus.

C5a

Chemoattractant that directs neutrophil migration.

Myeloid Cells

Immune cells involved in phagocytosis and inflammation.

Degranulation

Release of cytotoxic chemicals from immune cells.

NFκB

Nuclear factor activated by TLR signaling pathways.

Immunological Memory

Ability of adaptive immunity to remember past infections.