Key Terms
Three types
Cellular barriers, mechanical defenses, microbiome.
Resident microbiota defend the host by
1. Occupying cellular binding sites — pathogens cannot attach 2.
Definition
System-wide inflammatory response; overall increase in body temperature. Regulated by the hypothalamus.
Hematopoiesis
Process by which all formed elements differentiate from pluripotent hematopoietic stem cells (HSCs) in the bone marrow.
Three antimicrobial mechanisms
1. Phagocytosis: engulf and destroy bacteria using defensins and hydrolytic enzymes in granules 2.
Degranulation
Release of granule contents (toxic molecules) into surrounding tissue Diapedesis: synonym for extravasation; exit of leu
NET proteins include
Lactoferrin, gelatinase, cathepsin G, myeloperoxidase
Kill mechanisms
1. Cytotoxic membrane proteins and cytokines that induce apoptosis in target cell 2.
When monocytes leave bloodstream and enter tissues
They differentiate into macrophages and dendritic cells (collectively: mononuclear phagocyte system)
Where it occurs
Capillaries only — NOT arteries or veins (walls too thick; arterial blood flow too turbulent for rolling adhesion)
Steps
1. Phagocyte recognizes pathogen (via opsonins, PRRs, or proximity) 2.
Opsonin-dependent recognition
Pathogens coated with opsonins (C1q, C3b, C4b, antibodies, mannose-binding proteins) are more easily recognized and engu
Opsonin-independent recognition
Phagocytes detect pathogen-associated molecular patterns (PAMPs) — molecular structures common to broad classes of patho
Pattern recognition receptors (PRRs)
Phagocyte receptors that bind PAMPs
Purpose
Recruit cellular defenses, eliminate pathogens, remove damaged cells, initiate repair. Risk: excessive inflammation caus