The Innate Immune System Flashcards
the innate systems lines of defense
- many of the nonspecific defenses are noncellular
eg: skin, mucus, tears and saliva, stomach acid, the complement system, and interferons
the skin
it acts as a physical barrier and secretes antimicrobial compounds
mucus
mucus on the mucous membranes traps pathogens; in the respiratory system, the mucus is propelled upward by cilia and can be swallowed or expelled
tears and saliva
both contain lysozyme, an antibacterial compound
the stomach
this produces acid, killing most pathogens. colonization of the gut helps prevent overgrowth by pathogenic bacteria through competition
the complement system
this can punch holes in the cell walls of bacteria, making them osmotically unstable
interferons
these are given off by virally infected cells and help prevent viral replication and dispersion to nearby cells
many of the nonspecific defenses are also acellular
macrophages, dendritic cells, natural killer cells, granulocytes
Macrophages
these ingest pathogens and present them on major histocompatibility complex (MHC) molecules. they also secrete cytokines
MHC class I (MHC-I)
this is present in all nucleated cells and displays endogenous antigen (proteins form within the cell) to cytotoxic T-cells (CD8+ cells)
MHC class II (MHC-II)
this is present in professional antigen-presenting cells (macrophages, dendritic cells, some B-cells, and certain activated epithelial cells) and displays exogenous antigen (proteins from outside the cell) to helper T-cells (CD4+ cells)
dendritic cells
these are antigen-presenting cells in the skin
natural killer cells
attack cells not presenting MHC molecules, including virally infected cells and cancer cells
granulocytes
these include neutrophils, eosinophils, and basophils
neutrophils
these ingest bacteria, particularly opsonized bacteria (those marked with antibodies). they can follow bacteria using chemotaxis
