23 Questions
Which type of cells are responsible for seeking, ingesting, and killing pathogens through phagocytosis?
Phagocytes
What is the process by which leukocytes pass through the walls of small capillary blood vessels within tissues to reach pathogens located in infected tissue called?
Extravasation
Which type of leukocytes are the first to arrive within hours of a bacterial infection?
Neutrophils
What are the molecular structures that are common to many groups of pathogenic microbes called?
PAMPs
What is the process called when the pathogen is engulfed in a vesicle and brought into the internal compartment of the phagocyte?
Phagocytosis
What is the name of the process by which phagocytes transition from a dormant state of readiness and slow proliferation to a state of hyperactivity, proliferation, production/secretion of cytokines, and enhanced intracellular killing?
Activation
What is the name of the process by which leukocytes stick slightly to the adhesion molecules, slowing down and rolling along the blood vessel walls near the infected area, before binding to even more of these adhesion molecules and squeezing through the cellular junction?
Extravasation
What is the name of the process by which the phagosome containing the pathogen fuses with one or more lysosomes, forming a phagolysosome, which enhances the acidification, essential for activation of pH-dependent digestive lysosomal enzymes and production of hydrogen peroxide and toxic reactive oxygen species?
Lysosomal fusion
Which enzymes digest the pathogen in the phagolysosome?
Lysosomal enzymes
What are macrophages and dendritic cells also involved in, in addition to being antigen-presenting cells involved in the specific adaptive immune response?
Extravasation
What are the molecular structures on phagocytes that recognize pathogen-associated molecular patterns (PAMPs) called?
PRRs
Which of the following is the main function of phagocytes?
To ingest and kill pathogens
What is the process by which leukocytes pass through the walls of small capillary blood vessels within tissues to reach pathogens located in infected tissue?
Extravasation
Which type of leukocyte is the first to arrive during a bacterial infection?
Neutrophils
What are the molecular structures that phagocytes can recognize and are common to many groups of pathogenic microbes called?
Pathogen-associated molecular patterns (PAMPs)
What is the process called when a phagocyte transitions from a dormant state of readiness to a state of hyperactivity, proliferation, and enhanced intracellular killing?
Activation
What is the process called when a pathogen is engulfed in a vesicle and brought into the internal compartment of the phagocyte?
Phagocytosis
What is the name of the process by which lysosomal enzymes such as lysozyme, phospholipase, and proteases digest the pathogen?
Digestion
What is the name of the process by which the phagosome containing the pathogen fuses with one or more lysosomes, forming a phagolysosome?
Lysosomal fusion
What is the name of the internal storehouse of microbicidal defensin proteins that some phagocytes contain?
Granules
Which type of cells are involved in the specific adaptive immune response and further process the remains of the degraded pathogen?
Macrophages and dendritic cells
What is the name of the process by which leukocytes stick slightly to the adhesion molecules, slowing down and rolling along the blood vessel walls near the infected area?
Adhesion
What is the name of the process by which the phagocyte transitions from a state of hyperactivity and proliferation to a state of slow proliferation and readiness?
Deactivation
Study Notes
Phagocytes: Mechanisms of Pathogen Recognition and Destruction
- Phagocytes are cells whose main function is to seek, ingest, and kill pathogens through phagocytosis.
- Phagocytes provide a strong, swift, and effective defense against a broad range of microbes, making them a critical component of innate nonspecific immunity.
- Extravasation, or diapedesis, is the process by which leukocytes pass through the walls of small capillary blood vessels within tissues to reach pathogens located in infected tissue.
- Leukocytes passing through will stick slightly to the adhesion molecules, slowing down and rolling along the blood vessel walls near the infected area, before binding to even more of these adhesion molecules and squeezing through the cellular junction in a process known as transendothelial migration.
- Neutrophils are the first to arrive, often within hours of a bacterial infection, while monocytes may take several days to leave the bloodstream and differentiate into macrophages.
- Phagocytes can recognize molecular structures that are common to many groups of pathogenic microbes, called pathogen-associated molecular patterns (PAMPs), through pattern recognition receptors (PRRs) such as toll-like receptors (TLRs).
- PRRs on macrophages provide an intracellular signal that activates the phagocyte, causing it to transition from a dormant state of readiness and slow proliferation to a state of hyperactivity, proliferation, production/secretion of cytokines, and enhanced intracellular killing.
- Once pathogen recognition and attachment occur, the pathogen is engulfed in a vesicle and brought into the internal compartment of the phagocyte in a process called phagocytosis.
- Acidification of the phagosome provides an important early antibacterial mechanism, and the phagosome containing the pathogen fuses with one or more lysosomes, forming a phagolysosome, which enhances the acidification, essential for activation of pH-dependent digestive lysosomal enzymes and production of hydrogen peroxide and toxic reactive oxygen species.
- Lysosomal enzymes such as lysozyme, phospholipase, and proteases digest the pathogen, and reactive oxygen and nitrogen compounds are also produced to degrade microbes.
- Some phagocytes even contain an internal storehouse of microbicidal defensin proteins, which can be released into the area around the cell to degrade microbes externally.
- Macrophages and dendritic cells are also antigen-presenting cells involved in the specific adaptive immune response, further processing the remains of the degraded pathogen and presenting key antigens on their cellular surface, an important step for stimulation of some adaptive immune responses.
Test your knowledge of phagocytes and their role in recognizing and destroying pathogens with this quiz. Learn about the mechanisms of extravasation, pathogen recognition patterns, and the phagocytosis process. Discover the importance of acidification and lysosomal enzymes in destroying bacteria and the role of macrophages and dendritic cells in the adaptive immune response. This quiz is perfect for anyone interested in immunology and the body's defense mechanisms.
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