Pathogens Flashcards
Pathogens
infectious agents that cause disease or infection
Types of pathogens
- bacteria
- viruses
- protozoans
- fungi
- parasitic worms
- prions (infections proteins)
Three lines of Body’s Defense
1) Chemical and physical barriers
2) Internal cellular and chemical defenses
3) Immune responses
Physical Barriers
skin and mucous membranes
Chemical barriers
hydrochloric acid, pepsin, and saliva
interferons
- proteins released by virus-infected cells
- attract natural killer cells and macrophages
- signal neighboring cells to produce proteins that inhibit viruses replication
compliment system
group of proteins that enhance body defenses
Functions of compliment system
- circulate in blood, activate when infection is detected
- punch holes in membranes of invading cells
- attract macrophages and neutrophils
- stimulate blood vessel widening (inflammation)
What causes the redness of inflammation?
blood vessels dilating in response to histamine
What causes the heat of inflammation?
increased blood flow; increases metabolic rate of cells in infected area
What do T Lymphocytes protect against?
cellular pathogens and abnormal cells
What do B Lymphocytes protect against?
extracellular toxins, viruses, bacteria
major histocompatibility complex (MHC) “markers”
proteins that label the body cells as “self” or “good”
antigens
molecules on the surface of invading cells recognized by defensive cells as “enemy”
Steps of Adaptive Immune Response
1) Threat
2) Detection
3) Alert
4) Alarm (activation)
5) Attack (defense)
6) Continued surveillance
Helper T Cells
contain different receptors that recognize specific antigens
Threat
pathogen evades first two lines of defense and enters body
Detection
macrophages (or B cells) encounter pathogen, engulfs and digests it; then places some antigens from pathogen onto its surface
Alert
‘antigen presenting cell’ encounters a specific Helper T cell that recognizes the antigen
Alarm (activation)
helper T cell secretes message that activates T cells or B cells with ability to recognize the particular antigen
Attack (defense)
appropriate B and T cells activate and start rapid mitotic division making ‘effector cells’ that recognize and attack the invading pathogen
Continued surveillance
- memory cells can recognize and respond to specific antigen if it re-invades
- second response to an antigen is much quicker and more robust
