Pathogen & Disease Test: Host Defenses Against Infectious Disease Flashcards
Non-specific Mechanisms
operate against a wide range of pathogens
- the body’s primary defense against disease
Non-specific Mechanisms: Anatomical Barriers
Examples:
- nasal opening traps airborne particles and prevents most of them from reaching the lungs; to the respiratory system
- the skull and vertebral column, which protect the central nervous system
- the skin; low moisture, low pH, and high salinity prevent most microorganisms from growing and multiplying on the skin
Non-specific Mechanisms: Physiological Deterrents
physiological refers to the normal function of an organism
Examples:
- tears, saliva, nasal secretions, sweat and blood contain lysozyme, an enzyme that breaks down bacterial cell walls
- vaginal secretions are acidic, hostile environment that prevent their growth
- white blood cells that are phagocytic
- clotting factors in blood plasma
- inflammatory response prevents infectious agents from spreading in the body
Non-specific Mechanisms: Normal Flora
- do not cause disease because their growth is kept under control by the host’s defense mechanisms and by the presence of other microorganisms
- these organisms protect the host by successfully competing with disease-causing organisms, preventing the latter from invading the host
- when the growth of the normal flora is suppressed, other opportunistic agents that normally do not grow in or on the body may be able to infect and cause disease
Specific Mechanisms
target particular pathogens and pathogen-infected cells for destruction
- the second, specific line of defense
Specific Mechanisms: Cell Mediated Response
- this response occurs when the lymphokines released from the helper T-cells stimulate other cell types to participate in the immune response
- involves T cells which are responsible for directly destroying body cells that are infected with a virus or have become cancerous, or for activating other immune cells to be more efficient microbe killers
What do Lymphokine-stimulated killer T cells do in a Cell Mediated Response?
they attach to pathogen-infected cells and destroy them
What do Lymphokine-activated phagocytic cells do in a Cell Mediated Response?
they produce more toxic molecules that can kill the pathogen directly
Specific Mechanisms: Antibody Mediated Response
- this response occurs when the lymphokines activate specific B-cells to produce antibodies
- involves both T and B cells
- the antibodies produced by the B-cells attach to antigens on the surface of pathogens and signal attack by phagocytic cells
- other B-cells becomes memory B-cells
Specific Mechanisms: Immunity
- when a host encounters an antigen that triggers a specific immune response for the second time, the memory lymphocytes recognize it and quickly being growing and dividing, as well as producing high levels of lymphokines and antibodies
- immune response occurs so quickly in a second encounter with the same pathogen, that the pathogen does not have enough time to reproduce to levels that result in disease
Specific Mechanisms: Vaccination
- is a killed or weakened (attenuated) strain of a particular pathogen, or a solution containing critical antigens from the pathogen
- the body’s immune system will respond to these vaccines ad if they contain the actual pathogen, even though the vaccine is not capable of causing the disease. As a result of the specific immune response, memory lymphocytes will be present that respond rapidly when the actual pathogen is encountered.
Eradication of Infectious Agents
How can pathogens evade immune response?
What are 3 reasons why viral diseases are not easily prevented by vaccinations?
- By acquiring an external coat composted of host derived material
- By disguising themselves by making molecules that resemble host molecules
- By mutating quickly, producing variants of their antigens that are not recognized by the hosts’ immune system
