Chapter 1 Flashcards
• Protective immunity against microbes is mediated by what?
the early reactions of innate immunity and the later responses of adaptive immunity.
What are innate responses stimulated by?
molecular structures shared by groups of microbes and by molecules expressed by damaged host cells
Adaptive immunity is specific for what?
for different microbial and nonmicrobial antigens and is increased by repeated exposures to antigen (immunologic memory).
what is humoral immunity mediated by?
B lymphocytes and their secreted products, antibodies, and functions in defense against extracellular microbes
what is cell mediated immunity mediated by?
T lymphocytes and their products, such as cytokines, and is important for defense against intracellular microbes.
how may immunity be acquired?
by a response to antigen (active immunity) or conferred by transfer of antibodies or cells from an immunized individual (passive immunity).
what are the properties that the immune system possesses that are of fundamental importance for its normal functions?
- specificity for different antigens,
- a diverse repertoire capable of recognizing a wide variety of antigens,
- memory of antigen exposure,
- the capacity for rapid expansion of clones of antigen-specific lymphocytes in response to the antigen,
- specialized responses to different microbes, maintenance of homeostasis,
- the ability to discriminate between foreign antigens and self antigens
lymphocytes are the only cells capable of what?
specifically recognizing antigens and are thus the principal cells of adaptive immunity
what are the two major subpopulations of lymphocytes?
are B cells and T cells, and they differ in their antigen receptors and functions. Specialized antigen-presenting cells capture microbial antigens and display these antigens for recognition by lymphocytes. The elimination of antigens often requires the participation of various effector cells
what initiates the adaptive immune response?
the recognition of foreign antigens by specific lymphocytes
what are the responses of lymphocytes?
by proliferating and by differentiating into effector cells, whose function is to eliminate the antigen, and into memory cells, which show enhanced responses on subsequent encounters with the antigen
what does the activation of lymphocytes require?
antigen and additional signals that may be provided by microbes or by innate immune responses to microbes.
what do CD4+ T lymphocytes do?
help macrophages to eliminate ingested microbes and help B cells to produce antibodies
what do CD8+ CTLs do?
CTLs kill cells harboring intracellular pathogens, thus eliminating reservoirs of infection
what do antibodies do?
the products of B lymphocytes, neutralize the infectivity of microbes and promote the elimination of microbes by phagocytes and by activation of the complement system
