Chapter 4, Innate immunity
Overview of innate immunity
Innate immunity refers to defense mechanisms that are always present, ready to combat
microbes and other offending agents. It provides early defense, before adaptive immune
responses can develop.
Functions of innate immune responses
The two major types of protective reactions of the innate immune system are inflammation
and antiviral defense. Inflammation is the process by which circulating leukocytes and
plasma proteins are brought into sites of infection in tissues and are activated to destroy and
eliminate the offending agents. Antiviral defense mechanisms prevent virus replication and
promote killing of infected cells, thus eliminating reservoirs of viral infection without an
inflammatory reaction.
The functions of innate immune responses have some
important general features:
- Physical and chemical defenses at epithelial barriers,
such as the skin and lining of the gastrointestinal and
respiratory tracts, block microbial entry.
- Innate immune responses are the initial reactions to
microbes that serve to control or eliminate infection
of the host by many pathogens. These responses are
activated by microbes that traverse epithelial barriers.
- Innate immunity eliminates damaged cells and initiates the process of tissue repair.
- Innate immune responses stimulate adaptive immune responses and can influence
the nature of the adaptive responses to make them optimally effective against
different types of microbes.
Comparative features of innate and adaptive immunity
Important differences between innate and adaptive:
- Innate immune effector cells and molecules are present in sufficient quantities even
before infection and are fully functional or quickly become activated by microbes to
prevent, control, or eliminate infections. In contrast, effective adaptive immune
responses to a newly introduced microbe develop over several days as clones of naive
antigen-specific lymphocytes expand and differentiate into functional effector cells.
- For most innate responses to microbes, there is no appreciable change in the quality
or magnitude of the response upon repeated exposure—that is, there is little or no
memory. In contrast, repeated exposure to a microbe enhances the rapidity,
magnitude, and effectiveness of adaptive immune responses.
Overview of innate immunity
Innate immunity refers to defense mechanisms that are always present, ready to combat
microbes and other offending agents. It provides early defense, before adaptive immune
responses can develop.
Functions of innate immune responses
The two major types of protective reactions of the innate immune system are inflammation
and antiviral defense. Inflammation is the process by which circulating leukocytes and
plasma proteins are brought into sites of infection in tissues and are activated to destroy and
eliminate the offending agents. Antiviral defense mechanisms prevent virus replication and
promote killing of infected cells, thus eliminating reservoirs of viral infection without an
inflammatory reaction.
The functions of innate immune responses have some
important general features:
- Physical and chemical defenses at epithelial barriers,
such as the skin and lining of the gastrointestinal and
respiratory tracts, block microbial entry.
- Innate immune responses are the initial reactions to
microbes that serve to control or eliminate infection
of the host by many pathogens. These responses are
activated by microbes that traverse epithelial barriers.
- Innate immunity eliminates damaged cells and initiates the process of tissue repair.
- Innate immune responses stimulate adaptive immune responses and can influence
the nature of the adaptive responses to make them optimally effective against
different types of microbes.
Comparative features of innate and adaptive immunity
Important differences between innate and adaptive:
- Innate immune effector cells and molecules are present in sufficient quantities even
before infection and are fully functional or quickly become activated by microbes to
prevent, control, or eliminate infections. In contrast, effective adaptive immune
responses to a newly introduced microbe develop over several days as clones of naive
antigen-specific lymphocytes expand and differentiate into functional effector cells.
- For most innate responses to microbes, there is no appreciable change in the quality
or magnitude of the response upon repeated exposure—that is, there is little or no
memory. In contrast, repeated exposure to a microbe enhances the rapidity,
magnitude, and effectiveness of adaptive immune responses.
