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The Immune System
LEARNING OBJECTIVES
Define and describe the components of the immune system
Discriminate between innate and acquired immunity
The Immune System
The immune system is designed to recognize and respond to non-self antigen in a coordinated manner. Additionally, it recognizes and eliminates cells that are diseased, damaged, distressed, or dying.
The immune system is divided into 2 complementary arms: the innate and the adaptive immune systems.
INNATE IMMUNITY
Innate immunity provides the body?s first line of defense against infectious agents. It involves several defensive barriers:
Innate immune defenses have the following characteristics in common:
ADAPTIVE IMMUNITY
The components of the adaptive immune response are B and T lymphocytes and their effector cells.
Adaptive immune defenses have the following characteristics in common:
The features of adaptive immunity are designed to give the individual the best possible defense against disease.
Characteristics Innate Adaptive
Specificity For pathogen-associated molecular patterns (PAMPs) For specific antigens of microbial and nonmicrobial agents
Diversity Limited High
Anatomic and physical (skin, mucous membranes and normal flora)
Physiologic (temperature, pH, anti-microbials and cytokines)
Complement
Cellular: phagocytes and granulocytes
Inflammation
Are present intrinsically with or without previous stimulation
Have limited specificity for shared microbe and cellular structures (pathogen-associated molecular patterns [PAMPs] and damage-associated molecular patterns [DAMPs])
Have limited diversity as reflected by a limited number of pattern recognition receptors
Are not enhanced in activity upon subsequent exposure?no memory
Each B and T lymphocyte is specific for a particular antigen
As a population, lymphocytes have extensive diversity
Are enhanced with each repeat exposure�?immunologic memory
Are capable of distinguishing self from non-self
Are self-limiting
Specificity is required, along with immunologic memory, to protect against persistent or recurrent challenge.
Diversity is required to protect against the maximum number of potential pathogens.
Specialization of effector function is necessary so that the most effective defense can be mounted against diverse challenges.
The ability to distinguish between self (host cells) and non-self (pathogens) is vital in inhibiting an autoimmune response.
Self-limitation allows the system to return to a basal resting state after a challenge to conserve energy and resources and to avoid uncontrolled cell proliferation resulting in leukemia or lymphoma
