Immunology:
Foundations and
Frameworks
Last Updated: August 16, 2022
access_time14 min
Learning Objectives (4)
After completing this brick, you will be able to:
● Discuss the main purposes of the immune system.
● 1
● Briefly explain how the innate immune system works, and describe how
antigens are transferred from the innate to the adaptive immune system
(dendritic cells).
● 2
● Briefly describe the main purpose of the adaptive immune system, and
explain how the two arms (cellular and humoral) work.
● 3
● Describe what happens after an immune response is finished.
● 4
CASE CONNECTION
You are explaining to TJ, a 39-year-old man who just recovered from
a leg wound and infection, the intricate workings of the innate and
adaptive immune systems. You get the feeling he is really interested
in the topic as you explain how these systems performed individually
and as a pair to secure his recovery. “Well, let me ask you this. If
there’s all this activation, presentation, signaling, differentiation,
,ramping up, death, and destruction, how do things stop? What puts on
the brakes? Why isn’t my leg completely eaten away?”
How would you respond to TJ? Consider your answer as you read,
and we’ll revisit at the end of the brick.
What Is the Immune System?
How do we survive in a complex environment filled with harmful
organisms that thrive on colonizing us? Our heroic defender is the
immune system, a network of organs and cell lines that exist with the
mission of protecting the body from harm. While we often recognize
the pathogen-fighting capabilities of the system, we can sometimes
forget that the immune system is also crucial in ensuring the body is
kept safe from itself, as in when our cells transform into cancer cells.
On the dark side, sometimes our immune system can get overactive,
reacting against our own normal body tissue. Taken together, the
immune system is both critical for survival and a vital topic for new
medical research.
Immune System Functions
,In general, the purposes of the immune system can be broken down
into three categories:
● To defend against pathogens (eg, bacteria, viruses, parasites)
● To defend against malfunctioning cells (eg, neoplasms)
● To help “clean up” old tissue to facilitate growth
Malfunctions of the immune system can thus lead to devastating
problems, so the immune system must be tightly regulated to ensure
good control.
CLINICAL CORRELATION
Autoimmune diseases—such as multiple sclerosis, rheumatoid
arthritis, or Guillain-Barre syndrome—occur when the normal
immune response is dysregulated and begins to attack normal cells in
the body. As a result, many of the therapies for advanced forms are
immunosuppressive medications.
Immune System Organization
The immune system can be separated into two branches: the innate
immune system, characterized by rapid response and general defense,
, and the adaptive immune system, characterized by slower but more
targeted responses (Figure 1).
Figure 1
CREDIT: ©ScholarRx
These two branches play crucial roles individually. In addition,
communication between the two branches allows for coordinated,
stronger immune responses. We’ll look at each in turn.
Foundations and
Frameworks
Last Updated: August 16, 2022
access_time14 min
Learning Objectives (4)
After completing this brick, you will be able to:
● Discuss the main purposes of the immune system.
● 1
● Briefly explain how the innate immune system works, and describe how
antigens are transferred from the innate to the adaptive immune system
(dendritic cells).
● 2
● Briefly describe the main purpose of the adaptive immune system, and
explain how the two arms (cellular and humoral) work.
● 3
● Describe what happens after an immune response is finished.
● 4
CASE CONNECTION
You are explaining to TJ, a 39-year-old man who just recovered from
a leg wound and infection, the intricate workings of the innate and
adaptive immune systems. You get the feeling he is really interested
in the topic as you explain how these systems performed individually
and as a pair to secure his recovery. “Well, let me ask you this. If
there’s all this activation, presentation, signaling, differentiation,
,ramping up, death, and destruction, how do things stop? What puts on
the brakes? Why isn’t my leg completely eaten away?”
How would you respond to TJ? Consider your answer as you read,
and we’ll revisit at the end of the brick.
What Is the Immune System?
How do we survive in a complex environment filled with harmful
organisms that thrive on colonizing us? Our heroic defender is the
immune system, a network of organs and cell lines that exist with the
mission of protecting the body from harm. While we often recognize
the pathogen-fighting capabilities of the system, we can sometimes
forget that the immune system is also crucial in ensuring the body is
kept safe from itself, as in when our cells transform into cancer cells.
On the dark side, sometimes our immune system can get overactive,
reacting against our own normal body tissue. Taken together, the
immune system is both critical for survival and a vital topic for new
medical research.
Immune System Functions
,In general, the purposes of the immune system can be broken down
into three categories:
● To defend against pathogens (eg, bacteria, viruses, parasites)
● To defend against malfunctioning cells (eg, neoplasms)
● To help “clean up” old tissue to facilitate growth
Malfunctions of the immune system can thus lead to devastating
problems, so the immune system must be tightly regulated to ensure
good control.
CLINICAL CORRELATION
Autoimmune diseases—such as multiple sclerosis, rheumatoid
arthritis, or Guillain-Barre syndrome—occur when the normal
immune response is dysregulated and begins to attack normal cells in
the body. As a result, many of the therapies for advanced forms are
immunosuppressive medications.
Immune System Organization
The immune system can be separated into two branches: the innate
immune system, characterized by rapid response and general defense,
, and the adaptive immune system, characterized by slower but more
targeted responses (Figure 1).
Figure 1
CREDIT: ©ScholarRx
These two branches play crucial roles individually. In addition,
communication between the two branches allows for coordinated,
stronger immune responses. We’ll look at each in turn.
