BASIC IMMUNOLOGY EXAM -
Functions and Disorders of the Immune
System Latest Update 2026/ Immunology
Exam 1 Questions with Answers
Reviewed 2026/ Basic Principles of
Immunology Exam/Basic Immunology
(MCB 4211) Final Exam . All 250
Questions with Correct Answers with
Rationales Already Graded A+
Guaranteed Pass
What are the antigen recognizing domains? - ANSWER✔️The antigen-
recognizing domains of the receptors are called variable (V) regions, and the
conserved portions are the constant (C) regions. Even within each V region, most
of the sequence variability is concentrated within short stretches, which are called
hypervariable regions, or complementarity-determining regions (cdrs), because
they form the parts of the receptor that bind antigens (i.e., they are complementary
to the shapes of antigens). By concentrating sequence variation in small regions of
the receptor, it is possible to maximize the variability of the antigen-binding part,
while retaining the basic structure of the receptors. As discussed later, special
mechanisms exist in developing lymphocytes to create genes that encode different
variable regions of antigen receptor proteins in individual clones.
What is the purpose of antigen receptor chains? - ANSWER✔️Antigen receptor
chains are associated with invariant membrane proteins whose function is to
deliver intracellular signals following antigen recognition (see Fig. 4-1 ). These
signals, which are transmitted to the cytosol and the nucleus, may cause a
lymphocyte to divide, to differentiate, or in certain circumstances to die. Thus, the
two functions of lymphocyte receptors for antigen—specific antigen recognition
and signal transduction—are mediated by different polypeptides. This again allows
variability to be segregated in one set of molecules—the receptors themselves—
,while leaving the conserved function of signal transduction in other, invariant
proteins
What occurs when an antigen molecule binds to antigen receptors of lymphocytes?
- ANSWER✔️When antigen molecules bind to antigen receptors of lymphocytes,
the associated signaling proteins of the receptor complexes are brought into
proximity. As a result, enzymes attached to the cytoplasmic portions of the
signaling proteins catalyze the phosphorylation of other proteins. Phosphorylation
triggers complex signaling cascades that culminate in the transcriptional activation
of many genes and the production of numerous proteins that mediate the responses
of the lymphocytes.
What are the two ways that antibodies exist? - ANSWER✔️Antibodies exist in
two forms—as membrane-bound antigen receptors on B cells or as secreted
proteins—but tcrs exist only as membrane receptors on T cells. Secreted antibodies
are present in the blood and mucosal secretions, where they function to defend
against microbes
What are immunoglobulins? (Igs) - ANSWER✔️Antibodies are also called
immunoglobulins (Igs), referring to immunity-conferring proteins with the
characteristic slow electrophoretic mobility of globulins. Secreted antibodies
recognize microbial antigens and toxins by their variable domains, the same as the
membrane-bound antigen receptors of B lymphocytes. The constant regions of
some secreted antibodies have the ability to bind to other molecules that participate
in the elimination of antigens: these molecules include receptors on phagocytes and
proteins of the complement system.
What are the different functions of different antibodies? - ANSWER✔️antibodies
serve different functions at different stages of humoral immune responses:
membrane-bound antibodies on B cells recognize antigens to initiate the responses,
and secreted antibodies neutralize and eliminate microbes and their toxins in the
effector phase of humoral immunity.
In b lymphocytes, antigen recognition is mediated by? - ANSWER✔️variable V
regions of heavy and light chains of membrane Ig
In t lymphocytes, antigen recognition is mediated by? - ANSWER✔️variable V
regions of alpha and beta chains of the TCR
,In b lymphocytes, signaling functions are mediated by? - ANSWER✔️proteins (Ig
alpha and Ig beta) associated with membrane Ig
In t lymphocyytes, signaling functions are mediated by? - ANSWER✔️proteins
(CD3 and zeta chain) associated with the TCR
In b lymphocytes, efector functions are mediated by? - ANSWER✔️constant C
regions of secreted Ig
In t lymphocytes, effector functions are mediated by? - ANSWER✔️TCR does not
perform effector functions
An antibody molecule is composed of what? - ANSWER✔️Content section
navigation
Antigen Receptors of Lymphocytes
Antibodies
T Cell Receptors for Antigens
Development of Immune Repertoires
Lymphocyte Development
Production of Diverse Antigen Receptors
Maturation and Selection of B Lymphocytes
Maturation and Selection of T Lymphocytes
Summary
Review Questions
Cover of Basic Immunology: Functions and Disorders of the Immune System
Basic Immunology: Functions and Disorders of the Immune System
Fifth Edition
Copyright © 2016 by Elsevier Inc. All rights reserved.
Want to own this book?
Buy your copy at Elsevier Health Bookstore today
Get rights and content
BOOK CHAPTER
Antigen Recognition in the Adaptive Immune System: Structure of Lymphocyte
Antigen Receptors and Development of Immune Repertoires PDF not available
through clinicalkey
, Abul K. Abbas MBBS, Andrew H. Lichtman MD, phd and Shiv Pillai MBBS, phd
Basic Immunology: Functions and Disorders of the Immune System, Chapter 4,
79-102
Open reading mode
Open full size image
Antigen receptors serve critical roles in the maturation of lymphocytes from
progenitors and in all adaptive immune responses. In adaptive immunity, naive
lymphocytes recognize antigens to initiate responses, and effector T cells and
antibodies recognize antigens to perform their functions.
B and T lymphocytes express different receptors that recognize antigens:
membrane-bound antibodies on B cells and T cell receptors (tcrs) on T
lymphocytes. The principal function of cellular receptors in the immune system, as
in other biologic systems, is to detect external stimuli (antigens, for the antigen
receptors of the adaptive immune system) and trigger responses of the cells on
which the receptors are expressed. To recognize a large variety of different
antigens, the antigen receptors of lymphocytes must be able to bind to and
distinguish between many
What is the antigen binding site on an antibody? - ANSWER✔️The antigen-
binding site of an antibody is composed of the V regions of both the heavy chain
and the light chain, and the core antibody structure contains two identical antigen
binding sites (see Fig. 4-2 ). Each variable region of the heavy chain (called V H )
or of the light chain (called V L ) contains three hypervariable regions, or cdrs. Of
these three, the greatest variability is in CDR3, which is located at the junction of
the V and C regions. As may be predicted from this variability, CDR3 is also the
portion of the Ig molecule that contributes most to antigen binding.
What is the portion of the Ig molecule that contributes most to antigen binding? -
ANSWER✔️Of these three, the greatest variability is in CDR3, which is located at
the junction of the V and C regions. As may be predicted from this variability,
CDR3 is also the portion of the Ig molecule that contributes most to antigen
binding.
What is the Fab region? - ANSWER✔️The fragment of an antibody that contains a
whole light chain (with its single V and C domains) attached to the V and first C
Functions and Disorders of the Immune
System Latest Update 2026/ Immunology
Exam 1 Questions with Answers
Reviewed 2026/ Basic Principles of
Immunology Exam/Basic Immunology
(MCB 4211) Final Exam . All 250
Questions with Correct Answers with
Rationales Already Graded A+
Guaranteed Pass
What are the antigen recognizing domains? - ANSWER✔️The antigen-
recognizing domains of the receptors are called variable (V) regions, and the
conserved portions are the constant (C) regions. Even within each V region, most
of the sequence variability is concentrated within short stretches, which are called
hypervariable regions, or complementarity-determining regions (cdrs), because
they form the parts of the receptor that bind antigens (i.e., they are complementary
to the shapes of antigens). By concentrating sequence variation in small regions of
the receptor, it is possible to maximize the variability of the antigen-binding part,
while retaining the basic structure of the receptors. As discussed later, special
mechanisms exist in developing lymphocytes to create genes that encode different
variable regions of antigen receptor proteins in individual clones.
What is the purpose of antigen receptor chains? - ANSWER✔️Antigen receptor
chains are associated with invariant membrane proteins whose function is to
deliver intracellular signals following antigen recognition (see Fig. 4-1 ). These
signals, which are transmitted to the cytosol and the nucleus, may cause a
lymphocyte to divide, to differentiate, or in certain circumstances to die. Thus, the
two functions of lymphocyte receptors for antigen—specific antigen recognition
and signal transduction—are mediated by different polypeptides. This again allows
variability to be segregated in one set of molecules—the receptors themselves—
,while leaving the conserved function of signal transduction in other, invariant
proteins
What occurs when an antigen molecule binds to antigen receptors of lymphocytes?
- ANSWER✔️When antigen molecules bind to antigen receptors of lymphocytes,
the associated signaling proteins of the receptor complexes are brought into
proximity. As a result, enzymes attached to the cytoplasmic portions of the
signaling proteins catalyze the phosphorylation of other proteins. Phosphorylation
triggers complex signaling cascades that culminate in the transcriptional activation
of many genes and the production of numerous proteins that mediate the responses
of the lymphocytes.
What are the two ways that antibodies exist? - ANSWER✔️Antibodies exist in
two forms—as membrane-bound antigen receptors on B cells or as secreted
proteins—but tcrs exist only as membrane receptors on T cells. Secreted antibodies
are present in the blood and mucosal secretions, where they function to defend
against microbes
What are immunoglobulins? (Igs) - ANSWER✔️Antibodies are also called
immunoglobulins (Igs), referring to immunity-conferring proteins with the
characteristic slow electrophoretic mobility of globulins. Secreted antibodies
recognize microbial antigens and toxins by their variable domains, the same as the
membrane-bound antigen receptors of B lymphocytes. The constant regions of
some secreted antibodies have the ability to bind to other molecules that participate
in the elimination of antigens: these molecules include receptors on phagocytes and
proteins of the complement system.
What are the different functions of different antibodies? - ANSWER✔️antibodies
serve different functions at different stages of humoral immune responses:
membrane-bound antibodies on B cells recognize antigens to initiate the responses,
and secreted antibodies neutralize and eliminate microbes and their toxins in the
effector phase of humoral immunity.
In b lymphocytes, antigen recognition is mediated by? - ANSWER✔️variable V
regions of heavy and light chains of membrane Ig
In t lymphocytes, antigen recognition is mediated by? - ANSWER✔️variable V
regions of alpha and beta chains of the TCR
,In b lymphocytes, signaling functions are mediated by? - ANSWER✔️proteins (Ig
alpha and Ig beta) associated with membrane Ig
In t lymphocyytes, signaling functions are mediated by? - ANSWER✔️proteins
(CD3 and zeta chain) associated with the TCR
In b lymphocytes, efector functions are mediated by? - ANSWER✔️constant C
regions of secreted Ig
In t lymphocytes, effector functions are mediated by? - ANSWER✔️TCR does not
perform effector functions
An antibody molecule is composed of what? - ANSWER✔️Content section
navigation
Antigen Receptors of Lymphocytes
Antibodies
T Cell Receptors for Antigens
Development of Immune Repertoires
Lymphocyte Development
Production of Diverse Antigen Receptors
Maturation and Selection of B Lymphocytes
Maturation and Selection of T Lymphocytes
Summary
Review Questions
Cover of Basic Immunology: Functions and Disorders of the Immune System
Basic Immunology: Functions and Disorders of the Immune System
Fifth Edition
Copyright © 2016 by Elsevier Inc. All rights reserved.
Want to own this book?
Buy your copy at Elsevier Health Bookstore today
Get rights and content
BOOK CHAPTER
Antigen Recognition in the Adaptive Immune System: Structure of Lymphocyte
Antigen Receptors and Development of Immune Repertoires PDF not available
through clinicalkey
, Abul K. Abbas MBBS, Andrew H. Lichtman MD, phd and Shiv Pillai MBBS, phd
Basic Immunology: Functions and Disorders of the Immune System, Chapter 4,
79-102
Open reading mode
Open full size image
Antigen receptors serve critical roles in the maturation of lymphocytes from
progenitors and in all adaptive immune responses. In adaptive immunity, naive
lymphocytes recognize antigens to initiate responses, and effector T cells and
antibodies recognize antigens to perform their functions.
B and T lymphocytes express different receptors that recognize antigens:
membrane-bound antibodies on B cells and T cell receptors (tcrs) on T
lymphocytes. The principal function of cellular receptors in the immune system, as
in other biologic systems, is to detect external stimuli (antigens, for the antigen
receptors of the adaptive immune system) and trigger responses of the cells on
which the receptors are expressed. To recognize a large variety of different
antigens, the antigen receptors of lymphocytes must be able to bind to and
distinguish between many
What is the antigen binding site on an antibody? - ANSWER✔️The antigen-
binding site of an antibody is composed of the V regions of both the heavy chain
and the light chain, and the core antibody structure contains two identical antigen
binding sites (see Fig. 4-2 ). Each variable region of the heavy chain (called V H )
or of the light chain (called V L ) contains three hypervariable regions, or cdrs. Of
these three, the greatest variability is in CDR3, which is located at the junction of
the V and C regions. As may be predicted from this variability, CDR3 is also the
portion of the Ig molecule that contributes most to antigen binding.
What is the portion of the Ig molecule that contributes most to antigen binding? -
ANSWER✔️Of these three, the greatest variability is in CDR3, which is located at
the junction of the V and C regions. As may be predicted from this variability,
CDR3 is also the portion of the Ig molecule that contributes most to antigen
binding.
What is the Fab region? - ANSWER✔️The fragment of an antibody that contains a
whole light chain (with its single V and C domains) attached to the V and first C
