IMMUNOLOGY & SEROLOGY
(QUESTIONS AND CORRECT
DETAILED ANSWERS 2026 NEWEST
EDITION)
*From the following, identify a specific component of the adaptive immune system that is
formed in response to antigenic stimulation:
A. Lysozyme
B. Complement
C. Commensal organisms
D. Immunoglobulin - ANS -*D. Immunoglobulin is a specific part of the adaptive immune system
and is formed only in response to a specific antigenic stimulation. Complement, lysozyme, and
commensal organisms all act nonspecifically as a part of the adaptive immune system. These
three components do not require any type of specific antigenic stimulation.
*Which two organs are considered the primary lymphoid organs in which immunocompetent
cells originate and mature?
A. Thyroid and Peyer's patches B. Thymus and bone marrow
C. Spleen and mucosal-associated lymphoid tissue (MALT)
D. Lymph nodes and thoracic duct - ANS -*B. The bone marrow and thymus are considered
primary lymphoid organs because immunocompetent cells either originate or mature in them.
Some immunocompetent cells mature or reside in the bone marrow (the source of all
hematopoietic cells) until transported to the thymus, spleen, or Peyer's patches, where they
process antigen or manufacture antibody. T lymphocytes, after originating in the bone marrow,
travel to the thymus to mature and differentiate.
*What type of B cells are formed after antigen stimulation?
,A. Plasma cells and memory B cells
B. Mature B cells
C. Antigen-dependent B cells
*A Mature B cells exhibit surface immunoglobulin that may cross link a foreign antigen, thus
forming the activated B cell and leading to capping and internalization of antigen. The activated
B cell gives rise to plasma cells that produce and secrete immunoglobulins and memory cells
that reside in lymphoid organs.D. Receptor-activated B cells - ANS -*A. Mature B cells exhibit
surface immunoglobulin that may cross link a foreign antigen, thus forming the activated B cell
and leading to capping and internalization of antigen. The activated B cell gives rise to plasma
cells that produce and secrete immunoglobulins and memory cells that reside in lymphoid
organs.
*T cells travel from the bone marrow to the thymus for maturation. What is the correct order of
the maturation sequence for T cells in the thymus?
A. Bone marrow to the cortex; after thymic education, released back to peripheral circulation
B. Maturation and selection occur in the cortex; migration to the medulla; release of mature T
cells to secondary lymphoid organs
C. Storage in either the cortex or medulla; release of T cells into the peripheral circulation
D. Activation and selection occur in the medulla; mature T cells are stored in the cortex until
activated by antigen - ANS -*B. Immature T cells travel from the bone marrow to the thymus to
mature into functional T cells. Once in the thymus, T cells undergo a selection and maturation
sequence that begins in the cortex and moves to the medulla of the thymus. Thymic factors
such as thymosin and thymopoietin and cells within the thymus such as macrophages and
dendritic cells assist in this sequence. After completion of the maturation cycle, T cells are
released to secondary lymphoid organs to await antigen recognition and activation.
*Which cluster of differentiation (CD) marker appears during the first stage of T-cell
development and remains present as an identifying marker for T cells?
A. CD1
B. CD2
C. CD3
,D. CD4 or CD8 - ANS -*B. The CD2 marker appears during the first stage of T-cell development
and can be used to differentiate T cells from other lymphocytes. This T-lymphocyte receptor
binds sheep red blood cells (RBCs). This peculiar characteristic was the basis for the classic E
rosette test once used to enumerate T cells in peripheral blood. CD2 is not specific for T cells,
however, and is also found on large granular lymphocytes (LGL or natural killer [NK] cells).
*Which markers are found on mature, peripheral helper T cells? A. CD1, CD2, CD4
B. CD2, CD3, CD8
C. CD1, CD3, CD4
D. CD2, CD3, CD4 - ANS -*D. Mature, peripheral helper T cells have the CD2 (E rosette), CD3
(mature T cell), and CD4 (helper) markers.
*Which T cell expresses the CD8 marker and acts specifically to kill tumors or virally infected
cells?
A. Helper T
B. T suppressor
C. T cytotoxic
D. T inducer/suppressor - ANS -*C. T cytotoxic cells recognize antigen in association with major
histocompatibility complex (MHC) class I complexes and act against target cells that express
foreign antigens. These include viral antigens and the human leukocyte antigens (HLA) that are
the target of graft rejection
*How are cytotoxic T cells (TC cells) and natural killer (NK) cells similar?
A. Require antibody to be present B. Effective against virally infected cells
C. Recognize antigen in association with HLA class II markers
D. Do not bind to infected cells - ANS -*B. Both TC and NK cells are effective against virally
infected cells, and neither requires antibody to be present to bind to infected cells. NK cells do
not exhibit MHC class restriction, whereas activation of TC cells requires the presence of MHC
class I molecules in association with the viral antigen.
, *What is the name of the process by which phagocytic cells are attracted to a substance such as
a bacterial peptide?
A. Diapedesis
B. Degranulation
C. Chemotaxis
D. Phagotaxis - ANS -*C. Chemotaxis is the process by which phagocytic cells are attracted
toward an area where they detect a disturbance in the normal functions of body tissues.
Products from bacteria and viruses, complement components, coagulation proteins, and
cytokines from other immune cells may all act as chemotactic factors.
*All of the following are immunologic functions of complement except:
A. Induction of an antiviral state B. Opsonization
C. Chemotaxis
D. Anaphylatoxin formation - ANS -*A. Complement components are serum proteins that
function in opsonization, chemotaxis, and anaphylatoxin formation but do not induce an
antiviral state in target cells. This function is performed by interferons
*Which complement component is found in both the classic and alternative pathways?
A. C1
B. C4
C. Factor D
D. C3 - ANS -*D. C3 is found in both the classic and alternative (alternate) pathways of the
complement system. In the classic pathway, C3b forms a complex on the cell with C4b2a that
enzymatically cleaves C5. In the alternative pathway, C3b binds to an activator on the cell
surface. It forms a complex with factor B called C3bBb which, like C4b2a3b, can split C5.
*Which immunoglobulin(s) help(s) initiate the classic complement pathway?
A. IgA and IgD
B. IgM only
(QUESTIONS AND CORRECT
DETAILED ANSWERS 2026 NEWEST
EDITION)
*From the following, identify a specific component of the adaptive immune system that is
formed in response to antigenic stimulation:
A. Lysozyme
B. Complement
C. Commensal organisms
D. Immunoglobulin - ANS -*D. Immunoglobulin is a specific part of the adaptive immune system
and is formed only in response to a specific antigenic stimulation. Complement, lysozyme, and
commensal organisms all act nonspecifically as a part of the adaptive immune system. These
three components do not require any type of specific antigenic stimulation.
*Which two organs are considered the primary lymphoid organs in which immunocompetent
cells originate and mature?
A. Thyroid and Peyer's patches B. Thymus and bone marrow
C. Spleen and mucosal-associated lymphoid tissue (MALT)
D. Lymph nodes and thoracic duct - ANS -*B. The bone marrow and thymus are considered
primary lymphoid organs because immunocompetent cells either originate or mature in them.
Some immunocompetent cells mature or reside in the bone marrow (the source of all
hematopoietic cells) until transported to the thymus, spleen, or Peyer's patches, where they
process antigen or manufacture antibody. T lymphocytes, after originating in the bone marrow,
travel to the thymus to mature and differentiate.
*What type of B cells are formed after antigen stimulation?
,A. Plasma cells and memory B cells
B. Mature B cells
C. Antigen-dependent B cells
*A Mature B cells exhibit surface immunoglobulin that may cross link a foreign antigen, thus
forming the activated B cell and leading to capping and internalization of antigen. The activated
B cell gives rise to plasma cells that produce and secrete immunoglobulins and memory cells
that reside in lymphoid organs.D. Receptor-activated B cells - ANS -*A. Mature B cells exhibit
surface immunoglobulin that may cross link a foreign antigen, thus forming the activated B cell
and leading to capping and internalization of antigen. The activated B cell gives rise to plasma
cells that produce and secrete immunoglobulins and memory cells that reside in lymphoid
organs.
*T cells travel from the bone marrow to the thymus for maturation. What is the correct order of
the maturation sequence for T cells in the thymus?
A. Bone marrow to the cortex; after thymic education, released back to peripheral circulation
B. Maturation and selection occur in the cortex; migration to the medulla; release of mature T
cells to secondary lymphoid organs
C. Storage in either the cortex or medulla; release of T cells into the peripheral circulation
D. Activation and selection occur in the medulla; mature T cells are stored in the cortex until
activated by antigen - ANS -*B. Immature T cells travel from the bone marrow to the thymus to
mature into functional T cells. Once in the thymus, T cells undergo a selection and maturation
sequence that begins in the cortex and moves to the medulla of the thymus. Thymic factors
such as thymosin and thymopoietin and cells within the thymus such as macrophages and
dendritic cells assist in this sequence. After completion of the maturation cycle, T cells are
released to secondary lymphoid organs to await antigen recognition and activation.
*Which cluster of differentiation (CD) marker appears during the first stage of T-cell
development and remains present as an identifying marker for T cells?
A. CD1
B. CD2
C. CD3
,D. CD4 or CD8 - ANS -*B. The CD2 marker appears during the first stage of T-cell development
and can be used to differentiate T cells from other lymphocytes. This T-lymphocyte receptor
binds sheep red blood cells (RBCs). This peculiar characteristic was the basis for the classic E
rosette test once used to enumerate T cells in peripheral blood. CD2 is not specific for T cells,
however, and is also found on large granular lymphocytes (LGL or natural killer [NK] cells).
*Which markers are found on mature, peripheral helper T cells? A. CD1, CD2, CD4
B. CD2, CD3, CD8
C. CD1, CD3, CD4
D. CD2, CD3, CD4 - ANS -*D. Mature, peripheral helper T cells have the CD2 (E rosette), CD3
(mature T cell), and CD4 (helper) markers.
*Which T cell expresses the CD8 marker and acts specifically to kill tumors or virally infected
cells?
A. Helper T
B. T suppressor
C. T cytotoxic
D. T inducer/suppressor - ANS -*C. T cytotoxic cells recognize antigen in association with major
histocompatibility complex (MHC) class I complexes and act against target cells that express
foreign antigens. These include viral antigens and the human leukocyte antigens (HLA) that are
the target of graft rejection
*How are cytotoxic T cells (TC cells) and natural killer (NK) cells similar?
A. Require antibody to be present B. Effective against virally infected cells
C. Recognize antigen in association with HLA class II markers
D. Do not bind to infected cells - ANS -*B. Both TC and NK cells are effective against virally
infected cells, and neither requires antibody to be present to bind to infected cells. NK cells do
not exhibit MHC class restriction, whereas activation of TC cells requires the presence of MHC
class I molecules in association with the viral antigen.
, *What is the name of the process by which phagocytic cells are attracted to a substance such as
a bacterial peptide?
A. Diapedesis
B. Degranulation
C. Chemotaxis
D. Phagotaxis - ANS -*C. Chemotaxis is the process by which phagocytic cells are attracted
toward an area where they detect a disturbance in the normal functions of body tissues.
Products from bacteria and viruses, complement components, coagulation proteins, and
cytokines from other immune cells may all act as chemotactic factors.
*All of the following are immunologic functions of complement except:
A. Induction of an antiviral state B. Opsonization
C. Chemotaxis
D. Anaphylatoxin formation - ANS -*A. Complement components are serum proteins that
function in opsonization, chemotaxis, and anaphylatoxin formation but do not induce an
antiviral state in target cells. This function is performed by interferons
*Which complement component is found in both the classic and alternative pathways?
A. C1
B. C4
C. Factor D
D. C3 - ANS -*D. C3 is found in both the classic and alternative (alternate) pathways of the
complement system. In the classic pathway, C3b forms a complex on the cell with C4b2a that
enzymatically cleaves C5. In the alternative pathway, C3b binds to an activator on the cell
surface. It forms a complex with factor B called C3bBb which, like C4b2a3b, can split C5.
*Which immunoglobulin(s) help(s) initiate the classic complement pathway?
A. IgA and IgD
B. IgM only
