The Immune Response
- For each of the features of the immunoglobulin molecule listed on the left select
the most appropriate association from those on the right.
a. Fab fragment.
b. Fc fragment.
c. F(ab1
)2 fragment.
A. C-terminal region.
B. Consists of heavy chains only.
C. Consists of light chain and part of heavy chain.
D. Consists of light chains only.
E. Pepsin digestion product.
The answer is C, A, E. Fab fragment – consists of light chain and part of heavy chain.
Papain digestion of monomeric immunoglobulin results in the production of two antibodybinding fragments (Fab) which consist of light chains plus part of the heavy chain.
Fc fragment – C-terminal region. Papain digestion of monomeric immunoglobulin
results in the production of a fragment consisting of the C-terminal ends of the heavy chains
linked together (Fc).
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F(ab1
)2 fragment – pepsin digestion product. Pepsin digestion splits the immunoglobulin
molecule to produce a fragment consisting of two Fab fragments united by a portion of the
Fc fragment. - For each of the types of immunoglobulin listed on the left select the most
appropriate association from those on the right.
a. IgG class specific antibody.
b. IgM class specific antibody.
c. Dimeric IgA class antibody.
A. J-chain.
B. Lymphocyte surface antigen receptor.
C. Mast cell degranulation.
D. Primary antibody response.
E. Secondary antibody response.
The answer is E, D, A. Following injection of antigen into an animal not previously
exposed to that antigen there is a transient appearance in the blood of a small quantity of
specific IgM class antibody in about 7 days (primary antibody response); re-injection of the
antigen at a later date results in production of IgG class antibody in large amounts within 4
days (secondary antibody response).
IgA is secreted by plasma cells as a dimer, i.e., 2 molecules linked together by a
polypeptide, J-chain. IgM is also produced as a pentamer, the 5 IgM molecules being linked
by 1 J-chain and 4 disulphide bonds.
Mast cell degranulation (C) is a property of IgE.
Lymphocyte surface antigen receptor (B) is a property of IgD. - For each of the types of T lymphocyte listed on the left select the most appropriate
association from the list of surface markers on the right.
a. Helper T lymphocytes.
b. Prothymocytes.
c. Suppressor T lymphocytes.
A. T4 positive cells.
B. T4 – T8 positive cells.
C. T8 positive cells.
D. T9 positive cells.
E. T10 positive cells.
The answer is A, E, C. Monoclonal antibodies to T lymphocyte surface antigens have
resulted in identification of various subtypes of T lymphocyte. T9 positive cells are primitive
T lymphocytes. Cells bearing both T4 and T8 are common thymocytes.
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Helper T lymphocytes – T4 positive cells.
Prothymocytes – T10 positive cells.
Suppressor T lymphocytes – T8 positive cells. - If the following features were put in chronological order which would come
fourth?
A. Exposure to antigen.
B. Differentiation into plasmablasts.
C. Immunoblast proliferation.
D. Production of mature plasma cells.
E. Stimulation of germinal centre cells.
The answer is B. Exposure to antigen (A) results in stimulation of (E) the cells in the
superficial cortex of the lymph node (germinal centre cells); these cells enlarge and develop
into B-immunoblasts (C) which divide and some differentiate into plasmablasts (B), which
mature into plasma cells (D). A proportion of the B-immunoblasts differentiate into B
memory cells and join the circulating pool of small lymphocytes. - For each of the features of a lymph node listed on the left select the most
appropriate association from those on the right?
a. Expansion of the deep cortex (paracortex) of the lymph node.
b. Primary lymphoid nodules.
c. Production of germinal centres.
A. Macrophage predominates.
B. Plasma cells predominate.
C. Region of T-cell response.
D. Superficial cortex of stimulated lymph node.
E. Superficial cortex of unstimulated lymph node.
The answer is C, E, D. Expansion of the deep cortex (paracortex) of the lymph node –
region of T-cell response. The deep (or para) cortex is the T-lymphocytic zone of the lymph
node and this enlarges during antigenic stimulus resulting in a cell mediated response.
Primary lymphoid nodules – superficial cortex of unstimulated lymph node. In the
unstimulated lymph node there are localized aggregates of lymphocytes in the superficial
cortex.
Production of germinal centres – superficial cortex of stimulated lymph node.
Following antigenic stimulation of a type resulting in antibody production (humoral response)
the primary nodules enlarge, to become germinal centres where B-lymphocytes proliferate.
During the humoral response plasma cells are produced and these may be seen in the
cortex deep to the germinal centres and in the medullary cords.
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Macrophages are present lining the lymph sinuses and in some forms of stimulation
may become very prominent (sinus histiocytosis)
