PSIO 431 FINAL UPDATED ACTUAL
QUESTIONS AND CORRECT ANSWERS
Question:
1. What is SCID?
Answer:
If there are low numbers of T and B cells, it is as if there is a block in the development of the lymphoid
stem cell, or its further maturation. This condition is the worst of the immunodeficiency states and is
called Severe Combined Immunodeficiency Disease, or SCID. Children with the most profound
deficiencies rarely survive beyond a year (they are to some extent protected in the neonatal period by
maternal IgG). There is lymphopenia of both T and B cells, absent thymic shadow on X-ray, and small
tonsils; serum immunoglobulins are low
Question:
2. What is the difference between primary and secondary immunodeficiency?
Answer:
Primary immunodeficiency (congenital) means a disease with a genetic cause, while secondary
(acquired) implies that some known process outside the immune system has caused the
immunodeficiency.
Question:
3. What kind of cells do primary immunodeficiencies affect?
Answer:
These can affect T cells or B cells selectively, or both kinds of cells. It is largely by studying the
clinical syndromes associated with immunodeficiency diseases that we know what T and B cells are
really important for in humans.
Question:
4. What is SCID-X1? Where is the defect located?
Answer:
More than half the cases are X-linked. In the commonest of these (SCID-X1), the defect is in the gene
for the gamma chain that forms part of the receptors for IL-2 (Th1 secretes IL-2, which helps CTL
(killer T cells) get fully activated after they recognize antigen.) and other growth factors necessary for
lymphoid development, or their signaling pathways.
Question:
5. What is the other mode of inheritance (not X linked) for people with SCID? What is it caused by?
Answer:
SCID cases are autosomal recessive. Most of these patients lack the enzyme adenosine deaminase
(ADA); adenosine accumulates in all cells but apparently impairs lymphocyte development most
severely
Question:
6. Where would the block be if there are normal T cells but low to absent B cells?
,Answer:
Bruton's agammaglobulinemia If there are normal T cells but low to absent B cells, it may be that
there is a developmental block between the pre-B cell and the B cell. Most patients have pre-B cells in
their bone marrow but are deficient in B cells and antibody.
Question:
7. Where is the block if a patient has high IgM and low IgG and IgA?
Answer:
X-linked hyperIgM syndrome A rare patient will have high IgM with low IgG and IgA; in such
patients there is a defect in the IgM-to-IgG switch mechanism. The Tfh cell has an accessory molecule
(CD40- ligand) that interacts with CD40 on B cells, signaling them to switch classes If either molecule
is defective, the B cell is driven hard but can't be instructed to switch past making IgM.
Question:
8. If B cells are not differentiating into plasma cells then what will happen?
Answer:
there are normal numbers of pre-B cells and B cells, but the B cells are difficult to trigger to make
specific antibody. Serum IgG is low, at 0.5 g/dL or less.
Question:
9. The thymus is a two component organ. What are the two components and where do they come
from? What happens if they develop abnormally?
Answer:
DiGeorge Syndrome The lymphoid part comes from precursors in the bone marrow, as we already
know; the stroma is derived in the embryo from the endoderm and ectoderm of the 3rd and 4th
pharyngeal pouches. If these develop abnormally the stroma will not support thymic lymphoid
development, and the patient will have absent T cells with normal B cells.
Question:
10. What is Ataxia Telangiectasia?
Answer:
an autosomal recessive disease characterized by sinus infections and pneumonia, ataxia (staggering)
and telangiectasia (dilated abnormal blood vessels). There is both T and B cell deficiency, not
absolute; IgA is especially depressed. There is also an interesting defect in DNA repair which may
partially explain the extraordinary incidence of tumors in these patients. The Wiskott-Aldrich
syndrome is comprised of platelet and B cell deficiency, eczema, and many bacterial infections. It is
X-linked.
Question:
11. What are some treatments for immunodeficiency?
Answer:
1. Isolation = bubbles.
2. Prophylactic antibiotics. Use these in combinations, which you change monthly
3. Human immunoglobulin, where B cell function is deficient.
4. Transplantation.
5. thymus peptides
, Question:
12. What does a a skin test with an antigen that produces good Th1-mediated immunity is positive tell
you?
Answer:
the patient can: process antigen in APCs, recognize antigen, expand a T cell clone, activate T cells,
secrete lymphokines, and respond to lymphokines; which is a lot more information than can be had by
measuring CD4+ cells.
Question:
13. What are initial and advanced tests for people with Bcell defective immunity?
Answer:
Initial Serum protein electrophoresis Quantitative IgG, IgA, IgM levels Specific Abs to prior
immunizations ABO isohemagglutinins Advanced Ab responses to novel Ags Sequencing of suspect
genes
Question:
14. What are initial and advanced tests for people with Tcell defective immunity?
Answer:
Initial Skin test with recall Ag panel Total lymphocyte count Advanced CD3, CD4, CD8 counts
Mitogen responses, MLR, cytokine measurements
Question:
15. What are initial and advanced tests for people with phagocyte defective immunity?
Answer:
Initial WBC count, differential, morphology NBT test, oxidative burst Advanced Assays for
phagocytosis, chemotaxis Genetics
Question:
16. What are initial and advanced tests for people with complement defective immunity?
Answer:
Initial CH50 Assay for C1inh (inhibitor) Advanced Individual complement component levels
Question:
17. What are blood group antigens?
Answer:
Blood group antigens are glycolipids found on the surface of all body cells, including of course red
cells. The lipid backbone spans the plasma membrane, and the terminal sugars confer the antigenic
specificity, A, B or O.
Question:
18. What are blood group substances?
Answer:
Blood group substances are glycoproteins with the same sugars, found in the body fluids of people
who have the Secretor (Se) phenotype. About 80% of people are secretors; their blood type can be
determined from sweat stains, cigarette butts, etc. There are no particular advantages to being a
secretor.
QUESTIONS AND CORRECT ANSWERS
Question:
1. What is SCID?
Answer:
If there are low numbers of T and B cells, it is as if there is a block in the development of the lymphoid
stem cell, or its further maturation. This condition is the worst of the immunodeficiency states and is
called Severe Combined Immunodeficiency Disease, or SCID. Children with the most profound
deficiencies rarely survive beyond a year (they are to some extent protected in the neonatal period by
maternal IgG). There is lymphopenia of both T and B cells, absent thymic shadow on X-ray, and small
tonsils; serum immunoglobulins are low
Question:
2. What is the difference between primary and secondary immunodeficiency?
Answer:
Primary immunodeficiency (congenital) means a disease with a genetic cause, while secondary
(acquired) implies that some known process outside the immune system has caused the
immunodeficiency.
Question:
3. What kind of cells do primary immunodeficiencies affect?
Answer:
These can affect T cells or B cells selectively, or both kinds of cells. It is largely by studying the
clinical syndromes associated with immunodeficiency diseases that we know what T and B cells are
really important for in humans.
Question:
4. What is SCID-X1? Where is the defect located?
Answer:
More than half the cases are X-linked. In the commonest of these (SCID-X1), the defect is in the gene
for the gamma chain that forms part of the receptors for IL-2 (Th1 secretes IL-2, which helps CTL
(killer T cells) get fully activated after they recognize antigen.) and other growth factors necessary for
lymphoid development, or their signaling pathways.
Question:
5. What is the other mode of inheritance (not X linked) for people with SCID? What is it caused by?
Answer:
SCID cases are autosomal recessive. Most of these patients lack the enzyme adenosine deaminase
(ADA); adenosine accumulates in all cells but apparently impairs lymphocyte development most
severely
Question:
6. Where would the block be if there are normal T cells but low to absent B cells?
,Answer:
Bruton's agammaglobulinemia If there are normal T cells but low to absent B cells, it may be that
there is a developmental block between the pre-B cell and the B cell. Most patients have pre-B cells in
their bone marrow but are deficient in B cells and antibody.
Question:
7. Where is the block if a patient has high IgM and low IgG and IgA?
Answer:
X-linked hyperIgM syndrome A rare patient will have high IgM with low IgG and IgA; in such
patients there is a defect in the IgM-to-IgG switch mechanism. The Tfh cell has an accessory molecule
(CD40- ligand) that interacts with CD40 on B cells, signaling them to switch classes If either molecule
is defective, the B cell is driven hard but can't be instructed to switch past making IgM.
Question:
8. If B cells are not differentiating into plasma cells then what will happen?
Answer:
there are normal numbers of pre-B cells and B cells, but the B cells are difficult to trigger to make
specific antibody. Serum IgG is low, at 0.5 g/dL or less.
Question:
9. The thymus is a two component organ. What are the two components and where do they come
from? What happens if they develop abnormally?
Answer:
DiGeorge Syndrome The lymphoid part comes from precursors in the bone marrow, as we already
know; the stroma is derived in the embryo from the endoderm and ectoderm of the 3rd and 4th
pharyngeal pouches. If these develop abnormally the stroma will not support thymic lymphoid
development, and the patient will have absent T cells with normal B cells.
Question:
10. What is Ataxia Telangiectasia?
Answer:
an autosomal recessive disease characterized by sinus infections and pneumonia, ataxia (staggering)
and telangiectasia (dilated abnormal blood vessels). There is both T and B cell deficiency, not
absolute; IgA is especially depressed. There is also an interesting defect in DNA repair which may
partially explain the extraordinary incidence of tumors in these patients. The Wiskott-Aldrich
syndrome is comprised of platelet and B cell deficiency, eczema, and many bacterial infections. It is
X-linked.
Question:
11. What are some treatments for immunodeficiency?
Answer:
1. Isolation = bubbles.
2. Prophylactic antibiotics. Use these in combinations, which you change monthly
3. Human immunoglobulin, where B cell function is deficient.
4. Transplantation.
5. thymus peptides
, Question:
12. What does a a skin test with an antigen that produces good Th1-mediated immunity is positive tell
you?
Answer:
the patient can: process antigen in APCs, recognize antigen, expand a T cell clone, activate T cells,
secrete lymphokines, and respond to lymphokines; which is a lot more information than can be had by
measuring CD4+ cells.
Question:
13. What are initial and advanced tests for people with Bcell defective immunity?
Answer:
Initial Serum protein electrophoresis Quantitative IgG, IgA, IgM levels Specific Abs to prior
immunizations ABO isohemagglutinins Advanced Ab responses to novel Ags Sequencing of suspect
genes
Question:
14. What are initial and advanced tests for people with Tcell defective immunity?
Answer:
Initial Skin test with recall Ag panel Total lymphocyte count Advanced CD3, CD4, CD8 counts
Mitogen responses, MLR, cytokine measurements
Question:
15. What are initial and advanced tests for people with phagocyte defective immunity?
Answer:
Initial WBC count, differential, morphology NBT test, oxidative burst Advanced Assays for
phagocytosis, chemotaxis Genetics
Question:
16. What are initial and advanced tests for people with complement defective immunity?
Answer:
Initial CH50 Assay for C1inh (inhibitor) Advanced Individual complement component levels
Question:
17. What are blood group antigens?
Answer:
Blood group antigens are glycolipids found on the surface of all body cells, including of course red
cells. The lipid backbone spans the plasma membrane, and the terminal sugars confer the antigenic
specificity, A, B or O.
Question:
18. What are blood group substances?
Answer:
Blood group substances are glycoproteins with the same sugars, found in the body fluids of people
who have the Secretor (Se) phenotype. About 80% of people are secretors; their blood type can be
determined from sweat stains, cigarette butts, etc. There are no particular advantages to being a
secretor.
