Question

1-2. patient A

---DR B1 1101---- DR B3 4101---------------------- DR A 0101---

---DR B1 0903------------------------DR B4 0501---- DR A 0102---

patient B

---DR B1 1001------------------------------------------ DR A 0101---

---DR B1 0804------------------------DR B4 0402---- DR A 0101---

1. Given that expression is co-dominant, how many distinct HLA DR pairs are possible in patient A?________

2. patient B?________

3-4. You are going to use flow cytometry to determine the proportion of developing B cells in the bone marrow that are hematopoietic stem cells, pro-B cells, immature, or mature B cells. You have three monoclonal antibodies specific for four different B-cell surface proteins. The first has specificity for the cell-surface protein CD19, which is expressed by all developing and mature B cells; the second is specific for the Fc region of IgD; the third is specific for the Fc region of IgM and the fourth is specific for CD34. The antibodies are conjugated to four different fluorescent tags that can be detected and distinguished by the flow cytometer.

3. A histogram can show you which cells are CD19-positive cells, which are CD34- positive cells and which have both. How would you distinguish between a hematopoietic stem cell and a pro-B cell?

4. Using a two-dimensional dot plot, you can compare the level of expression of IgD and IgM of CD19 gated cells. How would you distinguish (i) immature B cells, (ii) mature B cells.

5-6. Large pre-B cells undergo clonal expansion before the rearrangement of light-chain loci. Explain the beneficial consequences of clonal expansion before the rearrangement of light-chain loci in terms of the following:

5. Conservation of the energy used to make a functional heavy chain.

6. Diverse population of immature B cells is generated.

7-8. Multiple myeloma involves the unregulated proliferation of a clone of antibody-producing plasma cell (myeloma cell) independently of antigen stimulation or T-cell help. Myeloma cells populate multiple sites in the bone marrow, where they produce immense quantities of monoclonal (single clone) immunoglobulin as well as suppressing normal marrow function. Myeloma cells also synthesize and secrete excessive amounts of free light chains (known as Bence-Jones protein), which, because of their low molecular weight (~25 kDa) are excreted as free light chains in the urine.

7. In a given patient the free light chains are both monoclonal and all are of either the κ or the λ type. Explain both of these observations.

8. Why do you think patients with multiple myeloma are more susceptible than normal to pyogenic infections, such as pneumonia caused by Streptococcus pneumonia or Haemophilus influenzae?

9-10. Giulia McGettigan was born full-term with a malformed jaw, cleft palate, a ventricular septal defect, and hypocalcemia. Within 48 hours of birth, she developed muscle tetany, convulsions, tachypnea, and a systolic murmur. A chest X-ray showed an enlarged heart and the absence of a thymic shadow. Blood tests showed severely depleted levels of CD4 and CD8 T cells; B-cell numbers were low but within normal range. Parathyroid hormone was undetectable. Fluorescence in situ hybridization of the buccal mucosa revealed a small deletion in the long arm of chromosome 22. Giulia failed to thrive and battled chronic diarrhea and opportunistic infections, including oral candidiasis and Pneumocystis jirovecii, the latter infection causing her death. Giulia most probably had which of the following immunodeficiency diseases?

9. _____

a.

AIDS (depletes CD4+ T cells)

b.

DiGeorge syndrome (absence of thymus)

c.

bare lymphocyte syndrome (lack of class I or class II MHC on lymphocytes and

thymic epithelial cells)

d.

chronic granulomatous disease

e.

hyper IgM syndrome (cannot switch immunoglobulin isotype)

10. Why?

Answer 1