Myelopoiesis and Lymphopoiesis II

Question 1

Explain the process of maturation of T cells and NK cells.What receptors are expressed by them?

Answer 1

Both have a common precursor.Hint: All receptors expressed by T cells are below 10.

Question 2

Explain where B cell mature and where naive B cells develop into plasma cells.

Question 3

Explain the process of immunoglobulin gene rearrangement in B lymphocyte development.How can we detect if a B cell has undergone Ig gene rearrangement? What is its significance?

Answer 3

• ‘Ig Somatic Mutation’ occurs in antigenically stimulated B-cells in both heavy and light chain hypervariable regions.
• Cells with increased affinity for antigen survive.
• Cells with decreased affinity for antigen removed through apoptosis
  We can detect this by amplification and sequencing of V region which can then be compared with known germline V genes (which have not undergoine Ig somatic mutation).This is important for treating some B cellneoplasms

Question 4

Where does the Ig rearrangementandIg rearranged somatic mutation takes place?

Answer 4

Ig rearrangement takes place during B cell maturation which happens in the bone marrow whereas somatic mutation takes place in the presence of an antigen in the lymph nodes.

Question 5

Explain the structure of a lymph node.

Answer 5

Paracortex consists of T cells, cortex contains B cells.

Question 6

Enumerate common CD markers for different hematopoietic cell lines

Question 7

Enumerate the function of the red pulp and white pulp of the spleen.

Answer 7

Spleen consists of white pulp and red pulp areas, white pulp has a function similar to lymph nodes as it contains B and T cells with germinal centers and mantle zone.Red pulp has stromal cords and vascular sinuses so it allows the spleen to perform its blood filtering function by bringing the RBCsin close proximity with macrophages. Older erythrocytes are phagocytozed here.

Question 8

Define hypersplenism and list causes of splenomegaly

Answer 8

Enlargement of spleen, could be due

• Infections and inflammatory conditions Infectious mononucleosis, malaria, typhoid fever, leishmaniasis, rheumatoid arthritis, SLE
• Congestive – expansion of red pulp
• Portal hypertension, splenic or portal vein thrombosis, cardiac failure
• Infiltrative Amyloidosis, hemolytic anemia, immune thrombocytopenia, storage diseases, neoplasms

Question 9

List important causes of thymic hyperplasia

Answer 9

It is due to follicularhyperplasia. This can be for several reasons such as:

• Increased B-lymphocytes
• Myasthenia gravis
• SLE
• Graves disease and other autoimmune disorders

Question 10

List important paraneoplastic syndromes observed with thymic neoplasms.

Answer 10

Myasthenia Gravis and Pure Red Cell Aplasia are 2 common paraneoplastic manifestations of thymic neoplasms.