Indicate whether each of the following statements concerning B-cell maturation i
ID: 164142 • Letter: I
Question
Indicate whether each of the following statements concerning B-cell maturation is true or false. If you think the statement is false, indicate, why?
A. Heavy chain V-D-J rearrangement begins in the pre-B-cell stage. FALSE – Late pro-B cells
B. Immature B cells express membrane IgM and IgD.
C. The enzyme terminal deoxyrybonucleotidyl transferase (TdT) is active in the pre-B_cell stage.
D. The surrogate light chain is expressed by pre-B-cells. TRUE
E. Self-reactive B cells can be rescued from negative selection by expression of a different light chain.
F. In order to develop into immature B cells, pre-B cells must interact directly with bone marrow stromal cells.
Explanation / Answer
A)False
Heavy chain V-D-J rearrangement begins in the pro-B cell stage.Lymphoid progenitor cells receive signals from bone marrow stromal cells to begin B cell development.Cytokines induce TdT and recombinase (RAG-1 and RAG-2) synthesis in CD34+ lymphoid progenitors.The cells undergo D-J joining on the H chain chromosome to become early pro-B cells and also begin expressing CD45 and Class II MHC.Joining of a V segment to the D-JH completes the late pro-B cell stage.
B)False.
Mature B cells express membrane IgM and IgD.
C)FALSE
The TdT enzyme is active in the pro-B cell during H chain rearrangement.
D)TRUE
E)FALSE-It is done by deletion or alteration
f)TRUE