Generation of Immune Antibodies

Question 1

clonal selection

Answer 1

Selection of mature B lymphocytes by interaction with antigen. This occurs in the periphery as antigen is not present during lymphocyte receptor formation in the bone marrow.

Question 2

What cytokines are involved in lymphocyte development?

Answer 2

IL-3: formation of immature progenitor cells

IL-7: necessary for commitment of lymphoid lineages

Question 3

define allelic exclusions

Answer 3

gene rearrangement of heavy chain formation can only occur on either maternal or paternal chromosome (cannot switch)

gene rearrangement of light chain (even during receptor editing) can only occur on either maternal or paternal chromosome (cannot switch)

Question 4

Rag1 and Rag2 enzymes

Answer 4

dictate gene rearrangement of heavy and light chains of BCR formation through hairpin loops by joining RSS sequences. also involved in gene beta and alpha chain formation of TCR.

Question 5

junctional diversity

Answer 5

addition of nucleotides randomly at junction between D and J segments catalyzed by terminal deoxyribonucleotidyl transferase (Tdt). leads to further diversity in the third hypervariable region

Question 6

receptor editing

Answer 6

occurs when there is a nonproductive light chain. light chains is rearranged again to rescue B cell

Question 7

What disease would a defect of Rag1 or Rag2 cause in an individual?

Answer 7

severe combined immunodeficiency (SCID)

• individuals lack B, T and NK cells and thus are susceptible to all infections, particularly opportunistic pathogens
• call also be caused by mutations of IL7 cytokine receptor (x-linked version)

Question 8

X-linked agammaglobulinemia

Answer 8

Defect of Btk which delivers signal from pre-BCR for survival. This leads absence of B cells and recurrent infections of extracellular pathogens.