Question

Lymphocyte Development 1. B cell development in the bone marrow shares may features with T cell development in the thymus. A) Discuss the two major goals of lymphocyte development? B) Compare and contrast the ordered steps of receptor rearrangement in B and T cells. C) What cell surface molecules make up the pre-B cell receptor and the pre-T cell receptor and are they only required for development?

Answer 1

B cells are generated and develon in the specialised micro- environment of Bone marrow. while the thymus provides a specialized and architecturally nized micror environment for development of Icell: of lymphocyte A. Two major development goals are :- is to ensure that all T-celle have functional TCR acell - Receptor) ilov lectores Auto reactive cells are deleted a-cell Receptor is a protein complex et found on surface of 1-cello that is responsible! for recognising fragments of antigen as peptides bound to major his to compatibility complex molecules (MHC) tot Receptor selection regulates the Process of VDJ Recombination which can alter or fix antigen receptor specificity. Receptor selection is carried out in

Both I and B cell - T-cell Receptor gene segment rearrange during în cell development to form complete N- domains exons. → T-cell takes Receptor place gene re-arrangement in thymus However gone rearrangement mechanism are similar for B and T cells All known defects in genes that control NCBI recombination affect B and T-cell equally for B cells heavy chain lows is re-arranged first . If re-arrangement is successfu. and a pre-B-cell receptor is made heary chain gene rearrangement ceases and resulting pre- B cells Proliferate. followed by start of 1 re-arrangement at a light locus Pocell Receptor gene segments. rearrange during 9- cell developme- to form complete ur domain exons TD I I I Á further shared feature of

immunoglobulin receptor gene and rocell rearrangement Nucleotides in Tunction between ] the VD and 5 gene segments of re-arranged TC Rp gene Pre - Bocell troch expreases the pre B cell receptor (I gul on its surface maturation in Bone marrow ends with nadine B cell that expresses B cell receptor Lage containing Igm and ID capable of recognising an antigen . These cell then leave Bone marrow B cell recognize intact antigens , T cell recognize fragments of protein antigen that have been partly degraded inside antigen Presenting cell. The peptide fragments are then carried to surface of Presenting cell on special molewles called muc Proteins which present the fragments to To cell