Immunology
The rearrangement of T cell receptor (TCR) genes g and d occur in series of cells expressing variable Vg and Vd gene segments. The lymphoid precursor cells originate in the bone marrow and move to the thymus. Preliminary T cells are devoid of TCR, CD4 and CD8 molecules and are called double negative thymocytes . These double negative T cells may be further categorized into four phases of differentiation (DN1, CD44+CD25-; DN2, CD44+CD25+; DN3, CD44-CD25+; and DN4, CD44-CD25-) . CD44 is a cell adhesion molecule and CD25 serves as the IL-2 receptor. Passage into the DN2 and DN4 stages ...
