•Production of new
lymphocytes (lymphopoiesis): in central lymphoid tissues
• B cells: bone marrow; fetus (fetal
liver, yolk sac)
• T cells: precursor
cells in bone marrow and then migrate to thymus
•
•Ag specificity of
an individual lymphocyte is determined early in its differentiation by
gene rearrangement. The early stages of B and T cell development
proceed along broadly similar lines.
•
•Specificity and
affinity of the receptors determine the fate of the immature
lymphocytes
•
• -Positive
selection: interact weakly with self Ag. Receive signals to survive. Eg. α:β T cells recognize peptide bound to MHC
• -Negative
selection: lymphocytes whose receptors bind strongly or not at all to self
antigen and receive signals to die (immunological tolerance).
•