T cells with α:ß or γ:δ receptors arise from a common progenitor
Lymphoid tissue; epidermis;
Intraepithelial (intestine, reproductive
tract)
Innate immunityè recognize target directly (free Ag or
Ag presented by non-MHC)
Expression of CD4 and CD8
HSP, non peptide ligand: phosphorylated
ligand, lipid, unorthodox nucleotides, MHC IB
Evidence for common
lineage?
Rearrangement order
Signaling competition
of TcRγ:δ and TcRß:preTα for lineage directing ligand