CD4 and thymus neoplasm: In an attempt to immortalize immature T cells expressing a known T-cell antigenreceptor (TCR), Thy-1/c-myc transgenic mice were bred to αβ TCR transgenic mice (F5),and CD4+ CD8+ cell lines were established from thymic tumors in double-transgenic mice.These cells expressed high-level heat-stable antigen (HSA) and were able to undergoprogrammed cell death upon induction with steroids and CD3 cross-linking, but not withcognate peptide.