Are CD8+ (cytotoxic) T cells and  CD4+ Helper T cells generated in the thyroid and express the T-cell receptor?
Through positive selection, double-positive cells in the thymus differentiate into CD4(+) or CD8(+) T single-positive cells that subsequently develop into different types of effective T cells, such as T-helper and cytotoxic T lymphocyte cells, These two cell types are derived from common precursors in the thymus.