Paraaortic foci cells differentiate into T cells after intrathymic injection in irradiated chicks. E4 H.B19ov⁺cells from the paraaortic foci area of one embryo were injected intrathymically into ov^- recipients. The thymocytes were analyzed 2 weeks later by immunofluorescence flow cytometry: ov, TCRγδ and ov, TCR Vβ1. Each dot plot presents 50,000 events for the gated mature thymocyte population. In dot plots corresponding to recipient injected with paraaortic foci cells, ov⁺, ov⁺ TCRγδ⁺, and ov⁺TCRβ⁺ thymocytes represented 17%, 0,5%, and 7.5% of total thymocytes, respectively.