Culture Conditions Dictate Whether Mouse Fetal Thymus Lobes Generate Predominantly γ/δ or α/βT Cells

Summary

Thymus lobes from 14 day-old mouse embryos cultured submerged in r-IL-2 generated a mixture of CD8α⁺ /CD4⁻ and CD8⁻;/ γδTcR expressing cells (Ceredig et. al. 1989). Based upon Northern analysis with TcR constant region probes, no αβ T cells could be identified in these cultures. Submerged lobes also showed responsiveness to IL-7. In contrast, when cultured at an air liquid interface as organ cultures (OC), most cells appeared to express αβTcR (Ceredig 1988). Thus depending on the mode of culture, fetal thymus lobes generate predominantly γδ or αβ T cells; it is unclear how this difference is regulated. Previous phenotypic and functional experiments suggested that γδ T cells may be present in OC. In order to study γδ T cells in both submerged lobe and OC, we have carried out three colour flow microfluorimetric analysis ofγδTcR, abTcR, CD3, Jlld and CD8β expression by subpopulations of CD8α and CD4 defined thymocytes. In addition, using V γ-specific oligonucleotides and the polymerase chain reaction, we have begun identifying and sequencing the Vγ repertoire of γδT cells in these mouse fetal thymus cultures.