In vivo and in vitro repertoire of CD3+CD4 CD8 thymocytes |
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Authors: | Papiernik Martine; Pontoux Christiane |
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Institution: | INSERM U 25, CNRS UA 122, Hôpital Necker 161 Rue de Sèvres, 75015 Paris, France |
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Abstract: | CD4-CD8- thymocytes contain a cell subset which expresses thecomplete CD3-TCR complex ( / or / ) of which the ontogeny andfiliation are unknown. One of the questions is whether thispopulation can be intrathymically selected, an obligatory stepfor the mature CD4+ and CD8+ cell differentiation pathway, orif the absence of CD4 and CD8 allows them to escape thymic selection.The repertoire of CD3 + CD4 - CD8 - (CD3 + DN) thymocytes wasanalyzed in different strains of mice with different combinationsof H-2 and Mls expression. The expression of Vß8.1in freshly isolated CD3+ DN cells is the highest in Mls-lb miceand the lowest in MIS-la and F1 mice, suggesting that selectionagainst this specificity can be achieved in vivo. By contrast,a low percentage of Vß6+ cells is found in all thestrains, with no correlation according to MIS expression. Invitro culture of DN thymocytes with IL-1 and IL-2 leads to theproliferation of CD3+ DN cells. In vitro culture amplifies thein vivo pattern of Vß8.1 expression, while Vß6+cells only expand in DN cells of 66 and 61002 Mls-lb mice withthe same genetic background. These results show: (i) CD3+ DNthymic cells can be intrathymically selected but the repertoireis different from that of mature T cells; (ii) Vß6and Vß8.1 selection do not follow the same pattern;(iii) this repertoire can be modified by In vitro culture, towarda more mature type; and (iv) comparison of DN cell repertoireof BALBlc, BALB.D2 (congenic for MLs), and other strains ofmice suggests a multigenic control for this selection, and aninvolvement of background genes. |
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Keywords: | thymus CD4-CDB- thymocytes T cell receptor selection lymphokines |
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