In vivo and in vitro repertoire of CD3+CD4-CD8- thymocytes.

CD4-CD8- thymocytes contain a cell subset which expresses the complete CD3-TCR complex (alpha/beta or gamma/delta) of which the ontogeny and filiation are unknown. One of the questions is whether this population can be intrathymically selected, an obligatory step for the mature CD4+ and CD8+ cell differentiation pathway, or if the absence of CD4 an CD8 allows them to escape thymic selection. The repertoire of CD3+CD4-CD8- (CD3+ DN) thymocytes was analyzed in different strains of mice with different combinations of H-2 and Mls expression. The expression of V beta 8.1 in freshly isolated CD3+ DN cells is the highest in Mls-1b mice and the lowest in Mls-1a and F1 mice, suggesting that selection against this specificity can be achieved in vivo. By contrast, a low percentage of V beta 6+ cells is found in all the strains, with no correlation according to Mls expression. In vitro culture of DN thymocytes with IL-1 and IL-2 leads to the proliferation of CD3+ DN cells. In vitro culture amplifies the in vivo pattern of V beta 8.1 expression, while V beta 6+ cells only expand in DN cells of B6 and B10D2 Mls-1b mice with the same genetic background.(ABSTRACT TRUNCATED AT 250 WORDS)