Treatment of fetal thymic organ culture with IL-1 leads to accelerated differentiation of subsets of CD4-CD8- cells.

Using fetal thymic organ culture (FTOC), we describe the effects of IL-1 on T cell differentiation, particularly within the CD4-CD8- subset. While treatment of FTOC with IL-1 led to a modest reduction in total thymocyte yield, it induced an increase in the percentage of CD4-CD8- cells that express IL-2R early in culture and a decrease in the number of their precursors (CD44+IL-2R- cells). The increase in the percentage of cells expressing IL-2R was not accompanied by an increase in the number of these cells. At later time points these IL-2R+ cells (and their precursors) were reduced relative to controls. The total number of CD4-CD8-CD3- precursor cells in IL-1-treated cultures was reduced to approximately half that in controls at Day 12 of culture. However, only minor inhibition of total cell number was observed, which, taken together with the greater frequency of IL-2R+ precursors, suggests that this depletion of the pool of precursors may have been due to the induction of premature differentiation rather than to its inhibition.