DISSOCIATED EXPRESSION OF GRANULOCYTE-MACROPHAGE CSF AND IL-3 IN SHORT-TERM T-CELL CLONES FROM NORMAL MICE

Granulocyte-macrophage colony-stimulating factor (CM-CSF) and IL-3 are generally thought to be produced in a coordinated fashion by all acti vated T cells. We have examined this premise using quantitative kineti c analyses of the expression of CM-CSF and IL-3 in clonal cultures of mouse T cells for the first two weeks following in vitro stimulation w ith solid-phase TCR- and accessory molecule-specific mAbs. We demonstr ate that 1) differential secretion of CM-CSF and IL-3 is a feature of high proportions of CD8+ and CD4+ T cell clones, for extended periods of time following activation; 2) multiple patterns of expression of th ese two cytokines can occur, including equivalent, GM-CSF-biased, and IL-3-biased production, and a pattern that switches over a period of d ays from GM-CSF-biased to IL-3-biased production; 3) the disparate rel ative levels of secretion are not due to differential consumption of e ither cytokine; 4) altered T cell activation by addition of CD28 costi mulation accelerates both GM-CSF and IL-3 production but biased patter ns of expression are retained, and 5) most T cells are not pre-committ ed to a particular pattern of relative GM-CSF and IL-3 expression; ins tead, the potential for multiple patterns may persist for several days following in vitro activation. The results indicate that T cells have the potential to display previously unrecognized diversity of express ion of GM-CSF and IL-3.