Changes in tristetraprolin (TTP) expression by leukocytes after lipopolysaccharide (LPS) stimulation in vitro. (a) LPS induced TTP expression in all leukocytes. Results are expressed as the LPS-induced increase in TTP specific staining over baseline expression. Significant increases are shown with respect to time 0 (*P < 0.05 monocytes or lymphocytes; #P < 0.05 neutrophils; n = 8). Monocyte recovery was poor at time points beyond 4 hours and these results are excluded. (b) Confocal microscopy shows the upregulation of TTP in neutrophils 2 hours after LPS stimulation. Neutrophils before (i-iii) and after (iv-vi) LPS stimulation. (i,iv) transmitted light (differential interference contrast) image of the cell; (ii,v) TTP (FITC); (iii,vi) composite image, nuclear material stained red with propidium iodide.