Factors influencing the expression of interleukin-1 beta in cultured rainbow trout (Oncorhynchus mykiss) leucocytes.

The dose dependency and kinetics of lipopolysaccharide (LPS) induced interleukin-1beta (IL-1beta) mRNA expression in rainbow trout leucocytes has been studied. Northern blot analysis revealed weak hybridisation of a trout IL-1beta probe to RNA from head kidney leucocytes stimulated with 0.1 microg LPS/ml, with a large increase in IL-1beta transcript level seen between 0.1 and 1.5 microg LPS/ml. Using 5 microg LPS/ml expression was first detectable 1-2 h post-stimulation. By 4 h post-stimulation maximal induction was seen but by 24-48 h the level had fallen and by 72 h no transcript was detectable. Culture temperature had a marked effect on IL-1beta expression, with low temperatures inhibiting transcription. Indeed, an eight-fold increase in IL-1beta transcript level was seen between cells cultured at 4 degrees C and 22 degrees C. Preincubation with cortisol was also shown to inhibit LPS-induced IL-1beta expression.