Modulation of leucocyte locomotion by interleukin‐1
The influence of interleukin‐1 (IL‐1) upon leucocyte locomotion in vitro was studied, using either casein or zymosan‐activated serum (ZAS) as chemotaxigens. A pre‐incubation of polymorpho‐nuclear cells (PMNC) with ultrapure (purity 99%) human IL‐1 (1 U/ml) for 2 and 5 h followed by a washing step resulted in a significant decrease in leucocyte locomotion against casein (P < 0.0005 and P<0.01, respectively), but not against ZAS (P>0.1). Moreover, the direct addition of this IL‐1 preparation to leucocyte locomotion assays without pre‐incubation produced a similar and significant inhibition of leucocyte locomotion directed against casein (P < 005). This inhibitory effect could not be augmented further by higher concentrations of ultrapure IL‐1. In order to exclude the effect of possibly contaminating cytokines in the ultrapure IL‐1 preparation used, additional assays with recombinant human IL‐1 (rIL‐1) alpha and rIL‐1 beta (1 U/ml) were performed to investigate their influence upon leucocyte locomotion. It was found that both rIL‐1α and rIL‐1β inhibited leucocyte locomotion directed against casein significantly (P < 0.005). Similar to the previous experiments, leucocyte locomotion could not be further inhibited by higher concentrations (10 U/ml) of rIL‐1. Thus, both ultrapure and rIL‐1 were found to have the ability to inhibit leucocyte locomotion in vitro.