Effect of LTB4 and its isomers on human leucocyte migration into skin chambers

The in vivo chemotactic effect of LTB4 and of its isomers, 6-trans-LTB4, 12 epi-6-trans-LTB4 and 5S, 12S-DHETE, was tested with a skin chamber technique in healthy volunteers and in parallel in vitro with an under-agarose technique. LTB4 had an in vivo chemotactic effect at 10(-7) mol/l in 24-hour experiments, while its isomers had no in vivo chemotactic effect at this concentration. LTB4 was also in vitro a more effective attractant than its isomers. In addition, C5ades Arg was tested using zymosan-activated serum, and was found to have an in vivo chemotactic effect at 1.5 X 10(-10) mol/l. However, when LTB4 and C5ades Arg were studied in 6-hour experiments in skin chambers there was an alteration in relative potency, LTB4 being relatively more potent at shorter test durations. This is most likely due to metabolisation of LTB4 in the presence of PMN:s and precludes a strict comparison of the in vivo chemotactic effects of LTB4 and C5ades Arg. When zymosan-activated serum or LTB4 was replaced by PBS after six hours in skin chamber experiments more leukocytes accumulated in the chambers at 24 hours than in chambers containing PBS for the whole 24 hour period. The reason for the increased migration even after the removal of the chemo-attractants as well as the relevance of LTB4 and C5a as chemo-attractants in the inflammatory process is discussed.