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Recently, we isolated some new and functionally identical panchemotactic factors (Lipid-like leucocyte activators = LILAs) from Candida albicans, Saccharomyces cerevisiae and various dermatophytes, which are chemotactic for human neutrophilic and eosinophilic granulocytes as well as for monocytes. In order to answer the question, whether human neutrophilic granulocytes express a specific receptor for LILA, we now investigated the mobilisation of the intracellular second messenger calcium within human neutrophils which were stimulated with LILA. Furthermore, LILA-mediated activation of neutrophils was subjected to desensitisation experiments with the well known neutrophil activators 5-oxo-eicosatetraenoic acid, leukotriene B4, platelet activating factor, C5a, Interleukin-8, and N-for-myl-methionyl-leucyl-phenylalanin (FMLP). The intracellular calcium concentration was measured by use of the fluorescence indicator FURA-2/AM. As a result we were able to show a significant dose-dependent increase in the intracellular calcium concentration after stimulation of human neutrophils with LILA. The desensitisation experiments revealed no cross-desensitisation between LILA and the well known stimuli. Our results show that LILA induces an intracellular calcium signal in addition to its panchemotactic activities. Therefore, calcium may act as second messenger in LILA-stimulated activation of neutrophils. Since LILA-mediated activation was maintained in the desensitisation experiments, LILA-specific receptors may be present on human neutrophils.

The possibility of changing N-terminally protected tripeptides with chemotactic activity into antagonists by variation of the protecting group was investigated. Chemotactic activity in the agarose test was shown for a series of new structurally related formylated tripeptides. The effect could be antagonised with one exception by Boc-analogues. These antagonists are very likely bound to the same membrane receptor of polymorphonuclear leucocytes as the chemotaxins. The antagonists do not influence the activity of the naturally occurring chemotaxin C5a. The syntheses of the test compounds are described.

NAF/NAP-1 is a novel tissue-derived chemotactic peptide. It consists of 72 amino acids and has no sequence homology to known cytokines. NAF/NAP-1 is produced by a wide variety of cells after stimulation with interleukin-1, tumor necrosis factor or endotoxin, and has the properties of a local mediator of neutrophil recruitment into diseased tissues. There are indications that NAF/NAP-1 is important in the pathophysiology of inflammatory conditions such as psoriasis, idiopathic pulmonary fibrosis, asbestosis, adult respiratory distress syndrome and different forms of arthritis.

Boc-protected peptides antagonise leucocyte chemotaxis induced by formylated derivatives. Other protecting groups similar to Boc were investigated to see if they also produce chemotaxin antagonists when combined with the chemotactic standard sequence' Met-Leu-Phe. Four related acylated tripeptides were synthesized and studied in the agarose test. It could be proved that they influence the chemotaxin HCO-Met-Leu-Phe-OH as potent antagonists.