Sllmmsr~The cellular infiltrates of certain inflammatory processes found in parasitic infection or in allergic diseases consist predominantly of eosinophilic granulocytes, often in association with activated T cells. This suggests the existence of chemotactic agonists specific for eosinophils and lymphocyte subsets devoid of neutrophil-activating properties. We therefore examined four members of the intercrine/chemokine superfamily of cytokines (monocyte chemotactic peptide 1 [MCP-1], RANTES, macrophage inflammatory protein 1ix [MIP-ltx], and MIP-1/3), which do not activate neutrophils, for their ability to affect different eosinophil effector functions. R.ANTES strongly attracted normal human eosinophils by a chemotactic rather than a chemokinetic mechanism with a similar efficacy as the most potent chemotactic myeloid cell agonist, C5a. MIP-ltx also induced eosinophil migration, however, with lower efficacy. RANTES and MIP-lo~ induced eosinophil cationic protein release in cytochalasin B-treated eosinophils, but did not promote leukotriene C4 formation by eosinophils, even after preincubation with interleukin 3 (IL-3), in contrast to other chemotactic agonists such as C5a and formyl-methionyl-lencyl-phenylalanine (FMLP). RANTES, but not MIP-ltx, induced a biphasic chemiluminescence response, however, of lower magnitude than C5a. RANTES and MIP-lo~ both promoted identical transient changes in intracellular free calcium concentration ([Ca2+]i), with kinetics similar to those induced by chemotactic peptides known to interact with G protein-coupled receptors. No cross-desensitization towards other peptide agonists (e.g., C5a, IL-8, FMLP) was observed, suggesting the presence of specific receptors. Despite its weaker eosinophil-activating properties, MIP-lol was at least 10 times more potent on a molar basis than R.ANTES at inducing [Ca 2+ ]i changes. Interestingly, RANTES deactivated the MIP-lcz-induced [Ca2+]i changes, while the R.ANTES response was preserved after MIP-lcz stimulation. MCP-1, a potent monocyte chemoattractant and basophil agonist, as well as MIP-1/3, a peptide with pronounced homology to MIP-lo~, did not activate the eosinophil functions tested. Our results indicate that R.ANTES and MIP-ltx are crucial mediators of inflammatory processes in which eosinophils predominate.

Chemotactic cytokines related to interleukin-8 (IL-8; CXC-chemokines) or monocyte chemotactic protein-1 (MCP-1; CC-chemokines) have been shown to stimulate human basophils, and are considered important tissue-derived mediators of inflammation. We have studied the effects of four CC-chemokines and show that MCP-1, RANTES (regulated on activation, normal T expressed and secreted) and macrophage inflammatory protein-1 alpha (MIP-1 alpha) are potent basophil agonists inducing a rapid change of cytosolic free calcium ([Ca2+]i), the release of histamine and sulfido-leukotrienes, and chemotaxis. MCP-1 was the most potent stimulus of release, and the only chemokine that induced marked exocytosis in basophils without pretreatment with interleukin-3. RANTES was the strongest stimulus of chemotaxis, but only a moderate stimulus of release. MIP-1 alpha elicited relatively weak chemotaxis and release responses, but was effective at considerably lower concentrations than MCP-1 and RANTES. MIP-1 beta, by contrast, despite its high homology to MIP-1 alpha, was totally inactive. Normodense human eosinophils, tested for comparison, responded in a similar fashion to RANTES and MIP-1 alpha, but were unresponsive to MCP-1 and MIP-1 beta. All CC-chemokines except MIP-1 beta induced a similar rapid and transient rise of [Ca2+]i that was sensitive to pertussis toxin, indicating that they activate basophils via G-protein-coupled receptors. Cross-desensensitization experiments indicate that basophils bear different CC-chemokine receptors. Some interact selectively with MCP-1 or RANTES, while others are shared by RANTES and MIP-1 alpha.

Sumnlfl~Cytokines belonging to the RANTES/SIS family are highly induced in a number of pathophysiological processes such as autoimmune disorders, cancers, atherosderosis, and chronic inflammation. However, apart from their chemotactic activity on monocytes and particular lymphocyte types, the biological activities in the human system of this recently discovered cytokine family are largely unknown. Here we report that one family member, described as monocyte chemotactic protein 1 (MCP-1), strongly activates mature human basophils in a pertussis toxin-sensitive manner. MCP-1 causes a rise in the cytosolic free calcium level in basophils and monocytes, but not in other blood leukocyte types, and triggers basophil degranulation at low concentrations (ED50 = 3-10 riM). Thus, MCP-1 is a cytokine capable of directly inducing histamine release by basophils. Furthermore, MCP-1 promotes the formation of leukotriene C4 by basophils pretreated with interleukin 3 (IL-3), Ib 5, or granulocyte/macrophage colony-stimulating factor. MCP-l-induced basophil mediator release may play an important role in allergic inflammation and other pathologies expressing MCP-1.

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A polyclonal antibody directed against S.cerevisiae proteins which bind to a m7GDP-agarose affinity column (1) was used to screen a S.cerevisiae cDNA library in the vector kgtll (2). A

Biologically active molecules affecting basophil function can be divided into 4 groups according to their capacity to induce basophil degranulation and/or leukotriene generation: (1) full agonists such as anti-IgE or fMLP, which induce both histamine and leukotriene release; (2) partial agonists such as C5a, which induces degranulation only; (3) incomplete agonists such as neutrophil-activating peptide-1, platelet-activating factor or C3a, which induce mediator release only after cytokine preincubation, and (4) basophil response modifiers, such as interleukin-3, interleukin-5 and granulocyte/macrophage-colony-stimulating factor, which (a) enhance the releasability to all basophil agonists, (b) change the mediator profile, (c) enhance the rate of mediator release, (d) render basophils responsive to lower agonist concentrations and (e) render basophils responsive to incomplete agonists. We demonstrated that histamine release and de novo synthesis of lipid mediators are clearly separately regulated, and that combined actions of different molecules are of importance. In particular, the type(s), the time interval and the sequence of action of basophil-activating molecules are crucial for the final outcome of the basophil release reaction.

The intracellular signaling pathways regulating the synthesis of leukotrienes by myeloid cells are largely unknown. In addition, the signal transduction mechanisms utilized by the cytokine receptor family are still poorly understood. The fact that in mature human basophils the synthesis of leukotriene C4 (LTC4) induced by C5a is strictly dependent on a short preincubation with the cytokine interleukin-3 (IL-3), allowed us to investigate the metabolic requirements for LTC4 synthesis, and also to provide some information on early signal transduction mechanisms of IL-3 in these differentiated, non-dividing blood leukocytes. IL-3 itself does not alter intracellular free calcium concentration ([Ca2+]i) in basophils, whereas C5a induces a transient rise independent of IL-3 pretreatment, indicating that the priming effect of IL-3 cannot be explained by alterations in [Ca2+]i changes. The protein kinase C inhibitor staurosporine did not inhibit C5a-induced histamine release nor IL-3-dependent LTC4 formation in contrast to the IgE receptor-dependent basophil response. Activation of protein kinase C (PKC) by phorbol-12-myristate-13-acetate (PMA) induced histamine release without leukotriene formation. PMA-treated basophils did not produce LTC4 in response to C5a. Rather, PMA blocked the IL-3 effect on C5a-induced LTC4 synthesis. Only the C5a signal but not the IL-3 effect was pertussis toxin sensitive. Two unrelated tyrosine kinase inhibitors, tyrphostin RG-50864 and herbimycin A, were both very efficient blockers of IL-3-dependent lipid mediator formation whereas C5a-induced histamine release was preserved. Thus LTC4 formation does not require activation of a staurosporine-sensitive serine/threonine kinase. To the contrary, IL-3-dependent LTC4 formation appears to be regulated by serine/threonine and tyrosine phosphorylation in an antagonistic manner.

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