Activation of human basophils through the IL-8 receptor.
IL-8 and its structural analogs derived from blood platelets have been proposed as stimuli of IgE-independent basophil activation. In order to clarify the mechanism of action of these peptides, we examined the effects of pure IL-8, connective tissue-activating peptide III (CTAP-III), neutrophil-activating peptide 2 (NAP-2), and platelet factor 4 (PF-4) on blood basophils with and without pretreatment by IL-3, which modulates mediator release. After pretreatment with IL-3, significant histamine release was observed with 10(-8) M and 10(-7) M IL-8 and 10(-7) M NAP-2, but not with the other peptides. At higher concentrations (10(-6) M), however, all IL-8 analogs, as well as the unrelated cationic peptides poly-D-lysine, histone VS, and lysozyme, induced histamine release to variable degrees. Binding and competition studies with [125I]IL-8 revealed specific IL-8R on basophils from a patient with chronic myelogenous leukemia and normal individuals. From 3500 to 9600 receptors with a mean Kd value of 0.15 nM were found on average per chronic myelogenous leukemia and normal basophil, respectively. NAP-2 weakly competed for IL-8 binding. IL-8 and, to a lesser extent, NAP-2 led to a transient rise of cytosolic free calcium concentration ([Ca2+]i), which was independent of a preexposure to IL-3. IL-8 prevented the [Ca2+]i rise induced by NAP-2, but did not influence [Ca2+]i responses to other agonists, e.g. C5a, C3a, or platelet-activating factor. IL-8 induced [Ca2+]i changes and histamine release in IL-3-primed basophils were pertussis toxin sensitive. CTAP-III or PF-4 did not compete for IL-8 binding, did not induce [Ca2+]i changes, and did not influence the [Ca2+]i response to IL-8 and NAP-2. This study shows that IL-8 and NAP-2 activate human basophils by a receptor-mediated mechanism similar to that operating in neutrophils. At high concentrations histamine release can also be induced by cationic peptides by a mechanism that does not involve the IL-8R, and probably depends on cationic interactions.
Krieger
M
M
Institute of Clinical Immunology, University of Bern, Switzerland.
Brunner
T
T
Bischoff
S C
SC
von Tscharner
V
V
Walz
A
A
Moser
B
B
Baggiolini
M
M
Dahinden
C A
CA
D000595:Amino Acid Sequence; D001491:Basophils / Q000187:drug effects* / Q000502:physiology; D001667:Binding, Competitive; D001779:Blood Coagulation Factors / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D006636:Histamine Release / Q000187:drug effects; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology; D016209:Interleukin-8 / Q000378:metabolism / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010455:Peptides / Q000494:pharmacology; D037342:Pertussis Toxin; D010978:Platelet Factor 4 / Q000494:pharmacology; D011971:Receptors, Immunologic / Q000187:drug effects*; D023062:Receptors, Interleukin-8A; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D001620:beta-Thromboglobulin
D001779:Blood Coagulation Factors; D007377:Interleukin-3; D016209:Interleukin-8; C061615:PPBP protein, human; D010455:Peptides; D011971:Receptors, Immunologic; D023062:Receptors, Interleukin-8A; D010566:Virulence Factors, Bordetella; D001620:beta-Thromboglobulin; D010978:Platelet Factor 4; C009862:connective tissue-activating peptide; C018329:low affinity platelet factor 4; D037342:Pertussis Toxin; D002118:Calcium