Immunocomplexes stimulate different signalling events to chemoattractants in the neutrophil and regulate L-selectin and β2-integrin expression differently

Y. Molad, K. A. Haines, D. C. Anderson, J. P. Buyon, B. N. Cronstein

Research output: Contribution to journalArticlepeer-review

Abstract

Neutrophils express receptors for numerous phlogistons which, when occupied, trigger distinct signal-transduction pathways. Previous studies have shown that stimulation of neutrophils with chemoattractants induces shedding of the adhesive molecule L-selectin and increased expression of the β-integrin CD11b/ CD18. We determined the effect of ligation of classic, G-protein-linked chemoattractant receptors [C5a, interleukin-8 (IL-8), formylmethionyl-leucylphenylalanine (FMLP) and substance P], receptors for the Fc portion of IgG (Fcγ receptors) and receptors for transforming growth factor β (TGFβ) on expression of adhesive molecules by neutrophils and the stimulus-transduction mechanisms thought to mediate these changes. We were surprised to observe that occupancy of Fcγ receptors by immunocomplexes (BSA-anti-BSA) stimulated increased expression by neutrophils of CD11b/CD18 at concentrations which did not affect L-selectin expression (EC50 9 μg/ml versus 350 μg/ml respectively, P < 0.00001, n = 5). In contrast, similar to previous studies, recombinant C5a, recombinant IL-8 and FMLP all stimulated increased expression of CD11b/CD18 (170-260% of basal, P < 0.001, n = 5) and shedding of L-selectin (56-75% reduction from basal, P < 0.001, n = 5) at similar concentrations and with similar potencies (EC50 = 2, 5, and 3 nM respectively). In contrast, neither TGFβ1 nor, surprisingly, substance P affected expression of CD11b/CD18 or L-selectin. The regulation of expression of CD11b/CD18 or L-selectin in response to FMLP or immunocomplexes was unaffected by cytochalasin B (5 μg/ml) or the tyrosine kinase inhibitor tyrphostin-25 (25 μM). Although occupancy of both chemoattractant (FMLP) and Fcγ receptors stimulated increments in the second messenger diacylglycerol, disruption of actin microfilaments by cytochalasin B enhanced diacylglycerol generation in response to FMLP but not in response to ligation of Fcγ receptors. Moreover, both FMLP and immune aggregates provoked fluxes of intracellular Ca2+ concentration which differed with respect to both magnitude and kinetics and did not correlate well with regulation of adhesive-molecule expression. As upregulation of CD11b/CD18 is tightly linked to exocytosis of specific granules, these results suggest that shedding of L-selectin by activated neutrophils is not linked to exocytosis. These studies provide further evidence that receptors for chemoattractants and immunocomplexes on the neutrophil are linked to multiple signalling pathways.

Original languageEnglish
Pages (from-to)881-887
Number of pages7
JournalBiochemical Journal
Volume299
Issue number3
DOIs
StatePublished - 1994
Externally publishedYes

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