Faculty Bibliography

These studies were performed to establish whether functional receptors for calcitonin gene-related peptide (CGRP) are present on human dendritic cells (DCs) and to investigate potential immunomodulatory effects of CGRP on DCs other than Langerhans cells. Reverse transcriptase-PCR revealed expression of mRNA for a type 1 CGRP receptor by mature and immature blood-derived DCs. Sequence analysis confirmed the identity of the type 1 CGRP receptor (CGRP-R1). Addition of CGRP (10-7 M) to mature and immature DCs resulted in mobilization of intracellular calcium. Treatment of immature DCs with CGRP (10-7 M), before and after maturation in monocyte-conditioned medium, resulted in decreased cell surface expression of HLA-DR MHC class II and the costimulatory molecule, CD86. Treatment of immature DCs with CGRP (10-7 M) also resulted in decreased expression of CD86, but expression of HLA-DR was unchanged. When CGRP-treated mature DCs were used to stimulate allogeneic T cells, proliferative responses were dampened (approximately 50%), especially at low DC:T cell ratios (1:360). This effect was not observed with CGRP-treated, immature DCs. In contrast, CGRP-treated mature or immature DCs were no less efficient than untreated DCs in driving syngeneic T cell-proliferative responses to staphylococcal enterotoxin B. We conclude that mature and immature DCs express type 1 CGRP receptors and that signaling through these receptors may dampen mature DC-driven T cell proliferation most likely via down-regulation of CD86 and HLA-DR

The ability of substance P (SP) to regulate peak benzyl-penicilloyl (BPO)-specific IgE antibody-forming cell (AFC) responses in vivo and the ability of SP and other neuropeptides to regulate BPO-specific memory IgE AFC responses induced in vitro was determined. SP injected subcutaneously into BPO-keyhole limpet hemocyanin (BPO-KLH)-sensitized mice at the time of peak IgE responses suppressed these responses within 48 h (> 90%). The suppression obtained was IgE isotype-specific, dose-dependent, and transient. When spleen cells from immunized mice were cultured for 5 days with BPO-KLH, peak memory IgE AFC responses were induced in vitro. Inclusion of either SP or vasoactive intestinal peptide (VIP), but not neurotensin, serotonin, somatostatin, or gastrin, in cultures suppressed these responses in isotype-specific, dose-dependent fashion (approximately 70%). SP-, but not VIP-mediated suppression of IgE responses was abrogated by inclusion of anti-IFN gamma culture

Previous studies in our laboratory have shown that substance P (SP), injected into benzylpenicilloyl-keyhole limpet hemocyanin (BPO-KLH) sensitized mice at the peak of the benzylpenicilloyl (BPO)-specific IgE response, suppressed these responses in isotype-specific fashion within 48 h. These studies also showed that SP, but not neurotensin (NT), serotonin (5-HT), somatostatin (SOM) or gastrin, suppressed BPO-specific memory IgE antibody-forming cell (AFC) responses induced in vitro, also in isotype-specific fashion. To investigate the mechanisms by which SP suppressed BPO-specific IgE AFC responses were induced in vitro, these responses were induced by culturing spleen cells from BPO-KLH sensitized mice for 5 days with BPO-KLH with or without whole SP, amino terminal SP (SP 1-4: Arg-Lys-Pro-Lys), or carboxy terminal SP (SP 8-11: Phe-Gly-Leu-Met). In some experiments, the SP receptor antagonist (D-Pro2, D-Phe7, D-Trp9)-SP (D-SP) was included in culture. In other experiments anti-interferon monoclonal antibody (anti-IFN gamma mAb) was in culture. Whole SP and SP 8-11, but not SP 1-4, suppressed BPO-specific IgE AFC responses induced in vitro. The suppression obtained was IgE isotype-specific and dose-dependent. Inclusion of SP receptor antagonist (D-Pro2, D-Phe7, D-Trp9)-SP inhibited suppression of BPO-specific memory IgE AFC responses by SP or SP 8-11. The SP-mediated suppression of BPO-specific memory IgE responses appeared to involve interferon gamma (IFN gamma)

The roles of Thy-1+ and AsGM1+ spleen cells and cytokines (IL-4, IL-5, IL-6, IFN-alpha, and IFN-gamma) in regulation of hapten-specific memory IgE antibody-forming cell (AFC) responses induced in vitro were examined. BALB/c mice, injected i.p. with benzylpenicilloyl-keyhole limpet hemocyanin (BPO-KLH) (10 micrograms) on days 0 and 21, were killed on day 60 or day 120. Numbers of BPO-specific IgGI, IgE, and IgA AFC in spleen were determined by enzyme-linked immunosorbent spot assay after 0 to 6 days of culture +/- BPO-KLH. BPO-specific AFC of all isotypes were detected in spleen on day 60, but not on day 120. Day 60 AFC responses did not persist in culture in that no AFC were detected by day 2 of culture +/- BPO-KLH. When either day 60 or day 120 cells were cultured for 3 days with BPO-KLH, BPO-specific AFC responses were induced, and peaked on day 5, with similar numbers of AFC of each isotype induced with day 60 and day 120 cells. On day 60, spleen contained two subsets of Thy-1+ cells: AsGM1- (approximately 32% of total cells) and AsGM1+ (approximately 4%). Depletion and reconstitution experiments established that both subsets were required for induction of BPO-specific IgE AFC responses. Cytokines could not substitute for the Thy-1(+)-depleted cells. However, when unfractionated day 60 cells were cultured with cytokines or anti-cytokine antibodies, BPO-specific IgE AFC responses induced were both IFN-alpha and IL-4 dependent; either increased or decreased by IFN-gamma, depending on its concentration, and unaffected by IL-5 or IL-6