Abstract
Reports suggest that vasoactive intestinal peptide (VIP) binds to lymphocytes and modulates immune responses. The intestines are richly innervated with VIP-producing nerves. Thus, VIP from nerves or other sources may participate in mucosal immunoregulation. To explore this hypothesis further, murine intestinal mucosa inflammatory cells were scrutinized for functional VIP receptors. An [ 125I]VIP competitive binding assay characterized VIP receptors. Unfractionated lamina propria inflammatory cells bound [ 125I]VIP specifically. This binding was abrogated by T cell depletion. The VIP receptor on lamina propria T cells was of a single class with a K d of 9.08 × 10 −9 M. It bound PHI and other peptide analogs poorly. The intestinal epithelial cell had a high-affinity VIP receptor ( K d 4.17 × 10 −10 M) that bound one VIP analog with moderate affinity. Both VIP and ConA stimulated mucosal inflammatory cells to release interleukin-5 (IL-5). Mucosal inflammatory cells depleted of T cells did not release IL-5 in response to VIP or ConA. It is concluded that: (1) some murine mucosal T lymphocytes have VIP receptors that may be distinct from those displayed on mucosal epithelial cells; (2) VIP affects mucosal T lymphocyte function.
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