T cell vasoactive intestinal peptide receptor subtype expression differs between granulomas and spleen of schistosome-infected mice

Abstract

Granulomas form in the liver and intestines of mice infected with the parasite Schistosoma mansoni. Vasoactive intestinal peptide (VIP) is a neurokine that can modulate aspects of the immune response by acting through receptors within the granuloma. Cloned are two novel VIP receptor (VIPR) mRNAs (VIPR1 and VIPR2) that also bind a second neurokine called pituitary adenylated cyclase-activating polypeptide (PACAP). The objective of this study was to determine if granulomas express either VIPR1 or VIPR2. Using a radioligand-binding assay, it was established that PACAP is as effective as VIP at displacing radiolabeled VIP from splenocytes and granuloma cells, and that most if not all VIPRs in the spleen and granulomas bind PACAP. PCR amplification of reverse transcribed RNA determined that granulomas express both VIPR1 and VIPR2 mRNAs. Gel electrophoresis and nucleotide sequencing confirmed the authenticity of the PCR products. Also, both receptor subtypes were amplified from several granuloma CD4+ T cell lines; yet reverse transcribed RNA from T cell-depleted, dispersed granuloma cells had only VIPR1 RNA. It is notable that reverse transcriptase-PCR detected only VIPR1 in the thymus and spleen, which are organs rich in T lymphocytes. Thus, the granulomas and spleens from mice with schistosomiasis contain cells that display authentic VIP/PACAP receptors. Moreover, these data suggest that T cells in different compartments vary in VIPR subtype expression. VIPR1 and VIPR2 may have different physiologic roles in inflammation.