Morphological evidence for the location of calcitonin gene-related peptide (CGRP) immunoreactivity in rat lymphocytes

Calcitonin gene-related peptide (CGRP) is widely distributed in sensory neurons and nerve fibers. It was shown recently in our laboratory that there was CGRP-immunoreactivity (CGRP-ir) in extract of rat lymphocyte of thymus and mesenteric lymph node by radioimmunoassay and reversed-phase HPLC. The aim of this study was to detect the CGRP-ir location in the rat lymphocyte by immunocytochemical method. Single cells isolated from thymus and mesenteric lymph node of male Wistar rat (200-250 g) were suspended in RPMI-1640 medium. After adhesion to plate wall and through nylon wool fiber columns, T cell-riched suspension was obtained. Immunocytochemical ABC method was performed in cell suspension, the specific antiserum (1:200 diluted) was rabbit anti-human CGRP. The cells were examined under light microscope after smeared on glass slide by Shandon Cytospin. The results showed that some lymphocytes were CGRP-ir positive. The positive granules were seen as ring, plaque, cap or spot distributing on the surface or inside the cell. The results indicate that CGRP-ir may be located in some rat T lymphocytes. This work provides new information about the interaction between the nervous and the immune systems. The functional significance of CGRP located in lymphocytes needs to be further studied.