Expression of calcitonin gene-related peptide (CGRP) mRNA in rat lymphocytes

We recently found that calcitonin gene-related peptide (CGRP)-like immunoreactivity was present in lymphocytes of rat thymus and lymph node. In order to investigate whether these cells were capable of synthesizing CGRP, CGRP mRNA of rat dorsal root ganglia, thymocytes and mesenteric lymph node lymphocytes were determined by reverse transcription and polymerase chain reaction (RT-PCR) utilizing synthetic oligonucleotides bracketing a portion of the calcitonin/CGRP gene. A discrete band of the expected size of 90 base pairs was found in the dorsal root ganglia (positive control), and in both thymocytes and mesenteric lymph node lymphocytes. These data strongly suggest that CGRP is not only an important neuropeptide, but it is also synthesized in lymphocytes of both thymus and lymph nodes, which is identical to that in sensory neurons. CGRP from lymphocytes may act as an immunomodulator and serve as a common ligand in immune and nervous systems.