Apparent functionality but impractical quantification of neurotensin receptors on human peripheral lymphocytes

Neurotensin (NT), a neuromodulator, is also thought to play an immunomodulatory role. We sought to confirm the effects of NT on proliferation in human peripheral blood lymphocytes (PBLs; n = 10), to characterize the binding properties of the NT receptor using Scatchard analysis, and to measure NT receptors using blood volumes (50 ml) applicable to clinical investigation. Incubation of phytohemagglutinin-stimulated PBLs with NT (10[-10] to 10[-13] M) in the presence of 0.07% normal human serum (72 h at 37 degrees C) significantly enhanced proliferation (p < 0.001), which is consistent with PBLs possessing functional NT receptors. However, the various experimental conditions tested constantly yielded low specific NT binding to human PBLs, and hence Scatchard analysis was impossible for 50-ml blood samples. Our data confirm the existence of a link between NT and the immune system and support a physiological significance for this link. However, measurement of NT receptor binding in readily available cells proved unsuitable for clinical investigation.