To the Editor.
—Peripheral blood mononuclear leukocytes (MNL) from four tropical spastic paraplegia (TSP), ten multiple sclerosis (MS), and 28 Guillain-Barré syndrome (GBS) cases were studied for stimulation with sciatic nerve basic proteins—peripheral (PNS) and central nervous system (CNS) proteins. All TSP cases showed blastogenesis with both PNS and CNS proteins. Cases of MS had mainly CNS protein-sensitive populations, as expected. Although GBS cases did not have any cranial nerve involvement, 50% of MNL samples showed stimulation with CNS protein concomitantly with PNS protein. The finding has been discussed in light of other findings in TSP, viz, human T-cell lymphotropic virus-1 (HTLV-1) association. It has been proposed that HTLV-1 or other viruses implicated in causation of these diseases induce altered antigens on T lymphocytes, resulting in anti-T-cell response. The crossreactivity of T-cell and brain antigens precipitates the neurologic complications. Also, this may be the cause of immune imbalance, which is