ABSTRACT
Mashhad, a city in northern Iran, is a newly recognized endemic area for a retrovirus, the Human T-cell Lymphotropic Virus type I [HTLV-I]. This virus is the causative agent of a chronic slowly progressive cord syndrome called HTLV-I associated with Human T-cell virus type I-associated myelopathy or/tropical spastic paraparesis [HAM/TSP] and has tropism for CD4+ T- cells, which results in T-cell activation that escape the autocrine pathway. The purpose of this study was to determine the immuno-phenotypic features of peripheral blood lymphocytes of HAM/TSP patients, especially differential expression of interleukin-2 receptor