Impairment of cell-mediated immune responses in HTLV-I-associated myelopathy

In order to assess in vivo cell-mediated immune functions in HTLV-I-associated myelopathy (HAM), we immunized 18 HAM patients with dinitrochlorobenzene (DNCB). Of 18 patients, the skin reaction to DNCB was negative in 15. All those 15 patients also showed anergy to PPD-tuberculin and 9 of 15 patients had a persistent lymphocytopenia (less than 1500/mm3). In vitro lymphoproliferative responses to mitogens, assayed by a flow fluorocytometric method, were also significantly depressed in HAM patients when compared to normal controls. The results thus indicate that cell-mediated immune functions are significantly impaired in HAM patients.