CEREBROSPINAL-FLUID ATYPICAL LYMPHOCYTES IN JAPANESE ENCEPHALITIS

Among atypical lymphocytes (AL) examined morphologically and immunohis tochemically in the cerebrospinal fluid (CSF) of adult patients with e ncephalitis, we distinguished a CD4(+) 'type I' AL, with a multilobula ted nucleus resembling those of the abnormal cells in adult T-cell leu kemia (ATL), from a CD8(+) 'type II' AL, a large lymphocyte with basop hilic cytoplasm and a nucleus containing coarse chromatin. Type I AL w ere detected in 7 of 8 patients with Japanese encephalitis (JE), but i n none of Il patients with herpes simplex encephalitis (HSE) and none of 19 patients with unspecified acute viral encephalitis. Type II AL w ere seen frequently in all three groups. The observation of type I AL in CSF strongly suggests JE, which warrants careful follow-up without antiberpetic drugs. In identifying type I AL, which presumably are vir ally transformed lymphocytes, care must be taken to distinguish them f rom leukemic involvement by ATL cells, which frequently includes the m eninges. Both type I and type II AL also must be differentiated from l ymphoma cells. (C) 1998 Elsevier Science B.V. All rights reserved.