Quantitative analysis of cytotoxicity induced by HTLV-I carrying cells against a human lymphoblastoid cell line, Molt-4.

Co-cultivation of HTLV-I carrying cells and virus-free lymphoid cells resulted in the cytopathic effect and cytotoxicity of the latter cells. Microscopically, these phenomena were observed as early as 2 h as the appearance of multinuclear giant cells and ballooning cells with striking resemblance with cytopathic changes induced by HTLV-III. When the cytopathic effect and cytotoxicity of the target cells by HTLV-I carrying cells were assayed by 51Cr-release assay system, these phenomena were quantitatively analysed and the cytotoxic activity was observed generally in HTLV-I positive cells. Virally induced cytotoxicity was inhibited by plasma of adult T-cell leukemia (ATL) patients specifically. Cytotoxic activity of HTLV-I positive cell lines was correlated with HTLV-I antigen expression of them. HTLV-I negative cell lines did not express cytotoxicity significantly.