Resting peripheral blood mononuclear cells (PBMC) or purified T-cells can be induced to proliferate when cocultured in vitro with fixed HTLV- infected T-cells. This process of HTLV-dependent cellular activation and induction of proliferation has been considered distinctive because of an apparent independence from conventional T-cell costimulatory signals. We have examined several HTLV-infected cell lines and found that proliferation was readily induced in resting PBMC by T-cells that were productively-infected with HTLV. However, equivalent HTLV-productive infection in a B-cell line failed to induce proliferation in PBMC, suggesting that HTLV-dependent induction of proliferation in PBMC was, at least in part, dependent upon a T- cell-specific signal. Furthermore, the induction of proliferation in PBMC populations was found to overlap with, and actually require, transfer and establishment of HTLV infection within the T-cell compartment of the PBMC population. These findings suggest that virus-induced activation of target cells may be directly associated with transfer and spread of HTLV infection.
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We thank our colleagues Dr. Eliane Meurs, Dr. Peter Plagemann, Dr. Sarka Southern, and Bob LeVasseur for advice and constructive criticism during the course of these studies and Tim Leonard for skillful assistance in preparation of the figures. This work was supported in part by funds provided by the NIH. T.C.M. was the recipient of predoctoral support from Public Health Service Training Grant CA 09138.