Journal of General Virology, Vol 78, 2565-2574, Copyright © 1997 by Society for General Microbiology
Interleukin 4 stimulates infection and temporary growth of human neonatal lymphocytes exposed in vitro to human T-lymphotropic virus type I, but fails to substitute for interleukin 2 in the immortalization of infected cultures
A Mastino, S Grelli, C Favalli, C Matteucci, M De Carli, E Garaci and B Macchi
Institute of Microbiology, Faculty of Science, University of Messina, Italy.
It has been shown that interleukin 4 (IL-4) stimulates the proliferation of
cells from patients affected by adult T-cell leukaemia, the haematological
malignancy aetiologically associated with human T-lymphotropic virus type I
(HTLV-I). In the present study, human neonatal lymphocytes were exposed to
HTLV-I in vitro in the presence of IL-4. The results showed that: (i)
cultures exposed to HTLV-I in the presence of either IL-4 or IL-2 bound
IL-4; (ii) IL-4 did not substitute for IL-2 as a growth factor in cell
lines previously infected and maintained in IL-2; (iii) cultures exposed to
HTLV-I and maintained in IL-4 or IL-2 became infected; and (iv) IL-4
sustained the growth of HTLV-I-infected cultures for a maximum of 14 weeks.
Moreover, HTLV-I-infected cultures grown in IL-4 showed upregulation of the
IL-4 message and lower expression of HLA-DR and CD25 when compared with
counterpart cultures maintained in IL-2. These results suggest that
continuous growth of T-lymphocytes induced in vitro by HTLV-I infection, at
least temporarily, requires signals specifically provided by IL-2 and not
by IL-4.
