Human helper T cell lines established by coculture of normal human cord leukocytes with an HTLV-II-infected rabbit leukocyte cell line (Ra-IIA).

Three helper T cell lines, designated CR-IIA (CR-IIA-1, CR-IIA-2, and CR-IIA-3), were established by coculturing normal human cord leukocytes with a lethally irradiated HTLV-II (human T-lymphotropic virus type II)-infected rabbit leukocyte cell line (Ra-IIA). CR-IIA had a normal human karyotype and expressed the surface markers CD3(+), CD4(+), CD8(-), CD19(-), CD25(+) and HLA-DR(+), confirming their helper T cell nature. CR-IIA cells were all free of Epstein-Barr virus nuclear antigen and were immunoreactive with serum samples from HTLV-I- or HTLV-II-infected patients and with anti-HTLV-I, p19 or p24 antibody. The provirus genome of HTLV-II was detected in these cell lines by the polymerase chain reaction combined with a digoxigenin-enzyme-linked immunosorbent assay. Electron microscopy of CR-IIA-1 cells revealed a few immature type C virus particles. These results suggest that HTLV-II was transmitted from the infected rabbit leukocyte cell line to human cord helper T lymphocytes with the development of immortalized HTLV-II-producing T cell lines.