Ultrastructural study of type C virus particles in phytohemagglutinin-stimulated lymphocytes from healthy adults seropositive to adult T-cell leukemia-associated antigens.

PHA-stimulated peripheral lymphocytes from six healthy adults consisting of four family members of an adult T-cell leukemia (ATL) patient and two blood bank donors, seropositive to ATL-associated antigens (ATLA), were all positive for the expression of ATLA and ATL-associated virus (ATLV). These results revealed that anti-ATLA-positive persons were healthy carriers of ATLV and that the numbers of ATLV observed in each culture were more proportional to the percentage of ATLA-positive lymphocytes than anti-ATLA titers of each person. Virus particles detected were C-type in morphology, and essentially similar to those observed in MT-2 and other ATL-related cells, but rather uniform in size, mostly 120-130 nm in diameter. Furthermore, it is of interest that tubuloreticular structures and striated fusiform structures, which were found in fresh or short term cultured ATL cells, were observed in some cultures of lymphocytes from anti-ATLA-positive healthy persons.