Profile: Cambridge Biotech Corporation focuses on the development, manufacture and sale of diagnostic kits for use in the diagnosis of diseases caused by retroviruses. We focus on the use of fixed autologous stimulator cells to correctly present human immunodeficiency virus type I viral peptides to nonhuman primate lymphocytes in proliferation and cytotoxic T-lymphocyte assays. Autologous, virus-transformed lymphoblastoid cell lines were established by using peripheral blood lymphocytes from rhesus monkeys that were previously immunized with recombinant human immunodeficiency virus type I glycoprotein 160. These autologous cell lines were used to present human immunodeficiency virus type I viral antigens in a processed and cell-associated manner to T lymphocytes. This was done by either infecting the cells with recombinant vaccinia viruses or pulsing them with synthetic peptides and then subjecting them to a mild fixation step with glutaraldehyde. Fixed antigen-presenting cells were then used as stimulator cells in vitro to measure cell-mediated immune responses. Both the vaccinia virus-infected and peptide-pulsed autologous cells stimulate antigen-specific cellular proliferative responses. The magnitude of the responses correlates with the immunization histories of the animals and other measures of immunity such as antibody titers. Autologous vaccinia virus-infected cells are also capable of inducing the in vitro maturation of CD4+ and CD8+ precursor cytotoxic T lymphocytes into antigen-specific mature cytotoxic T lymphocytes. The use of stimulator cells to present viral peptides in a cell-associated manner appear to be a very sensitive to measure cell-mediated immune responses with peripheral blood lymphocytes from non-human primates. A similar approach will function with peripheral blood lymphocytes from humans.