Clusters of Burkitt's lymphoma cells adhere to and proliferate on HIV-1–infected MVEC from autologous human BM (A) and heterologous human brain (C) but not on uninfected brain MVEC (B). (A) Lymphoma cells and stromal cells in (A) were derived from the BM of an HIV-1 seropositive lymphoma patient. The lymphoma cells were EBV⁻, contained a t(8;14) chromosomal translocation, and proliferated spontaneously in stromal cell cultures that supported MVEC survival. (B) Lymphoma cells from (A) were transferred to pure brain MVEC monolayers. A small percentage of lymphoma cells adhered to brain MVEC, but these brain MVEC did not support sustained adhesion and growth of lymphoma cells. (C) Lymphoma cells from (A) were transferred to pure brain MVEC monolayers infected with HIV-1. Infected MVEC supported the long-term adherence and growth of lymphoma cells.