Accessory cells support adherence and growth of poorly differentiated neoplastic pre-B cells (BL). Dendritic cells,95 CD4⁺ T cells,34 and other auxiliary cells (Aux)97 infected with HIV-1 or exposed to gp120 or gp160³⁴ release IL-6, a potent mitogen for lymphoma cell growth. Lymphoma cells themselves, both those infected with EBV and EBV⁻, release IL-10 in an autocrine fashion. MVEC infected with HIV-1 express CD40 and bind to lymphoma cell CD40L, a process that activates VCAM-1 expression and subsequent binding with its cognate ligand VLA-4.135Proliferation and survival of lymphoma cells is enhanced following adherence to MVEC. Adherence to MVEC may also facilitate retention of BL cells at sites rich in auxiliary cells for exposure to IL-6.