Accumulation of enriched ²³⁵U-UO₂F₂ in the body had injurious effects on the immune function of central and peripheral immune cells. After an intravenous injection of ²³⁵U-UO₂F₂, the spontaneous ³H-TdR incorporation in thymocytes and bone marrow cells decreased, with the thymocytes damaged more markedly. The proliferation ability of spleen T and B lymphocytes were both inhibited, with B lymphocytes inhibited more severely. In spleen B lymphocytes the IL-1 production and IL-2 consumption were diminished. The inhibition of spleen B lymphocyte proliferation by ²³⁵U-UO₂F₂ was partially restored by adding exogenous IL-1 or IL-2 to the cultured lymphocytes obtained from ²³⁵U injected mice.