Effect of serum fractions obtained from cancer patients by double filtration plasmapheresis combined with natural tumor necrosis factors and cyclophosphamide on murine pulmonary metastases.

We investigated the effects of fractionated sera obtained from cancer patients by double filtration plasmapheresis (DFPP) plus antitumor agents on murine pulmonary metastasis. Fractions of the sera, in combination with natural human tumor necrosis factors (nTNF) and cyclophosphamide (Cy), were systemically administered to Lewis lung carcinoma-bearing mice. When the second filtrate (a plasma fraction containing substances composed of smaller molecular weight compounds) combined with low-dose nTNF (1,000 U/kg) and Cy (250 micrograms/kg) was administered to the mice, the degree of metastasis was significantly suppressed compared with the control group (p less than 0.01). In contrast, the discarded fluid (a plasma fraction containing larger molecular weight compounds) combined with the same doses of nTNF and Cy caused little inhibition of metastasis. Also, the discarded fluid significantly suppressed natural killer activity compared with normal sera (p less than 0.01). The results suggested that DFPP combined with nTNF and Cy is an efficient procedure to remove immunosuppressive factors from the sera of cancer-bearing hosts, to enhance the host antitumor immunity, and to suppress tumor proliferation.