[Plaque-forming cell (PFC) technique in the assay of serum blocking activity in lung cancer]

The serum blocking activity of 32 patients with lung cancer was assayed by means of PFC technique and half-hemolysis concentration (HC50) test. The results showed that the serum from lung cancer patients had an obvious immunosuppressive effect on antibody production of C3H mice. The PFC number of mice which had received an injection of serum from lung cancer patient was significantly lower than that of the control group which was given an injection of 0.9% saline solution (47.3 +/- 2.9, 89.8 +/- 6.9, P less than 0.01). The serum from patients with various benign lung diseases and healthy adults did not show such immunosuppressive effect (86.5 +/- 8.6, 75.7 +/- 6.0). The results examined by HC50 test also indicated that the antibody level of mice injected with the serum from lung cancer patients was obviously lower than that of control mice (56.3 +/- 3.0, 82.09 +/- 5.0, P less than 0.01). The immunosuppression incidence of serum from lung cancer patients (16/32) was significantly higher than that of serum from patients with benign diseases (3/19) or from healthy adults (2/18). The positive rate of the serum blocking activity in lung cancer patients was 50% which was significantly higher than that of the other two groups. There was no correlation between the immunosuppressive activity and stage or histologic classification of lung cancer. It was also found that higher incidence of immunosuppressive activity was present in the early lung cancer. The result suggests that the serum immunosuppression test using PFC technique be valuable in the early diagnosis of lung cancer.