Effect of IgG produced by tumor-infiltrating B lymphocytes on lung tumor growth.

Tumor-infiltrating B lymphocytes (TIB) are often observed in lung cancer. The role of TIB in tumor growth has not been well investigated. Forty-four surgically-resected human lung cancer tissues were xenotransplanted into SCID mice. Their blood was collected and the volume of the transplanted tumors was measured regularly. The correlations between the IgG titer in the sera and the growth of the transplanted tumors according to the clinicopathological variables were examined. Human IgG production from TIB was observed in the all xenotransplanted mice. Twenty-seven out of the 44 tumors regressed gradually. The average serum human IgG level of the tumor regressors (n = 10) was significantly higher than that of the progressors (n = 9) in squamous cell carcinoma (p = 0.02), while there was no significant difference in the other histological groups. IgG produced by TIB might play a crucial role in preventing tumor growth in squamous cell carcinoma.