Tumor-infiltrating B-cell-derived IgG recognizes tumor components in humanlung cancer

Tumor-infiltrating lymphocytes consist predominantly of T cells, whereas B cells, plasma cells, and natural killer cells are observed with different d egrees of frequency. We investigated the nature of tumor-infiltrating B lym phocytes (TIB) in human lung cancer First, to examine the ability of immuno globulin production by TIB, cancer tissues were subcutaneously transplanted in severe combined immunodeficient mice, and the murine serum was examined for the concentration of human immunoglobulin. Human IgG (hulgG) was detec ted in the serum of all 12 mice engrafted with lung cancer tissues. hulgM a s almost undetectable. The levels of human reached a peak approximately, 6 weeks after engraftment and gradually decreased hilt were detectable until 20 weeks postengrafment. Serum from a large cell carcinoma-engrafted mouse reacted with a protein of 60 kDa derived from lung cancer cell lines (FC-9, Sq-1) and autologous tumor cells but did not react with cell lysates of no rmal lung tissue. Serum from an adenocarcinoma-engrafted mouse reacted with two proteins, 33 and 55 kDa, derived from lung cancer cell lines (PC-9, Sq -1, A549) and autologous tumor cells but did not react with the lysate of n ormal lung tissues. These results suggest that B cells infiltrating lung ca ncer tissue produce IgC that recognizes common tumor-specific antigen.