Immunoglobulin secretion by cell lines derived from African and American undifferentiated lymphomas of Burkitt's and non-Burkitt's type.

As part of an investigation of the cellular origins of undifferentiated lymphomas of the Burkitt's and non-Burkitt's types, we have examined immunoglobulin secretion by cell lines and biopsy samples from these tumors and have compared it with other lymphoblastoid cell lines. The majority of American lymphoma cell lines and a smaller fraction of African lymphoma cell lines secreted monoclonal IgM. No other Ig classes were secreted. Ig secretion by the tumor samples was also found to be exclusively IgM. The secreted IgM was polymeric and associated with J chain. Secretion of free light chain by most of the tumor cell lines was observed. Quantitation by immunoassay demonstrated that the American lymphoma cell lines secreted significantly more IgM than the African lymphoma cell lines. We have proposed that the lymphoma cells represent an early stage of B cell differentiation, during which antigen-independent secretion occurs.

Serum levels of fibronectin and a fibronectin-like DNA-binding protein in patients with various diseases.

The levels of fibronectin and the fibronectin-like, malignant disease-associated DNA-binding protein (MAD-2) were determined in sera from patients with various diseases. The levels of both proteins were elevated in most serum samples from patients with various types of cancer and in some patients with nonmalignant diseases. The highest levels of these proteins were found in patients with carcinomas of the breast and lung. A subset of the lung cancer patients with small cell carcinoma had either normal or depressed marker levels. The levels of fibronectin and MAD-2 varied concordantly in the different patient populations studied, which suggests that the serum levels of the fragment are directly proportional to the total amount of fibronectin in the serum.

Isolation and identification of a human serum fibronectin-like protein elevated during malignant disease.

A human DNA-binding protein, designated MAD-2, has recently been found to be elevated in the serum from patients with malignant diseases. MAD-2 has been purified approximately 500-fold from peritoneal and pleural fluids collected from cancer patients. Immunodiffusion studies have indicated that MAD-2 is immunochemically identical to human plasma fibronectin. The purified material has been resolved by sodium dodecyl sulfate gel electrophoresis into two major protein chains with molecular weights in the range of 200,000 to 210,000 in either the presence or absence of disulfide bond-reducing agents. These results suggest that MAD-2 is a fibronectin fragment which has been generated through proteolysis. A quantitative assay system capable of detecting ng quantities of MAD-2 has been developed and used to verify the presence of elevated MAD-2 levels in DNA-binding protein fractions isolated from the serum of individuals with malignant diseases.