In Vitro and In Vivo Studies of a 2,4,6-Trinitrophenyl {TNP)-Binding Immunoglobulin A (IgA) Lymphoma Isolated From MOPC-315, a TNP-Binding IgA Plasmacytoma of BALB/c Mice23

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Abstract
The cells of 315/P, a long-passaged in vitro line established from the BALB/c plasmacytoma MOPC-315, appeared to be arrested at a preplasmacytic level of development in vitro. Studies were conducted to determine if differentiation of 315/P cells might be influenced by in vivo conditions. Differentiation of immunoglobulin expression was monitored by detection of the anti-2,4,6-trinitrophenyl antibody activity of M315, the immunoglobulin produced by MOPC-315. Tumors that developed after sc injection of 1-2×107 315/P cells were compared to 315/+ tumors (MOPC-315 passaged continuously in vivo) for M315 expression and a number of growth properties. In contrast to wild-type (315/+) tumors, none of the 315/P tumors contained cells that formed indirect hemolytic plaques with 2,4,6-trinitrophenylated sheep erythrocytes; however, 315/P cells continued to express cytoplasmic and cell-surface membrane M315. Immunoglobulin expression by 315/P cells in vitro and through eight transplantation generations in vivo was therefore more typical of an IgA lymphoma than a plasmacytoma. Furthermore, when 315/+ and 315/P tumors were compared, striking differences were also observed in: a) cytologic and ultrastructural features, b) growth potential in different anatomic sites, c) tumorigenicity, and d) the occurrence of M315-bearing lymphocytes in the circulation. These studies demonstrated that a clonal murine B-cell neoplasm may express strikingly dissimilar morphologic, immunologic, and clinical phenotypes, and it was concluded that 315/P cells may provide unique advantages in: 1) studies on the mechanisms regulating the differentiation of normal and neoplastic B-cells and 2) structural studies of a cell-surface membrane immunoglobulin whose secreted form has already been extensively characterized.