The phenotypic and molecular characterization of Nb2 lymphoma cells activated with IL-2 and human growth hormone

The Nb2 rat lymphoma cell line has the unique property that its growth is dependent on lactogenic pituitary hormones. Cell surface staining with monoclonal antibodies showed expression of class I MHC alloantigens of the RT1u haplotype, but no expression of class II MHC antigens. Staining for differentiation markers was strongly positive with antibodies OX52, W3/13 and OX44. Partial and weaker staining was obtained with CD2, P4/16 and the transferrin receptor. Nb2 cells were negative with CD5, OX40 and CD4, whilst CD8 stained only a minor fraction (1%) and certain variant clones of the cell line. This general pattern of staining is consistent with the phenotype of a small subpopulation of immature T cells. Nb2 cells proliferated in response to recombinant human IL-2, although they did not stain with antibodies against the IL-2 receptor. Enhancement of the stimulation by IL-2 in the presence of a submitogenic concentration of hGH indicated a synergism between these two hormones, and responses were suppressed by a similar dose of cyclosporin A (ID50=2 microg/ml). Although IL-2 could not be identified in culture supernatants, the presence of mRNA for IL-2, IL-2R and IL-4 was demonstrated by dot blot analysis. Finally, evidence that the Nb2 lymphoma is of T-cell lineage was given by Northern blot detection of mRNA for the alpha and beta chains of the T-cell receptor.