Rat thymic epithelial cells (TEC) in long-term culture were characterized by anticytokeratin monoclonal antibodies (mAbs) and electron microscopy. Phenotypic analysis performed by a large panel of mAbs showed that the highest percentage of these cells was of the subcapsular/medullary type. Recombinant rat interferon (IFN)-gamma up-regulated class-I and class-II MHC expression by TEC in culture as confirmed by immunohistochemistry and flow cytometry, but did not significantly alter other cell markers. TEC supernatants of IFN-gamma- treated cultures showed higher interleukin-6 (IL-6) activity, compared to the control, as determined by proliferation of the IL-6-sensitive B9-cell line. Increased IL-6 activity was probably not a consequence of increased TEC number in IFN-gammatreated cultures because IFN did not significantly stimulate TEC proliferation in vitro. In contrast, IL-6 significantly stimulated TEC proliferation, indicating that this cytokine is not only a regulatory molecule for T-cell proliferation, but could also be an autocrine growth factor for thymic epithelium.

An anti-idiotypic IgGlκ murine monoclonal antibody (MoAb) Y7 against purified monoclonal IgMλl, derived from a patient with Waldenström’s macroglobulinemia, has been generated. This antibody cross-reacted with the tumor-derived idiotypes of patients with B cell nonHodgkin’s lymphoma as measured by competitive inverse solid radioimmunoassay using unpurified serum samples. Our results with the inhibition curves of 10 sera of normal donors and 60 sera of lymphoma patients indicate that 21 lymphoma patients revealed cross-reactivities > 7%, the mean value observed in normal donors. Of these, 5 sera cross-reacted strongly, in the range of 43–163%, revealing a frequency of positive cross-reactivity for MoAb Y7 of 1/12 sera of lymphoma patients. The generation of a panel of anti-idiotypic antibodies which cross-react with different tumor-derived Ig in serum may be valuable for monitoring the disease in a high proportion of NHL patients.

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