Characterization of the specificity of a naturally-occurring monoclonal anti-thymocyte autoantibody derived from an unimmunized, neonatal Balb/c mouse.

The immune repertoire of healthy unimmunized Balb/c mice contains a significant proportion of B lymphocytes which produce natural autoantibodies. The majority of these predominantly CD5+ B lymphocytes, secrete autoantibodies which react with conserved intracellular autoantigens such as actin, myosin and DNA. Significantly fewer autoreactive B lymphocytes produce natural autoantibodies reactive with cell surface autoantigens. In the present study, the specificity of monoclonal IgM kappa anti-thymocyte autoantibodies from hybridoma NMT-1 (NMT-1 maAbs), derived from the spleen of an unimmunized 8-day-old inbred Balb/c mouse has been examined. Anti-thymocyte NMT-1 maAbs reacted with cell surface molecules on 86-87% thymocytes from mice 1-28 days of age. Thymus-restricted expression of the identified autoantigen was demonstrated by the lack of detectable reactivity of NMT-1 maAbs to cell surface molecules of Balb/c mouse splenocytes, PBLs, lymph node, peritoneal and bone marrow cells and tissues including brain, liver and kidney. Furthermore, multiparameter flow cytometry demonstrated an association between the expression of the cell surface autoantigen identified by NMT-1 maAbs and thymocyte maturation as 94-97% of the CD4+ CD8+ thymocytes expressed the identified autoantigen which was largely absent from CD3+ thymocytes and not expressed in the peripheral immune system. Tissue distribution, flow cytometry and competition analysis indicated differences between identified T lymphocyte markers, including Thy-1, and the autoantigen identified by NMT-1 maAbs in this study. Immunoprecipitation analysis, however, revealed that NMT-1 maAbs reacted with 14.5 and 18.3 kDa Thy-1-related autoantigens within Balb/c mouse thymocyte membrane extracts, possibly unique glycosylated forms of the Thy-1 molecule.

Pharmacokinetics, tissue distribution, and cell localization of [35S]methionine-labeled recombinant human and murine alpha interferons in mice.

The pharmacokinetics, tissue distribution, cell localization, and penetration into tumor xenografts of recombinant [35S]methionine-labeled human alpha interferon (HuIFN-alpha) and murine alpha interferon (MuIFN-alpha) were examined in mice. Both interferons (IFNs) were removed from the blood in a rapid biphasic manner; HuIFN-alpha was cleared faster than MuIFN-alpha. Tissues were analyzed for radioactivity and over 90% of the IFNs was accounted for. The IFNs were detected predominantly in liver, kidney, gastrointestinal tract, pancreas, spleen, and lung. The levels of MuIFN-alpha compared with HuIFN-alpha were greater in the liver, spleen, and lung and less in the kidney, pancreas, and gastrointestinal tract. Heart, brain, testes, thymus, lymph nodes, fat, skin, and skeletal muscle contained much lower but measurable levels of both IFNs. There was penetration of HuIFN-alpha into tumor xenografts. The pharmacokinetics of IFN-alpha were independent of the strain of mouse, BALB/c or CBA, immune deprivation, or the presence of a tumor xenograft. Autoradiography of tissue sections from mice given injections of HuIFN-alpha or MuIFN-alpha indicated focal radioactivity in proximal convoluted tubules in the kidney and diffuse radioactivity in the liver, gastrointestinal tract, and pancrease. MuIFN-alpha, but not HuIFN-alpha, showed intense localization in cells in hepatic sinusoids, marginal zones in the spleen, and pulmonary alveolar walls, suggesting uptake by cells of the monocyte/macrophage lineage in these sites. The study shows the utility of biosynthetic labeling for pharmacokinetic studies of cytokines, clear differences in tissue distribution of IFN-alpha according to its species of origin, and targeting of homologous IFN-alpha to cells of the monocytic lineage.