| Abstract: | Tubuloreticular inclusions (TRI) developed within the endoplasmic reticulum of peripheral blood mononuclear cells (PBMC) sampled from eight patients with chronic type B hepatitis during cycles of therapy with DNA-recombinant human alpha-interferon (rIFN alpha A). Each cycle of therapy consisted of a series of six intramuscular injections (triweekly) of a fixed dose of rIFN alpha A (from 18 to 68 X 10(6) IU/dose). In PBMC examined by transmission electron microscopy, TRI were absent prior to therapy and developed during therapy in all cases. Peak serum levels of alpha-interferon (320 to 960 IU/ml) were achieved within 12 hours. At 24 hours. TRI were detected in 0.5 to 6.5% of PBMC sections, and they persisted in 1.4 to 6.8% of sections examined at 48 hours. After five sequential interferon doses, TRI were observed in 1.6 to 9.8% of PBMC sections. TRI could no longer be detected at 5 to 16 days after cessation of rIFN alpha A, but they reappeared during subsequent cycles of therapy. Subpopulations of the PBMC with TRI were differentiated by immunoelectron microscopy utilizing a battery of anti-Leu monoclonal antibodies: surface markers of T cells, helper/inducer or cytotoxic/suppressor T cell subsets, natural killer cells, or B-cells were identified by direct or indirect procedures utilizing avidin and biotinylated peroxidase. In cases analyzed with multiple monoclonal antisera, TRI were expressed in all of the major PBMC subpopulations. Monocytes with TRI were demonstrated by the endogenous peroxidase reaction. TRI were not found in circulating polymorphonuclear granulocytes. Lymphocytes isolated from healthy donors and exposed to rIFN alpha A (100 IU/ml), for 48 to 72 hours in vitro, developed TRI in proportions of PBMC sections (2.3 to 8.4%) comparable to those observed in the interferon-treated patients. Stimulation of lymphocytes with concanavalin A, for 72 hours before rIFN alpha A exposure, enhanced formation of TRI which could then be found in T blasts. Stimulation of donor lymphocytes with Sendai virus, a potent inducer of alpha-interferon, also resulted in formation of TRI by 48 hours. This suggested that lymphocytotrophic virus infections could exercise a primary role in the natural pathogenesis of TRI. |
