[Preparation of SOKT1-RTA immunotoxin and its specific cytotoxic effect on human T lymphocytes]

An immunotoxin, SOKT1-RTA, was prepared successfully by conjugating a murine anti-human T lymphocyte monoclonal antibody (McAb) SOKT1 and the ricin toxin A chain (RTA) with the heterobifunctional linker SPDP. At the presence of 20 mmol/L NH4Cl, the SOKT1-RTA conjugate killed 82% of the human peripheral blood T cells (PBT), and decreased their 3H-Leu incorporation to 6.2% of the untreated controls. The toxic effect of the immunotoxin can be partially blocked by unconjugated SOKT1, but not by an irrelevant McAb D51. These results indicated that the SOKT1-RTA conjugate still retains both functions of its component parts:binding to human PBT specifically, and inhibiting protein synthesis. It may be an effective reagent for in vitro depletion of immunocompetent T cells from human bone marrows.

[Influences of an anti-pan-T cell ricin A-chain immunotoxin on generation of human immunocompetent T cells and hematopoietic progenitor cells]

SOKT1 -RTA immunotoxin, which consisted of an anti-pan-T cell monoclonal antibody SOKT1 and ricin toxin A-chain, decreased the peripheral blood lymphocyte transformation in response to PHA and to alloantigen by 92.9% and 84.7%, respectively. The generation of allocytotoxic T cell was also dramatically inhibited by this immunotoxin. After treatment of human bone marrow mononuclear cells with the immunotoxin, erythroid proliferation in CFU-E test preserved 62.9%. Based on these findings, we concluded that SOKT1-RTA immunotoxin can effectively inactivate human T lymphocytes in vitro without serious toxic effect on the hematopoietic progenitor cells. It may be an effective agent in aGVHD prophylaxis.

Axonal signals regulate expression of glia maturation factor-beta in Schwann cells: an immunohistochemical study of injured sciatic nerves and cultured Schwann cells

Glia maturation factor-beta (GMF-beta) is a 17 kDa protein purified and sequenced from bovine brains. Using the monoclonal antibody G2-09 directed against GMF-beta, we previously demonstrated endogenous GMF-beta in astroblasts, Schwann cells, and their tumors in culture. In the present study, we have used indirect immunofluorescence microscopy with G2-09 to examine the effects of transection, crush, and regeneration of sciatic nerve on the expression of GMF-beta in Schwann cells in situ and to study the time course of GMF-beta induction in Schwann cells in vitro. For comparison, a parallel study was carried out with monoclonal antibodies directed against nerve growth factor (NGF) receptor. We found that (1) neither GMF-beta nor NGF receptor was detectable in intact sciatic nerves, (2) all Schwann cells of the distal segment of the transected nerve expressed GMF-beta as early as 3 d after axotomy that persisted up to 3 weeks, (3) axonal regeneration repressed the Schwann cell expression of GMF-beta, (4) isolated Schwann cells derived from rat sciatic and adult human sural nerves developed intracellular GMF-beta in culture following an initial lag period, and (5) the induction of Schwann cell NGF receptor coincided temporally with that of GMF-beta in the transected nerve and in culture. These results show that the expression of GMF-beta in Schwann cells, as is the case with the NGF receptor, is induced by the loss of the normal axon-Schwann cell contact. We propose that the induction of GMF-beta, as well as NGF receptor, in Schwann cells after nerve injury plays a role in axonal regeneration.

[Luteinizing hormone-releasing hormone (LRH) agonist in the treatment of breast cancer, osteosarcoma and prostate carcinoma--analysis of 12 patients]

This paper first reports the results of 12 patients with sex hormone-dependent neoplasms, including 9 women with breast cancer, 2 men with osteosarcoma and 1 man with prostate carcinoma, treated by LRH agonist, (D-Ala6, des-Gly-NH2(10))-LRH-ethylamide (LRH-A) 100-200 micrograms, IM, QD. After 15-30 days of administration, the concentrations of plasma mean estradiol, progesterone, testosterone, serum luteinizing hormone and follicle-stimulating hormone were lowered significantly in the peripheral blood of all patients, associating with improvement of the patients' general condition and reduction of the tumors and/or metastatic foci. No serious side effects were observed except vaginal irregular bleeding in isolated patients. Three patients died and the others were alive in follow-up of 4-30 months. The results suggest that LRH-A be useful in the treatment of the sex hormone-dependent tumors and worth further study.