Y. Cheng Smart

Early pregnancy factor: its role in mammalian reproduction—research review

An immunosuppressive early pregnancy factor associated with mammalian reproduction is currently attracting considerable interest. Research into its detection, site of production, distribution, immunosuppressive property, characterization, and application is in progress in a number of laboratories. This review aims to crystallize the current research findings and to identify significant areas for further investigation and application.

Castanospermine, an oligosaccharide processing inhibitor, reduces membrane expression of adhesion molecules and prolongs heart allograft survival in rats

Abstract The inhibition of intracellular oligosaccharide processing is a new approach to immunosuppression in allotransplantation. The net effect of such inhibition is reduction in the membrane expression of certain glycoproteins. Hence cellcell interaction in allorejection may be impaired in the presence of glycoprotein processing inhibitors because the expression of key ligand-receptor pairs of N-linked glycoproteins including adhesion molecules is inhibited. The aims of this study were to measure the immunosuppressive ability of castanospermine (CAST) in a rat heart allograft model, to measure its effect on membrane expression of adhesion molecules (LFA-1α, LFA-1β, ICAM-1), class I and class II MHC antigens and on other T cell associated molecules (CD4, CD8, CD39, CD45, W 3 13 ), to test its tolerogenic potential and its toxicity. Membrane expression of these molecules was measured by flow cytometry for single cells and by immunoperoxidase staining for the allograft. In grafted rats CAST significantly reduced the expression of LFA-1α on lymphoid cells in the thymus, lymph node, spleen and heart allografts, ICAM-1 expression on endothelial cells of the allograft vasculature, class I and class II MHC expression on lymphoid cells in the thymus, class II MHC expression on lymphoid cells in the allograft; and CD4, CD8, CD45 and W 3 13 expression on lymphoid cells in some organs. By contrast, in non-grafted rats CAST significantly upregulated expression of class I MHC and CD45 in the thymus, lymph node and spleen, ICAM-1 and CD4 on lymphoid cells in the spleen, but reduced expression of LFA-1α on lymphoid cells in the thymus. It also prolonged rat heart allograft survival in a dose-dependent manner and with limited testing was relatively non-toxic. In conclusion, CAST is an immunosuppressive molecules which may work by downregulation of the ligand-receptor adhesion molecule pair, LFA-1α-ICAM-1 although subtle downregulation of class I and II MHC, CD4 and CD8 molecules could also contribute to its immunosuppressive activity. Hence, both lymphocyte-endothelial cell binding and lymphocyte activation may be inhibited by CAST. This work suggests that CAST may hold significant potential as a transplant immunosuppressant probably as an adjuvant agent to inhibitors of interleukin 2 secretion.

Early pregnancy factor as a monitor for fertilization in women wearing intrauterine devices.

Measurement of early pregnancy factor (EPF) by the rosette inhibition test was performed on serum samples from 14 women using intrauterine devices (IUDs). Serial blood samples taken during the luteal phase of 23 cycles demonstrated in six of the cycles a transient appearance of EPF during the 6- to 8-day period following ovulation. In contrast, no EPF activity was found in sera obtained from women in whom fertilization was prevented, either by sexual abstinence or tubal ligation. These observations support the postulate that the IUD functions by the prevention of implantation of the fertilized ovum, rather than by preventing fertilization.

LY-6C+ natural T (NT) cells mediate immune surveillance against NK-sensitive and NK-resistant transplantable tumours in certain strains of mice

We have previously shown that anti‐Ly‐6C monoclonal antibody (MAb) 2B6‐F2 identifies a subset of (CBA ± C57BL/6)F1 splenic NK‐1.1+ natural T (NT) cells which kill the NK‐sensitive YAC‐1 target in vitro. Furthermore, these Ly‐6C+ cells are responsible for 40–50% of in vitro YAC‐1 killing in all mouse strains tested. In BALB/c and DBA/2 mice, these cells killed not only YAC‐1 but also the NK‐resistant WEHI‐164 M1/16 target via a receptor that recognises a shared determinant on these targets in vitro. In the present study, the anti‐tumour role of Ly‐6C+ cells against the NK‐sensitive B16 melanoma and NK‐resistant tumours WEHI‐7 T lymphoma and WEHI‐164/1C fibrosarcoma was studied in vitro and in vivo. In vitro, B16, WEHI‐7 and WEHI‐164/1C tumour cell lines were highly sensitive to Ly‐6C+ cell killing. In vivo, these same tumours showed significantly increased growth when transplanted s.c. into syngeneic mice treated with 2B6‐F2 (0.05 ≤ p < 0.0005), and this was most marked in the first 15 days following tumour appearance, when tumours were <15 mm in diameter. Our results show that Ly‐6C+ cells play a role in controlling the growth of transplantable NK‐sensitive B16 melanoma, and in BALB/c mice, at least, the repertoire of susceptible tumours is extended to include NK‐resistant WEHI‐7 and WEHI‐164/1C. We conclude that Ly‐6C+ NT cells play a role in immunosurveillance against NK‐sensitive as well as NK‐resistant tumours in certain strains of mice.

Natural cell-mediated cytotoxicity (NCMC) against NK-sensitive tumours in vitro by murine spleen LY-6C+ natural T cells

Ly‐6C+ cells constitute 13 ± 3% of freshly isolated (CBA × C57BL/6)F1 mouse spleen leukocytes. Three distinct populations were identified: CD3ϵ+NK‐1.1− conventional T cells (6%), CD3ϵ−NK‐1.1− granulocytes (5%) and CD3ϵ+NK‐1.1+ T cells (∼ 2%). The CD3ϵ+NK‐1.1+ cells displayed a predominantly large granular leukocyte morphology and were the only Ly‐6C+ cell subset identified by MAb 2B6‐F2 to spontaneously lyse the NK‐sensitive YAC‐1 tumour in vitro. On further phenotypic analysis, these cells co‐expressed high levels of TCRVβ8. 1/8.2 and CD11b, moderate levels of CD90 and low levels of CD4 or CD8. The removal of CD4+ and CD8+ cells prior to Ly‐6C+ cell sorting showed that it was the CD4−CD8− double‐negative (DN) CD3ϵ+NK‐1.1+ T‐cell subset which was responsible for killing YAC‐1. These results indicate that we have identified a DN Ly‐6C+ subset of the recently designated NK‐1.1+TCRαβlow natural T (NT) cells, which are capable of natural cell‐mediated cytotoxicity (NCMC) against the NK‐sensitive YAC‐1 tumour in vitro. Additionally, these cells mediated the in vitro killing of 2 further NK‐sensitive tumours, murine B16 melanoma and human Jurkat T lymphoma. YAC‐1 and Jurkat expressed Fas and were susceptible to anti‐Fas MAb or rhuman Fas ligand (rhFasL)‐induced lysis. Furthermore, anti‐human Fas MAb M3 was shown to block sorted Ly‐6C+ splenocyte in vitro killing of Jurkat. In contrast, B16 did not express cell‐surface Fas and was resistant to anti‐Fas MAb‐induced lysis. Taken together, these results show that not only do Ly‐6C+ NT cells kill NK‐sensitive tumours in vitro but they mediate this activity via multiple cytotoxic mechanisms including Fas. Int. J. Cancer, 70:450–460, 1997.

The antitumor effects of levamisole in mice are mediated by NC-1.1+ cells

Abstract Murine natural cytotoxicity, which is a major component of the innate immune response in cancer, is mediated by leukocytes that express the NC-1.1 receptor. Mice depleted of natural cytotoxicity by treatment with an anti-NC-l.1 mAb show enhanced growth of certain transplantable tumors, so agents that enhance natural cytotoxicity by NC-1.1+ cells have the potential to be effective anticancer therapeutic agents. We have examined the immunomodulatory effect of levamisole on natural cytotoxicity mediated by NC-1.1+ cells against the BALB/c WEHI-164 murine fibrosarcoma. Administration of levamisole to BALB/c mice significantly enhanced in vitro splenic natural cytotoxicity against 51Cr-labeled WEHI-164 tumor cells. The effect was most marked 48 h after levamisole treatment, at a dose of 10 mg/kg body weight. This enhancement of natural cytotoxicity by levamisole could be completely abrogated by pretreatment of mice with an anti-NC-1.1 mAb. Treatment of BALB/c mice with 10 mg/kg levamisole significantly reduced the growth of WEHI-164 and this effect was abrogated by pretreatment of mice with anti-NC-1.1, indicating that the antitumor effect of levamisole was mediated, at least in part, via NC-1.1+ cells.

Studies on murine natural killer (NK) cells: V. Genetic analysis of NK cell markers

This paper attempts to clarify the number and nomenclature of murine natural killer (NK) cell specific alloantigens by defining the genetic relationships between them, that is, are they coded by loci which are independent, allelic, or linked. Strain typing and F2 analyses using five alloantisera (C3H X BALB/c)F1 anti-CE, CE anti-CBA, NZB anti-BALB/c, C3H anti-ST, and BALB/c anti-DBA/2 revealed that (a) the alloantigens NK-1.1 and NK-3.1 are determined by distinct loci which are linked on the same chromosomes, (b) the alloantigen NK-2.1 is determined by an independently segregating locus to those coding for NK-1.1 and NK-3.1, (c) the alloantisera, CE anti-CBA and NZB anti-BALB/c, which have been designated anti-NK-2.1 alloantisera recognize different alloantigens coded by independent genetic loci. Thus, these five alloantisera detect four NK cell specific alloantigens which, based on the chronology of their discovery, have been designated NK-1.1-(C3H X BALB/c)F1 anti-CE, NK-2.1-CE anti-CBA, NK-3.1-C3H anti-ST, and BALB/c anti-DBA/2 and NK-4.1-NZB anti-BALB/c.