Immunoactive products of placenta. V: Soluble factors from murine placenta can block effector stages of maternal antipaternal cell-mediated immunity

A placenta-derived suppressor factor with a T-cell bias

PROBLEM

Functional and mechanistic aspects of immunosuppression by murine placental supernatants (MPS) were investigated.

METHOD OF STUDY

MPS and a low molecular weight fraction of the supernatant (MPSf) were tested for suppressive action on T-cell reactivity in vitro and in vivo, on B-cell responses and on T-cell activation events.

RESULTS

MPS and MPSf suppress mitogen-induced proliferation and mixed lymphocyte reactions of human and murine lymphocytes, antigen-induced proliferation of T cells in vitro and in vivo, proliferation of CD8+ lymphocytes, proliferation induced by cross-linking of surface CD3 and the in vivo response of mice to allogeneic stimuli. MPSf affects cell cycling of activated T cells and blocks interleukin (IL)-2 production. MPSf does not affect antibody production or the induction of MHC class II expression on B cells.

CONCLUSIONS

MPSf is a potent inhibitor of T-cell responses in vitro and in vivo, with no demonstrable effect on B-cell function.

A murine model of NK cell mediated resorption

There is increasing evidence that some models of immunologically mediated murine embryo demise involve nonspecific lytic effector cells. In this paper, we use two double stranded synthetic RNAs, known as potent interferon inducers and NK cell activators, the Poly (I). Poly (C) and the less toxic Poly (I). Poly (C12U). These polynucleotides enhance fetal resorption rates in both resorption prone and none-resorption prone strains of mice. We have studied the kinetics of the phenomenon, and observed an anti-implantation-like effect of early injection during early pregnancy. The abortifacient effects can be adoptively transferred to naive recipients by spleen cells from Ds RNA injected donors. Such effects are abrogated if the cells are pretreated with anti-NK cell antiserum. The relevance of these findings to the survival of the conceptus is suggested.

Recombinant human beta-galactoside binding lectin suppresses clinical and histological signs of experimental autoimmune encephalomyelitis

Human placental tissue contains regulatory molecules that may prevent allo-sensitization. Recently, a 14 kDa beta-galactoside binding protein with demonstrated immunoregulatory properties has been cloned using cDNA from human placenta and expressed in Escherichia coli. The present study assesses the ability of this recombinant immunomodulatory lectin (rIML-1), to prevent experimental autoimmune encephalomyelitis (EAE), a paralytic T cell-mediated disease directed against myelin basic protein (BP). Injection of rIML-1 into Lewis rats inhibited the induction of both clinical and histological signs of EAE, apparently by blocking sensitization of encephalitogenic BP-specific T cells and inducing BP-dependent suppressor cells. Because it is neither immunogenic nor toxic, rIML-1 may have application in humans, and would have distinct advantages over unselective cytotoxic immunosuppressive agents used currently in the treatment of autoimmune diseases and transplantation.

Natural killer (NK) cell activity of first trimester human decidua

The NK cell functional capacity of first trimester human decidua against K562 targets was assessed in a 3-hr CRA. Collagenase dispersal combined with plastic adherence, nylon wool passage, and density gradient centrifugation yielded NKH-1 (Leu 19) positive enriched decidual large granular lymphocyte fraction (mean 75% positive). Decidual effectors displayed reduced lytic activity compared with autologous PB effectors at every effector:target ratio but this difference in cytotoxicity was abolished by short-term culture before the CRA. Decidual effectors treated with 50 units rIL-2 showed increased lytic activity compared to untreated decidual cells. By FACS analysis the majority of NKH-1 positive decidual effectors were CD3 and CD16 negative which corresponds with a minority PB NK population. The implications of a population of functional NK cells in early pregnancy decidua for the materno-fetal relationship is discussed.