Sustained TL1A expression modulates effector and regulatory T-cell responses and drives intestinal goblet cell hyperplasia.

The tumor necrosis factor (TNF) superfamily protein TNF-like 1A (TL1A) is the ligand for death receptor 3 (DR3). TL1A is induced on activated dendritic cells (DCs) and its expression has been linked to human inflammatory bowel disease. To address how TL1A might influence intestinal inflammation, we generated transgenic mice that constitutively express TL1A on DCs. TL1A transgenic mice developed striking goblet cell hyperplasia in the ileum that was associated with elevated interleukin (IL)-13 levels in the small intestine. IL-13- and IL-17-producing small intestinal lamina propria T cells were increased in TL1A transgenic mice. TL1A also enhanced regulatory T (Treg) cell turnover in vivo and directly stimulated Treg cell proliferation in vitro. The presence of TL1A attenuated the ability of Treg cells to suppress conventional T cells, an effect that required DR3 signaling in either conventional T cells or Treg cells. Our findings identify mechanisms by which chronic DR3 signaling could promote pathogenesis in inflammatory bowel disease.

Soluble factor and cell-cell interaction in cytostasis induced by bone marrow cells.

Cell-cell interaction and soluble low-molecular-weight products are probably involved in in vitro inhibition of leukemic cell growth by bone marrow cells.

Characterization of erythroid cell-derived natural suppressor activity.

Nucleated erythroid cells (NEC) have been previously reported to the capable of suppressing antibody-mediated primary (IgM) and secondary (IgG) immune responses to thymus-dependent antigens. In the present study we indicated that NEC, separated from the spleens of mice following phenylhydrazine treatment were able to suppress directly the proliferative response of preactivated B cells to lipopolysaccharide (LPS) in vitro. While being active in suppressing B cell blastogenesis, NEC, however, failed to reduce both cell proliferation and cytotoxic T lymphocyte (CTL) generation in an allogeneic mixed lymphocyte culture (MLC). NEC also lacked a significant effect on interleukin (IL)-2 production and utilization by concanavalin A (Con A)-activated T lymphocytes. The NEC-derived suppression of B cell proliferation was, at least in part, mediated by soluble molecules. The specific blockade of transforming growth factor (TGF)-beta synthesis with antisense oligodeoxynucleotides (OD) binding TGF-beta mRNA, as well as the neutralization of TGF-beta activity with anti-TGF-beta antibodies (Ab), resulted in a detectable diminished ability of the NEC-conditioned medium (CM) to suppress B cell blastogenesis. Taken together, the results suggest that: 1) NEC may suppress directly B cell responses, while not affecting T cell ones; 2) NEC may mediate their natural suppressor (NS) activity partially through releasing TGF-beta.

A role for interferon-gamma and transforming growth factor-beta in erythroid cell-mediated regulation of nitric oxide production in macrophages.

Interferon-gamma (IFN-gamma) and transforming growth factor-beta (TGF-beta) are known to be a potent inducer and inhibitor for macrophage (Mo) activation process, respectively. In the present study we established that the nucleated erythroid cells (NEC) separated from the spleens of adult (CBA x C57BL/6)F1 (CBF, H-2k/H-2d) mice following phenylhydrazine treatment are potentially capable of inducing nitric oxide (NO) production in thioglycollate broth-elicited peritoneal macrophages (Mo). The stimulating effect of both NEC and their culture supernatant on NO secretion by Mo was most apparent in the presence of bacterial lipopolysaccharide (LPS) and neutralizing antibodies (Abs) to TGF-beta and was largely reversed by the addition to the culture of neutralizing Abs to IFN-gamma. Collectively these results suggest that NEC, through production of IFN-gamma and TGF-beta, may exert a regulatory influence on development and functionality of cells pertaining to monocyte (Mc)/Mo lineage.

Tumor growth inhibitory and natural suppressor activities of murine bone marrow cells: a comparative study.

The murine bone marrow (BM) cells having a certain phenotypic similarity to null natural suppressor (NS) cells have been previously established to be able to inhibit in vitro leukemic cell growth in a genetically unrestricted manner. In this study we found that the treatment of normal (C57BL/6 x DBA)F1 BM cells with a lysosomotropic agent, L-leucine methyl ester (LME), largely abrogated their ability to reduce both P815 mastocytoma and L1210 lymphoma cell proliferation, as well as their NS activity tested for suppression of mitogen (Con A or LPS)-driven spleen cell proliferation. However, after being depleted of the cells binding wheat germ agglutinin (WGA), the BM cells maintained tumor growth-inhibitory activity, while demonstrating no significant NS activity. Moreover, in contrast to T-cell blastogenesis-inhibitory NS activity of BM cells, that was greatly reduced by the addition into the culture of either neutralizing anti-interferon (IFN)-gamma antibody (Ab) or NG-monomethyl-L-arginine, a competitive inhibitor of NO synthase, natural antitumor cytostatic activity of BM cells was not found to be dependent on the presence in medium of IFN-gamma and to be associated with NO production. When incubated at suboptimal numbers with tumor cells on conic, round, and flat well bottoms for 7 h, BM cells provided the most, middle, and least (or no) tumor growth inhibition, respectively, suggesting, thereby, a significance of cell density in cytostatic process. It was also found that the BM cells cultured for 20 h with the medium conditioned by mitogen-preactivated T or B lymphocytes were significantly more suppressive to tumor cell proliferation than the BM cells cultured in medium alone. The potentiation of BM-cell cytostatic activity by T-cell-conditioned medium (CM), but not that by B-cell-CM, was found to be partially reversed by anti-IFN-gamma Ab. Finally, a noticeable tumor growth-inhibitory activity, which could be significantly enhanced upon T-cell-CM, was shown to be also attributable to BM cells from athymic BALB/c mice. Taken together, the results suggest that (1) the tumor growth inhibitory BM cells and the NS BM cells are not identical in their cell compositions, but also differ in their mechanisms of antiproliferative action; (2) a contact cell-to-cell interaction may play a significant role in BM-cell-mediated tumor growth inhibition; (3) the activated lymphocytes, through both IFN-gamma-mediated and IFN-gamma-independent pathways, are able to operatively up-regulate the cytostatic activity of BM cells; and (4) the tumor growth-inhibitory activity exhibited by the normal unmanipulated BM cells, at least in its significant part, may not be a consequence of thymus-dependent immune processes occurring normally in the body.