Induction of allogenic T-cell hyporesponsiveness by galectin-1-mediated apoptotic and non-apoptotic mechanisms.

Galectin-1, a beta-galactoside-binding protein expressed at sites of T-cell activation and immune privilege, has shown specific immunosuppressive properties. Because of the implications of this protein in T-cell tolerance and its potential use to avoid graft rejection, we investigated the immunosuppressive effects of galectin-1 in the course of the human allogenic T-cell response. Galectin-1 induced a dose- and carbohydrate-dependent inhibition of the allogenic T-cell response. Addition of galectin-1 to alloreactive lymphocytes resulted in significant apoptosis of CD45R0-positive cells. This negative regulatory effect was accompanied by caspase activation, Bcl-2 downregulation and was prevented by addition of exogenous IL-2. In addition, a significant decrease of IFN-gamma production was detected in the non-apoptotic cell population, following exposure of alloreactive lymphocytes to galectin-1. Moreover, the immunosuppressive activity of this protein did not involve TGF-beta-mediated mechanisms. Since galectin-1 is expressed by activated T cells and could be acting by an autocrine negative loop to control human T-cell reactivity, we finally examined the regulated expression of this protein throughout the allogenic T-cell response. Expression of endogenous galectin-1 was detected at 24 h of cell culture, reaching its maximal levels after 72 h of allostimulation. The present study sets the basis for a potential use of galectin-1 as a selective immunosuppressive agent to limit T-cell-mediated reactivity during the effector phase of the alloimmune response.

Expression of SLAM as a functional and phenotypic marker in women with recurrent miscarriage.

In the present work, we investigated the Th1 and Th2 cytokine patterns secreted by infiltrating endometrial lymphocytes from fertile women and from patients with recurrent spontaneous miscarriage (RSM). Moreover, we also analyzed the expression of cytokines in the whole endometrium from fertile and RSM women. Furthermore, we investigated the expression of the activation marker signaling lymphocytic activation molecule (SLAM) a cell surface glycoprotein expressed on lymphocytes that upon engagement boosts IFN-gamma production. Our results showed a slight increase in IL-10 expression in the endometrium of some fertile women, although no significant differences were found in IFN-gamma and IL-5 expression. In contrast, analysis of IFN-gamma production by polyclonal activated lymphocytes from endometrium and/or peripheral blood from fertile women showed a significant increase compared to RSM. Analysis of SLAM protein expression in luteal phase endometrial samples showed a significant increase in the levels of the receptor in RSM women compared to fertile women. These results correlated with a significant augmentation of SLAM levels in peripheral blood T-lymphocytes from RSM patients. Interestingly, after treatment of RSM patients with paternal mononuclear cells, surface-SLAM-expression in T-cells from RSM patients significantly decreased up to levels comparable to those of fertile women. Taken together, our results suggest that endometrial cells have not a defined pattern-cytokine-production under pre-implatatory conditions, and SLAM might be a potential marker for the diagnosis of RSM and an indicator useful to follow up the patient response to allogeneic immunotherapy.

Modulation of CD44 in acute lymphoblastic leukemia identifies functional and phenotypic differences of human B cell precursors.

CD44 expression and other B cell markers were analyzed in 38 samples of B cell precursors (BCP) from patients with acute lymphoblastic leukemia (ALL). According to the expression of CD10 and CD44, we established the following five stages of BCP-ALL phenotypes that may represent different forms of interaction between BCP-ALL and bone marrow-adherent cells: stage 1, CD19+, CD44bright, CD10-; stage 2, CD19+, CD44bright, CD10dim/bright; stage 3, CD19+, CD44dim, CD10bright, CD20-/+; stage 4, CD19+, CD44dim, CD10dim, CD20+; and stage 5, CD19+, CD44bright, CD10-, CD20+. Next, we analyzed the modulation of CD44 according to the expression of the different BCP-ALL phenotypes by incubating the samples under different culture conditions, including addition of stromal cells and interleukin (IL)-7. In culture, the samples in stages 1 and 2 maintained high expression of CD44 and re-expressed this molecule when cultured after trypsin treatment, indicating ongoing synthesis of CD44. Similarly, the stage 3 samples cultured in the presence of stromal cells, IL-7, or both also upregulated CD44 expression in culture. In contrast, the low expression of CD44 on the presumably more mature stage 4 samples was not modified by the addition of stromal cells or IL-7 or when cultured after trypsin treatment, suggesting that those cells had arrested CD44 synthesis. We concluded that down-modulation of CD44 occurred in association with differentiation to phenotype stages 3 and 4 and we hypothesized that this down-modulation might be associated with the exit of BCP-ALL from the bone marrow.