Acquisition of suppressive function by activated human CD4+ CD25- T cells is associated with the expression of CTLA-4 not FoxP3.

The role of CTLA-4 in regulatory T cell (Treg) function is not well understood. We have examined the role of CTLA-4 and its relationship with the transcription factor FoxP3 using a model of Treg induction in human peripheral blood. Activation of human CD4(+)CD25(-) T cells resulted in the appearance of a de novo population of FoxP3-expressing cells within 48 h. These cells expressed high levels of CTLA-4 and cell sorting on expression of CTLA-4 strongly enriched for FoxP3(+)-expressing cells with suppressive function. Culture in IL-2 alone also generated cells with suppressive capacity that also correlated with the appearance of CTLA-4. To directly test the role of CTLA-4, we transfected resting human T cells with CTLA-4 and found that this method conferred suppression, similar to that of natural Tregs, even though these cells did not express FoxP3. Furthermore, transfection of FoxP3 did not induce CTLA-4 and these cells were not suppressive. By separating the expression of CTLA-4 and FoxP3, our data show that FoxP3 expression alone is insufficient to up-regulate CTLA-4; however, activation of CD4(+)CD25(-) T cells can induce both FoxP3 and CTLA-4 in a subpopulation of T cells that are capable of suppression. These data suggest that the acquisition of suppressive behavior by activated CD4(+)CD25(-) T cells requires the expression of CTLA-4, a feature that appears to be facilitated by, but is not dependent on, expression of FoxP3.

Integration of CD28 and CTLA-4 function results in differential responses of T cells to CD80 and CD86.

CD80 and CD86 have the capacity to either stimulate or inhibit T cell responses through their receptors CD28 and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4). Blockade of CD80 and CD86 in autoimmune disease settings has revealed distinct outcomes, yet the differential functions of CD80 and CD86 are still unclear. We have studied the ability of individual ligands to stimulate primary responses in human CD4(+) T cells. Our data reveal both quantitative and qualitative differences between the ligands. Both CD80 and CD86 demonstrated the capacity to costimulate T cell proliferation. However, CD80 committed a greater number of T cells to divide with faster kinetics, consistent with it being a superior ligand for CD28. Once cell division had been initiated, all T cells undergoing cell division expressed CTLA-4, irrespective of whether CD80 or CD86 costimulation was used. However, only in the presence of CD80 was evidence of CTLA-4 engagement and inhibitory function observed. Finally, differences between CD80 and CD86 costimulation extended to the T cell phenotype, in particular the levels of CD40 ligand expression.

Physical and biomechanical characteristics of rat cervical ripening are not consistent with increased collagenase activity.

OBJECTIVE: The cervix progressively softens during pregnancy to allow stretch without rupture in labor. Cervical softening is the product of complex modifications that include increased proteoglycan-to-collagen ratio, increased hyaluronic acid and water content, and breakdown of collagen by matrix metalloproteases. The relative contribution of collagen breakdown to cervical ripening is unclear. We sought to identify, discriminate, and quantify the physical characteristics of rat cervix during pregnancy, labor, and both before and after exposure to either prostaglandin (PGE(2)) or the collagenolytic enzyme matrix metalloprotease-1 (MMP-1). STUDY DESIGN: Cervices were collected from nonpregnant rats in diestrus (n=4) and pregnant rats on d10 (n=4), d16 (n=11), d20 (n=5), and d22 (term) nonlabor (NL: n=4) and d22 in term labor (TL: n=7). Cervices were also collected from a separate group in preterm labor induced by RU486 (PTL: n=10). The effect of PGE(2) on cervical characteristics was determined after intravaginal placement of PGE(2) gel (0.5 mg PGE(2): n=3) or placebo metylcellulose gel (CRL(PG) n=6) for 20 hours before euthanasia on d16. The effect of collagen was determined by incubating in vitro cervices from untreated d16 rats with (MMP-1: n=3) and without (CRL(MMP): n=7) activated collagenase before tensile testing. Tensile properties were quantitated by using Shimadzu EZ-test instrumentation (Shimadzu North America, Columbia, Md) with a stretching regimen that mimicked labor contractions while recording the force opposed by the tissue. Parameters such as the slope (a measure of stiffness), yield point (YP; moment the tissue changes its proprieties from elastic to plastic), and break point (BP; a measure of tissue strength) were recorded and analyzed. The plateau was defined as the phase after YP but before BP. RESULTS: Compared with d16, cervical extensibility increased significantly by d20 (slope d16: 0.41 +/- 0.03 N/mm vs d20: 0.19 +/- 0.05 N/mm, P < .01), and during both PTL (slope: 0.17 +/- 0.03 N/mm) and TL (slope: 0.11 +/- 0.02 N/mm). This increase was mimicked by PGE(2) (slope PGE(2): 0.24 +/- 0.03 vs CRL(PG): 0.40 +/- 0.05 N/mm, P=.04), but not by collagenase (slope MMP-1: 0.35 +/- 0.02 vs CRL(MMP): 0.38 +/- 0.05 N/mm, P>.05). YP was significantly reduced as pregnancy advanced, whereas BP increased, suggesting both increased plasticity (compliance) and strength. However, the plateau length increased 3-fold both by d20 and after PGE(2). In contrast, the addition of MMP-1 reduced the plateau. BP occurred significantly earlier in collagenase-treated tissues, but later in PTL-, TL-, and PGE(2)-treated cervices. CONCLUSION: The changes in physical properties of the rat cervix during physiologic ripening are similar to those induced by PGE(2) and RU486, and consist of increased extensibility, compliance, and strength. These changes cannot be attributed to increased collagenase activity, which would decrease tissue compliance and strength.