Sialyl Lewis x (CD15s) identifies highly differentiated and most suppressive FOXP3high regulatory T cells in humans.

CD4(+) regulatory T (Treg) cells expressing CD25 and the transcription factor forkhead box P3 (FOXP3) are indispensable for immunological self-tolerance and homeostasis. FOXP3(+)CD25(+)CD4(+) T cells in humans, however, are heterogeneous in function and differentiation status, including suppressive or nonsuppressive cells as well as resting or activated Treg cells. We have searched for cell surface markers specific for suppression-competent Treg cells by using a panel of currently available monoclonal antibodies reactive with human T cells. We found that CD15s (sialyl Lewis x) was highly specific for activated, terminally differentiated, and most suppressive FOXP3(high) effector Treg (eTreg) cells and able to differentiate them in various clinical settings from nonsuppressive FOXP3(+) T cells secreting inflammatory cytokines. For example, CD15s(+)FOXP3(+) eTreg cells were increased in sarcoidosis, whereas it was nonsuppressive CD15s(-)FOXP3(+) T cells that were expanded in lupus flares. FOXP3(+) cells induced from conventional CD4(+) T cells by T-cell receptor stimulation hardly expressed CD15s. CD15s(+)CD4(+) T-cell depletion was sufficient to evoke and enhance in vitro immune responses against tumor or viral antigens. Collectively, we have identified CD15s as a biomarker instrumental in both phenotypic and functional analysis of FOXP3(+)CD4(+) T-cell subpopulations in health and disease. It allows specific targeting of eTreg cells, rather than whole FOXP3(+)CD4(+) T cells, in controlling immune responses.

Reconstitution of B cell function in murine models of immunodeficiency.

Murine models of immunodeficiency were used to evaluate strategies that might allow B cell engraftment in patients with X-linked agammaglobulinemia. Mice with defects in Btk or mu heavy chain were given 2.5 x 10(6) bone marrow cells from wild-type congenic donors. In the absence of any preparative regimen or immunosuppression, Btk-deficient mice on the CBA background developed normal concentrations of serum IgM and IgG3 by 12 weeks posttransplant. By contrast, mu heavy chain-deficient mice on the C57BL/6 background required some immunosuppression to achieve engraftment. Treatment of these mice with anti-T-cell antibodies 2 and 4 days prior to transplant resulted in normal concentrations of serum immunoglobulins by 6 weeks posttransplant. These pretreated mice had only 10% of the normal number of splenic B cells and they had no evidence of donor T cell engraftment. These results suggest that myelotoxic drugs may not be needed to achieve B cell engraftment in B-cell-deficient subjects.

Activation of PPAR gamma and delta by conjugated linoleic acid mediates protection from experimental inflammatory bowel disease.

BACKGROUND & AIMS: The molecular targets for the protective actions of conjugated linoleic acid (CLA) on experimental inflammatory bowel disease (IBD) are unknown. We used a loss-of-function approach to investigate whether CLA ameliorated colitis through a peroxisome proliferator-activated receptor gamma (PPAR gamma)-dependent mechanism. METHODS: The expression of PPAR gamma, delta, and their target genes in the colon of mice fed control or CLA-supplemented diets was assayed after a 7-day dextran sodium sulfate (DSS) challenge by quantitative real-time polymerase chain reaction (PCR). Additionally, nuclear factor-kappa B (NF-kappaB) p65 activation was quantified in the colon. To determine the involvement of PPAR gamma in the mechanism of action of CLA directly, specific deletions of PPAR gamma in the colon were performed in mice by using the Cre-lox recombination system. Colonic PPAR gamma null mice and wild-type littermates were fed either a CLA-supplemented or a control diet for 42 days and challenged with 2.5% DSS. The therapeutic efficacy of CLA also was examined by using the CD4 + CD45RB hi transfer colitis model. RESULTS: CLA induced PPAR gamma and delta, transcriptionally modulated PPAR gamma and delta-responsive gene clusters involved in lipid metabolism (uncoupling protein [UCP]1, UCP3, PPAR gamma coactivator 1alpha [PGC-1alpha], and CD36) and epithelial cell maturation (Gob-4 and Keratin 20). Additionally, CLA repressed tumor necrosis factor alpha (TNF-alpha) expression and NF-kappaB activation while inducing the immunoregulatory cytokine transforming growth factor beta 1 (TGF-beta 1 ). Clinically, CLA ameliorated DSS- and CD4 + -induced colitis. Loss of the PPAR gamma gene in the colon abrogated the beneficial effects of CLA in DSS colitis. CONCLUSIONS: Our studies provide molecular evidence in vivo, suggesting that CLA ameliorates colitis through a PPAR gamma-dependent mechanism.