Impaired regulatory T cell function in germ‐free mice

Abstract

Regulatory T cells (Treg) are crucial for the maintenance of tolerance to auto-antigens and harmless exogenous antigens. Here, we studied the role of the commensal microbiota for the development and function of Treg. CD4 + CD25 + T cells were obtained from peripheral lymph nodes (PLN) and mesenteric lymph nodes (MLN) of germ-free (GF) and conventional (conv) NMRI mice and tested for phenotype and functional suppressive capacity. CD4 + CD25 + T cells from GF mice showed a lower relative gene expression of fork head box p3 gene (Foxp3) and were not as potent suppressors in vitro as CD4 + CD25 + T cells from conv animals. Intracellular staining for Foxp3 and CTLA-4 revealed proportional and regional differences in putative Treg subsets between conv and GF mice. Fewer of the CD4 + CD25 + T cells in GF MLN expressed Foxp3 and CTLA-4, while the expression of these markers was similar amongst the CD4 + CD25 + T cells in PLN of conv and GF mice. The largest difference between conv and GF Treg was observed in the liver draining celiac lymph node, where GF mice had fewer putative Treg as compared to conv mice. We propose that the presence of a microbial flora favors the development of a fully functional Treg population. IntroductionRegulatory T cells down-regulate unwanted and exaggerated immune reactions to auto-antigens as well as innocuous environmental antigens. Different subsets of Treg have been defined. Natural CD4 + CD25 + Treg are positively selected for tissue-specific self-Ag in the thymus and exert their suppressive effect by cell-cell contact-dependent mechanisms [1]. Deficiency in the Treg population or neonatal thymectomy result in multiorgan autoimmune diseases [2][3][4][5][6][7][8]. Treg are characterized by a dense surface expression of CD25 (the a-chain of the IL-2-receptor), glucocorticoidinduced TNF receptor (GITR) and intracellular CTLA-4, however, these markers may be present on activated T cells. CD4 + CD25 + Tregs appear to be unique in transcribing the fork head box p3 gene (Foxp3) transcription factor [6,9], which enable their identification either with PCR are or newly developed mAb to the Foxp3 protein. Lack of a functional Foxp3 gene result in the severe autoimmune syndrome IPEX (immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome), characterized by organ-specific autoimmunity, colitis and high IgE levels [10,11]. Mice with spontaneous or induced mutations in the Foxp3 gene that impair Foxp3 expression fail to develop CD4 + CD25 + Treg and exhibit a syndrome similar to IPEX [5,6].Other subsets of Treg are induced in the periphery and are referred to as Th3 [12][13][14] and Tr1 cells [15][16][17][18][19] can also generate Treg. This implies that the state of the APC and the local cytokine milieu, e.g. in the normal gut where both IL-10 and TGF-b are abundant, can determine the outcome of an immune reaction, and that Treg are induced under these circumstances.The aim of this study was to investigate the phenotype and functionality of CD4 + CD25 + Treg from germ-free (GF) ...

Dynamic Development of Homing Receptor Expression and Memory Cell Differentiation of Infant CD4+CD25high Regulatory T Cells

“…The fetal intestine is sterile at birth, but colonization by a variety of microorganisms begins directly after delivery (31). Because murine studies show that exposure to bacterial Ags favor the generation and/or expansion of functional Treg it is likely that acquisition of commensal flora is necessary to kick-start the tolerogenic mechanisms in of the immune system (32)(33)(34). In addition, Treg from germfree mice are less suppressive than those from conventional or colonized but pathogen-free mice, and they also express less FOXP3 than conventional mice (33,34).…”

Neonatal exposure to staphylococcal superantigen improves induction of oral tolerance in a mouse model of airway allergy

“…Natural thymic-dependent Treg (CD4 1 CD25 hi FoxP3 1 ) are fundamental in protection against autoimmunity, gut inflammation and IgE responses. This cell subset has reduced functional capacity in germ-free animals [8].…”

“…Natural thymic-dependent Treg (CD4 1 CD25 hi FoxP3 1 ) are fundamental in protection against autoimmunity, gut inflammation and IgE responses. This cell subset has reduced functional capacity in germ-free animals [8].The strongest T-cell activators known are the ''superantigens'', exotoxins produced by certain pathogenic bacteria such as Staphylococcus aureus. These include staphylococcal enterotoxin A, B, C, D and E, as well as toxic shock syndrome toxin-1.…”

Permissive/Protective Interplay of Microbiota with T Cell Adaptive Immune Response in Colon Cancer

“…It has been previously shown that the number of T cells remarkably decreases in germ-free mice (mice without intestinal microbiota), suggesting that T cells accumulate following recruitment by bacterial materials (23)(24)(25). The specificity of these cells is not known at present, although it seems that many of them are probably exclusive to commensal microbiota and the products to prevent damage caused by pathogens or toxins (22).…”