Tbet+CD11c+ B cells, also known as age-associated B cells (ABCs), are pivotal contributors to hum... more Tbet+CD11c+ B cells, also known as age-associated B cells (ABCs), are pivotal contributors to humoral immunity following infection and in autoimmunity, yet their in vivo generation is incompletely understood. We used a mouse model of systemic acute lymphocytic choriomeningitis virus infection to examine the developmental requirements of ABCs that emerged in the spleen and liver. IL-21 signaling through STAT3 was indispensable for ABC development. In contrast, IFN-γ signaling through STAT1 was required for B cell activation and proliferation. Mice that underwent splenectomy or were deficient in lymphotoxin α generated hepatic ABCs despite the lack of secondary lymphoid organ contributions, suggesting that the liver supported de novo generation of these cells separately from their development in lymphoid organs. Thus, IFN-γ and IL-21 signaling have distinct, stage-specific roles in ABC differentiation, while the tissue microenvironment provides additional cues necessary for their development.
Coordinated gene expression programs enable development and function of T cell subsets. Follicula... more Coordinated gene expression programs enable development and function of T cell subsets. Follicular helper T (Tfh) cells coordinate humoral immune responses by providing selective and instructive cues to germinal center B cells. Here, we show that AP-1–independent NFAT gene expression, a program associated with hyporesponsive T cell states like anergy or exhaustion, is also a distinguishing feature of Tfh cells. NFAT signaling in Tfh cells, maintained by NFAT2 autoamplification, is required for their survival. ICOS signaling upregulates Bcl6 and induces an AP-1–independent NFAT program in primary T cells. Using lupus-prone mice, we demonstrate that genetic disruption or pharmacologic inhibition of NFAT signaling specifically impacts Tfh cell maintenance and leads to amelioration of autoantibody production and renal injury. Our data provide important conceptual and therapeutic insights into the signaling mechanisms that regulate Tfh cell development and function.
Inbred mice have provided the majority of knowledge regarding the pathogenesis of lupus. Their ea... more Inbred mice have provided the majority of knowledge regarding the pathogenesis of lupus. Their ease of use relates predominately to their more accessible immune organs, greater genetic homogeneity, and more predictable disease manifestations compared to humans. Many mouse strains develop lupus-like symptoms and signs, but the best studied include BXSB/Mp, (NZB × NZW)F1 and its derivative NZM, (NZB × SWR)Fl, and the congenic strains MRL/Mp and MRL/Mplpr/lpr (MRL/lpr) (1). Many studies have used the latter strain, which lacks functional activity of the CD95 (Fas) apoptosis antigen (2,3), a significant regulator of activated T and B cells (4–8); hence, its designation MRL/Fas lpr . Consequently, extrapolations of conclusions to systemic lupus erythematosus (SLE) in general must bear in mind the CD95 phenotype of 1pr animals, which possess severe defects in T- and B-cell tolerance (9–14), and which accumulate large numbers of T cells unable to undergo Fas-induced cell death after activation. Nevertheless, such animals with known genetic alterations provide substantially increased insight into the lupus immune system by allowing an examination of disease manifestations in the setting of known immune deficiencies and/or transgenes. Indeed, the availability of efficient genetic modification provides yet another advantage to the study of lupus in the murine system. This chapter highlights several studies in genetically manipulated lupus-prone mice, with particular attention to implications for human disease pathogenesis (Tables 1-3).
Intrathymic selection generates a peripheral repertoire of CD4 ؉ T cells with receptors that reta... more Intrathymic selection generates a peripheral repertoire of CD4 ؉ T cells with receptors that retain low affinity for self-peptide MHC complexes. Despite self-recognition, T cells remain tolerant even in the setting of microbial challenge and resultant costimulatory signals. We demonstrate here a novel mechanism for tolerance maintenance under conditions of self-recognition and strong costimulation. TCR engagement in vivo with a low-avidity peptide, as a mimic of self, provided with poly(I:C) (dsRNA) led to division of naive T cells that was dependent upon costimulatory signals; however, the dividing cells rapidly underwent deletion. By contrast, the surviving cells that were activated as evidenced by up-regulation of CD69 did not become effectors upon restimulation with the same ligand and maintained an effective response against agonist peptide. We suggest TCR engagement with self-peptide MHC complexes promotes tolerance maintenance during pathogen challenge, while preserving efficient reactivity for subsequent encounter with foreign Ags.
Follicular helper T cells provide signals that promote B cell development, proliferation, and pro... more Follicular helper T cells provide signals that promote B cell development, proliferation, and production of affinity matured and appropriately isotype switched antibodies. In addition to their classical locations within B cell follicles and germinal centers therein, B cell helper T cells are also be found in extrafollicular spaces – either in secondary lymphoid or non-lymphoid tissues. Both follicular and extrafollicular T helper cells drive autoantibody-mediated autoimmunity. Interfering with B cell help provided by T cells can ameliorate autoimmune disease in animal models and human patients. The next frontier in Tfh cell biology will be identification of Tfh-cell specific pathogenic changes in autoimmunity and exploiting them for therapeutic purposes.
Antibodies to the Sm and RNP antigens are diagnostic hallmarks in patients with systemic lupus er... more Antibodies to the Sm and RNP antigens are diagnostic hallmarks in patients with systemic lupus erythematosus. Both antigens are located on the U1 snRNP (small nuclear ribonucleoprotein particle), a complex of a small RNA and associated proteins that carry the antigenic determinants. This particle also plays an essential role in messenger RNA processing within the cell nucleus. Newer diagnostic techniques are available for detection of anti-Sm and antiRNP antibodies (the latter are now more appropriately called anti-U1 RNP antibodies) and a great deal of information on the molecular biology of snRNPs is currently available.
The murine popliteal lymph node assay (PLNA) was examined as a preclinical assay with the potenti... more The murine popliteal lymph node assay (PLNA) was examined as a preclinical assay with the potential to identify low-molecular-weight compounds (LMWCs) that are likely to be associated with immune-mediated drug hypersensitivity reactions (IDHRs) in humans. We hypothesized that the contact sensitizer oxazolone (OX) would cause a strong PLN reaction in naive mice and that the PLN reaction would be attenuated in mice orally pretreated with OX due to the induction of oral tolerance. In naive mice, OX induced a strong PLN reaction and caused dose-dependent increases in PLN size, weight, cellularity, percentage of CD4(+) PLN T cells, and percentage of PLN B cells, with a concomitant decrease in the percentage of CD8(+) PLN T cells. Next, the PLNA was conducted in mice gavaged three times with either OX or vehicle alone (olive oil). Mice pretreated with OX had suppressed PLN reactions following the footpad injection of OX (decrease in PLN size, weight, and cellularity), which was associated with an increase in the percentage of PLN CD8(+)T cells. In contrast, oral pretreatment with OX had no observable effect on the PLN reaction induced following footpad injection of the irrelevant hapten dinitrochlorobenzene (DNCB). Adoptive transfer studies were conducted to examine the mechanism of PLN hyporesponsiveness. It was found that either (1) unfractionated splenocytes or (2) purified CD8(+) splenocytes, but not (3) purified CD4(+) splenocytes isolated from mice gavaged with OX adoptively transferred PLN suppression to naive BALB/c mice. Because OX is not a pharmaceutical, we also examined the NSAID diclofenac (DF) (Voltaren). Like OX, DF caused dose-dependent increases in PLN size, weight, and cellularity in naive mice. Furthermore, like OX, the diclofenac-induced PLN reaction was attenuated in mice that had been orally pretreated three times with DF. However, splenocytes from mice orally treated with DF were not able to adoptively transfer PLN hyporesponsiveness. Collectively, these observations demonstrate that both OX and DF are potent immunostimulators in the PLNA. As importantly, these results demonstrate that the immunostimulating potential of OX and DF in the PLNA is significantly decreased in mice orally exposed to the respective drug, possibly due to the presence of a cellular mechanism of oral tolerance. For OX, the mechanism appears to involve, in part, CD8(+) T cells, whereas the mechanism(s) associated with PLN hyporesponsiveness using DF remain to be defined.
The small nuclear ribonucleoprotein 70K (snRNP 70K; U1-70 kDa) is an integral part of the spliceo... more The small nuclear ribonucleoprotein 70K (snRNP 70K; U1-70 kDa) is an integral part of the spliceosome, a large RNA-protein complex catalyzing the removal of introns from nuclear pre-mRNA. snRNP is one of the best-studied essential subunits of snRNPs, is highly conserved and its inactivation was shown to result in complete inhibition of splicing. Applying subtractive hybridization, we found a sequence with 100% identity to snRNP absent in fetal Down syndrome (DS) brain. This observation made us determine snRNP-mRNA steady-state levels and protein levels in brains of adult patients with DS. snRNP-mRNA and protein levels of five individual brain regions of DS and controls each, were determined by blotting techniques. snRNP-mRNA steady state levels were significantly decreased in DS brain. Performing Western blots with monoclonal and human antibodies, snRNP protein levels were decreased in several regions of DS brain, although one monoclonal antibody did not reveal different snRNP-immunoreactivity. Although decreased snRNP-protein could be explained by decreased mRNA-steady state levels, another underlying mechanism might be suggested: snRNP is one of the death substrates rapidly cleaved during apoptosis by interleukin-1-beta-converting enzyme-like (ICE) proteases, which was well-documented by several groups. As apoptosis is unrequivocally taking place in DS brain leading to permanent cell loses, decreased snRNP-protein levels may therefore reflect decreased synthesis and increased apoptosis-related proteolytic cleavage.
We have characterized autoantibodies to nuclear and nucleolar antigens in 112 patients with diffu... more We have characterized autoantibodies to nuclear and nucleolar antigens in 112 patients with diffuse scleroderma, CREST syndrome (calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasias), scleroderma overlap syndromes, or primary Raynaud's phenomenon by indirect immunofluorescence and radiolabeled immunoprecipitation assays. We noted for the first time that anti-Th RNP antibodies represent a common antibody specificity in scleroderma (occurring in 13% of patients with scleroderma-like illnesses) and that anti-NOR 90 antibodies are quite rare in American patients (none found). In addition, we describe 3 new scleroderma-associated autoantibodies.
Tbet+CD11c+ B cells, also known as age-associated B cells (ABCs), are pivotal contributors to hum... more Tbet+CD11c+ B cells, also known as age-associated B cells (ABCs), are pivotal contributors to humoral immunity following infection and in autoimmunity, yet their in vivo generation is incompletely understood. We used a mouse model of systemic acute lymphocytic choriomeningitis virus infection to examine the developmental requirements of ABCs that emerged in the spleen and liver. IL-21 signaling through STAT3 was indispensable for ABC development. In contrast, IFN-γ signaling through STAT1 was required for B cell activation and proliferation. Mice that underwent splenectomy or were deficient in lymphotoxin α generated hepatic ABCs despite the lack of secondary lymphoid organ contributions, suggesting that the liver supported de novo generation of these cells separately from their development in lymphoid organs. Thus, IFN-γ and IL-21 signaling have distinct, stage-specific roles in ABC differentiation, while the tissue microenvironment provides additional cues necessary for their development.
Coordinated gene expression programs enable development and function of T cell subsets. Follicula... more Coordinated gene expression programs enable development and function of T cell subsets. Follicular helper T (Tfh) cells coordinate humoral immune responses by providing selective and instructive cues to germinal center B cells. Here, we show that AP-1–independent NFAT gene expression, a program associated with hyporesponsive T cell states like anergy or exhaustion, is also a distinguishing feature of Tfh cells. NFAT signaling in Tfh cells, maintained by NFAT2 autoamplification, is required for their survival. ICOS signaling upregulates Bcl6 and induces an AP-1–independent NFAT program in primary T cells. Using lupus-prone mice, we demonstrate that genetic disruption or pharmacologic inhibition of NFAT signaling specifically impacts Tfh cell maintenance and leads to amelioration of autoantibody production and renal injury. Our data provide important conceptual and therapeutic insights into the signaling mechanisms that regulate Tfh cell development and function.
Inbred mice have provided the majority of knowledge regarding the pathogenesis of lupus. Their ea... more Inbred mice have provided the majority of knowledge regarding the pathogenesis of lupus. Their ease of use relates predominately to their more accessible immune organs, greater genetic homogeneity, and more predictable disease manifestations compared to humans. Many mouse strains develop lupus-like symptoms and signs, but the best studied include BXSB/Mp, (NZB × NZW)F1 and its derivative NZM, (NZB × SWR)Fl, and the congenic strains MRL/Mp and MRL/Mplpr/lpr (MRL/lpr) (1). Many studies have used the latter strain, which lacks functional activity of the CD95 (Fas) apoptosis antigen (2,3), a significant regulator of activated T and B cells (4–8); hence, its designation MRL/Fas lpr . Consequently, extrapolations of conclusions to systemic lupus erythematosus (SLE) in general must bear in mind the CD95 phenotype of 1pr animals, which possess severe defects in T- and B-cell tolerance (9–14), and which accumulate large numbers of T cells unable to undergo Fas-induced cell death after activation. Nevertheless, such animals with known genetic alterations provide substantially increased insight into the lupus immune system by allowing an examination of disease manifestations in the setting of known immune deficiencies and/or transgenes. Indeed, the availability of efficient genetic modification provides yet another advantage to the study of lupus in the murine system. This chapter highlights several studies in genetically manipulated lupus-prone mice, with particular attention to implications for human disease pathogenesis (Tables 1-3).
Intrathymic selection generates a peripheral repertoire of CD4 ؉ T cells with receptors that reta... more Intrathymic selection generates a peripheral repertoire of CD4 ؉ T cells with receptors that retain low affinity for self-peptide MHC complexes. Despite self-recognition, T cells remain tolerant even in the setting of microbial challenge and resultant costimulatory signals. We demonstrate here a novel mechanism for tolerance maintenance under conditions of self-recognition and strong costimulation. TCR engagement in vivo with a low-avidity peptide, as a mimic of self, provided with poly(I:C) (dsRNA) led to division of naive T cells that was dependent upon costimulatory signals; however, the dividing cells rapidly underwent deletion. By contrast, the surviving cells that were activated as evidenced by up-regulation of CD69 did not become effectors upon restimulation with the same ligand and maintained an effective response against agonist peptide. We suggest TCR engagement with self-peptide MHC complexes promotes tolerance maintenance during pathogen challenge, while preserving efficient reactivity for subsequent encounter with foreign Ags.
Follicular helper T cells provide signals that promote B cell development, proliferation, and pro... more Follicular helper T cells provide signals that promote B cell development, proliferation, and production of affinity matured and appropriately isotype switched antibodies. In addition to their classical locations within B cell follicles and germinal centers therein, B cell helper T cells are also be found in extrafollicular spaces – either in secondary lymphoid or non-lymphoid tissues. Both follicular and extrafollicular T helper cells drive autoantibody-mediated autoimmunity. Interfering with B cell help provided by T cells can ameliorate autoimmune disease in animal models and human patients. The next frontier in Tfh cell biology will be identification of Tfh-cell specific pathogenic changes in autoimmunity and exploiting them for therapeutic purposes.
Antibodies to the Sm and RNP antigens are diagnostic hallmarks in patients with systemic lupus er... more Antibodies to the Sm and RNP antigens are diagnostic hallmarks in patients with systemic lupus erythematosus. Both antigens are located on the U1 snRNP (small nuclear ribonucleoprotein particle), a complex of a small RNA and associated proteins that carry the antigenic determinants. This particle also plays an essential role in messenger RNA processing within the cell nucleus. Newer diagnostic techniques are available for detection of anti-Sm and antiRNP antibodies (the latter are now more appropriately called anti-U1 RNP antibodies) and a great deal of information on the molecular biology of snRNPs is currently available.
The murine popliteal lymph node assay (PLNA) was examined as a preclinical assay with the potenti... more The murine popliteal lymph node assay (PLNA) was examined as a preclinical assay with the potential to identify low-molecular-weight compounds (LMWCs) that are likely to be associated with immune-mediated drug hypersensitivity reactions (IDHRs) in humans. We hypothesized that the contact sensitizer oxazolone (OX) would cause a strong PLN reaction in naive mice and that the PLN reaction would be attenuated in mice orally pretreated with OX due to the induction of oral tolerance. In naive mice, OX induced a strong PLN reaction and caused dose-dependent increases in PLN size, weight, cellularity, percentage of CD4(+) PLN T cells, and percentage of PLN B cells, with a concomitant decrease in the percentage of CD8(+) PLN T cells. Next, the PLNA was conducted in mice gavaged three times with either OX or vehicle alone (olive oil). Mice pretreated with OX had suppressed PLN reactions following the footpad injection of OX (decrease in PLN size, weight, and cellularity), which was associated with an increase in the percentage of PLN CD8(+)T cells. In contrast, oral pretreatment with OX had no observable effect on the PLN reaction induced following footpad injection of the irrelevant hapten dinitrochlorobenzene (DNCB). Adoptive transfer studies were conducted to examine the mechanism of PLN hyporesponsiveness. It was found that either (1) unfractionated splenocytes or (2) purified CD8(+) splenocytes, but not (3) purified CD4(+) splenocytes isolated from mice gavaged with OX adoptively transferred PLN suppression to naive BALB/c mice. Because OX is not a pharmaceutical, we also examined the NSAID diclofenac (DF) (Voltaren). Like OX, DF caused dose-dependent increases in PLN size, weight, and cellularity in naive mice. Furthermore, like OX, the diclofenac-induced PLN reaction was attenuated in mice that had been orally pretreated three times with DF. However, splenocytes from mice orally treated with DF were not able to adoptively transfer PLN hyporesponsiveness. Collectively, these observations demonstrate that both OX and DF are potent immunostimulators in the PLNA. As importantly, these results demonstrate that the immunostimulating potential of OX and DF in the PLNA is significantly decreased in mice orally exposed to the respective drug, possibly due to the presence of a cellular mechanism of oral tolerance. For OX, the mechanism appears to involve, in part, CD8(+) T cells, whereas the mechanism(s) associated with PLN hyporesponsiveness using DF remain to be defined.
The small nuclear ribonucleoprotein 70K (snRNP 70K; U1-70 kDa) is an integral part of the spliceo... more The small nuclear ribonucleoprotein 70K (snRNP 70K; U1-70 kDa) is an integral part of the spliceosome, a large RNA-protein complex catalyzing the removal of introns from nuclear pre-mRNA. snRNP is one of the best-studied essential subunits of snRNPs, is highly conserved and its inactivation was shown to result in complete inhibition of splicing. Applying subtractive hybridization, we found a sequence with 100% identity to snRNP absent in fetal Down syndrome (DS) brain. This observation made us determine snRNP-mRNA steady-state levels and protein levels in brains of adult patients with DS. snRNP-mRNA and protein levels of five individual brain regions of DS and controls each, were determined by blotting techniques. snRNP-mRNA steady state levels were significantly decreased in DS brain. Performing Western blots with monoclonal and human antibodies, snRNP protein levels were decreased in several regions of DS brain, although one monoclonal antibody did not reveal different snRNP-immunoreactivity. Although decreased snRNP-protein could be explained by decreased mRNA-steady state levels, another underlying mechanism might be suggested: snRNP is one of the death substrates rapidly cleaved during apoptosis by interleukin-1-beta-converting enzyme-like (ICE) proteases, which was well-documented by several groups. As apoptosis is unrequivocally taking place in DS brain leading to permanent cell loses, decreased snRNP-protein levels may therefore reflect decreased synthesis and increased apoptosis-related proteolytic cleavage.
We have characterized autoantibodies to nuclear and nucleolar antigens in 112 patients with diffu... more We have characterized autoantibodies to nuclear and nucleolar antigens in 112 patients with diffuse scleroderma, CREST syndrome (calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasias), scleroderma overlap syndromes, or primary Raynaud's phenomenon by indirect immunofluorescence and radiolabeled immunoprecipitation assays. We noted for the first time that anti-Th RNP antibodies represent a common antibody specificity in scleroderma (occurring in 13% of patients with scleroderma-like illnesses) and that anti-NOR 90 antibodies are quite rare in American patients (none found). In addition, we describe 3 new scleroderma-associated autoantibodies.
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Papers by Joseph Craft