Systemic lupus erythematosus (SLE) and Sj?gren?s syndrome (SS) are both heterogeneous autoimmune diseases with strong B cell aspects. A proportion of SLE and SS patients exhibit elevated serum BAFF (B cell activating factor of the TNF family); BAFF plays a key role in B cell homeostasis, survival and tolerance. BAFF transgenic (Tg) mice develop nephritis and salivary gland destruction that resemble aspects of SLE and SS respectively. Autoimmune disease development in BAFF Tg mice correlates with marginal zone (MZ) B cell expansion and the abnormal presence of MZ-like B cells outside of the spleen. The role of MZ B cells in BAFF induced autoimmune disease was analysed by crossing BAFF Tg mice with Lymphotoxin-β knockout mice (creating LTβ-BTg mice) which lack most peripheral lymph nodes, and also lack MZ B cells as a result of disrupted splenic architecture. LTβ-BTg mice were not protected against nephritis but exhibited reduced salivary gland infiltration and destruction. Indicating that the development of sialadenitis but not nephritis in BAFF Tg mice is MZ B cell dependent. Nephritis development in LTβ-BTg mice was associated with the detection of B-1 B cells in the inflamed kidneys. As B-1a B cell survival is dependent on the spleen, the contribution of B-1a B cells to nephritis development in BAFF Tg mice was assessed by crossing BAFF Tg mice to congenitally asplenic Hox11-/- mice (creating Hox11 -BTg mice). The absence of a spleen and B-1a B cells in Hox11-BTg mice delayed the nephritis development. In contrast, splenectomy of BAFF Tg mice at 12 weeks of age did not alter nephritis onset. In these mice B-1a B cells persisted in the peritoneal cavity and MZ-like B cells were detected in the periphery 8 months after surgery. In summary, nephritis development in BAFF Tg mice is unaltered by the absence of MZ B cells, but delayed in the absence of a spleen, MZ and B-1a B cells. Thus, B-1a and B-1b B cells may be potential targets for the treatment of nephritis in SLE patients with elevated BAFF.

Systemic lupus erythematosus (SLE) and Sj?gren?s syndrome (SS) are both heterogeneous autoimmune diseases with strong B cell aspects. A proportion of SLE and SS patients exhibit elevated serum BAFF (B cell activating factor of the TNF family); BAFF plays a key role in B cell homeostasis, survival and tolerance. BAFF transgenic (Tg) mice develop nephritis and salivary gland destruction that resemble aspects of SLE and SS respectively. Autoimmune disease development in BAFF Tg mice correlates with marginal zone (MZ) B cell expansion and the abnormal presence of MZ-like B cells outside of the spleen. The role of MZ B cells in BAFF induced autoimmune disease was analysed by crossing BAFF Tg mice with Lymphotoxin-β knockout mice (creating LTβ-BTg mice) which lack most peripheral lymph nodes, and also lack MZ B cells as a result of disrupted splenic architecture. LTβ-BTg mice were not protected against nephritis but exhibited reduced salivary gland infiltration and destruction. Indicating that the development of sialadenitis but not nephritis in BAFF Tg mice is MZ B cell dependent. Nephritis development in LTβ-BTg mice was associated with the detection of B-1 B cells in the inflamed kidneys. As B-1a B cell survival is dependent on the spleen, the contribution of B-1a B cells to nephritis development in BAFF Tg mice was assessed by crossing BAFF Tg mice to congenitally asplenic Hox11-/- mice (creating Hox11 -BTg mice). The absence of a spleen and B-1a B cells in Hox11-BTg mice delayed the nephritis development. In contrast, splenectomy of BAFF Tg mice at 12 weeks of age did not alter nephritis onset. In these mice B-1a B cells persisted in the peritoneal cavity and MZ-like B cells were detected in the periphery 8 months after surgery. In summary, nephritis development in BAFF Tg mice is unaltered by the absence of MZ B cells, but delayed in the absence of a spleen, MZ and B-1a B cells. Thus, B-1a and B-1b B cells may be potential targets for the treatment of nephritis in SLE patients with elevated BAFF.

L’infection au VIH a plusieurs effets délétères, dont la dérégulation du compartiment des lymphocytes B. Cette dérégulation s’installe rapidement après l’infection et perdure au-delà de la thérapie antirétrovirale, pouvant mener à diverses maladies auto-immunes ainsi qu’à des lymphomes. Chez les individus atteints du VIH, cette dérégulation mène à l’augmentation de la fréquence des cellules B précurseurs de la zone marginale (MZ) dans le sang ainsi qu’à leur production d’IL-10, à l’augmentation du B-cell activating factor (BAFF), et à l’hyperglobulinémie. De plus, Nef a été détecté dans le sérum et dans les cellules dendritiques des patients infectés, les niveaux de Nef des patients corrélant avec leurs niveaux de BAFF. L’analyse d’un RNAseq effectué sur des cellules B MZ précurseurs démontre la diminution hautement significative d’expression des NR4As et de CD83 chez les patients VIH+ progresseurs comparativement aux contrôles VIH- et aux élites contrôleurs. Notre équipe a d’ailleurs démontré le potentiel et la fonction Breg associés à l’expression des NR4As et CD83 chez les cellules B MZ précurseurs du sang et d’amygdales. Aussi, la majorité de cette population co-exprime CD73 et CD39, molécules impliquées dans la synthèse de l’adénosine, cette dernière ayant un contrôle sur l’expression des NR4As. Nous voulions donc étudier l’effet de niveaux élevés de BAFF et de Nef sur la modulation de l’expression des NR4As, de CD83, CD73 et CD39 chez les cellules B MZ d'amygdales et l’effet de la déhydroergotamine (DHE) sur ce modèle, des études ayant déjà illustré sa modulation positive des NR4As. Nous étions aussi intéressés par la production d’IL-10 par ces cellules B MZ ainsi que l’effet de Nef sur son expression. Nous avons trouvé qu’après incubation avec BAFF et Nef, l’expression de NR4A1 et de CD83 était souvent plus basse qu’après une incubation avec BAFF seul qui semblait augmenter l’expression de ces dernières, ce qui concorde avec les résultats du RNAseq mentionné plus haut. Après une incubation avec Nef seul, l’expression des NR4As et de CD83 est similaire à l’expression mesurée après une incubation sans traitement, mais certains patients ont démontré une diminution légère de l’expression de ces molécules, chose normale puisque les échantillons contenaient tous des niveaux basaux de BAFF. De plus, nos résultats démontrent que le DHE augmente l’expression de NR4A1 et 3 après que leur expression ait été diminuée par Nef et son effet semble être plus important au niveau des cellules B MZ et MZ précurseurs. Ces résultats suggèrent l’utilité du DHE pour la diminution des niveaux inflammatoires chez les individus atteints du VIH, les NR4As ayant un rôle anti-inflammatoire par la diminution des fréquences de NFkB, molécule modulée positivement par Nef. Nous avons remarqué que les populations exprimant IL-10 co-expriment principalement CD10. L’effet de Nef n’a malheureusement pas été remarqué sur l’expression d’IL-10, d’autres études étant nécessaires avec nos populations d’amygdales. Bref, nos résultats suggèrent l’utilité d’agents thérapeutiques ciblant les NR4As en addition à la thérapie antirétrovirale, leur modulation chez les lymphocytes B MZ et MZ précurseurs pouvant être un aspect clé du contrôle des niveaux inflammatoires chez les individus atteints du VIH. / HIV infection is accompanied by many deleterious effects, including B cell dysfunction. This dysfunction begins rapidly after infection and persists throughout the course of infection, without being fully restored by antiretroviral therapy. These alterations can lead to lymphomas and a multitude of auto-immune diseases. In people living with HIV, B-cell deregulation leads to an increase in “precursor-like” marginal zone (MZ) B cell frequency and their secretion of IL-10, to an increase in B-cell activating factor (BAFF), and to hyperglobulinemia. In addition, Nef has been detected in the serum and dendritic cells of infected individuals, its levels correlating with BAFF levels in affected patients. The analysis of an RNA-seq performed on precursor-like MZ B cells indicated a highly significant drop in NR4A1-3 and CD83 levels in HIV+ progressors compared to HIV- controls and HIV+ elite controllers. In fact, our team has previously demonstrated regulatory “Breg” potential associated to NR4A and CD83 expression in blood and tonsil precursor-like MZ B cells. The majority of this population also co-expresses CD73 and CD39, molecules involved in adenosine synthesis, adenosine being a regulator of NR4A expression. Therefore, we wanted to study the effects of BAFF and Nef on the modulation of NR4A, CD83, CD73 and CD39 expression in tonsil MZ B cells as well as the effect of dihydroergotamine (DHE) on this model, studies having already shown its positive modulation on the NR4As. We were also interested in the effects of Nef on IL-10 production by MZ B cells. We found that after incubation with BAFF and Nef, NR4A1 and CD83 expression was often lower than after an incubation with BAFF only, which seemed to increase their expression. This corresponds with the results of the RNA-seq mentioned above. After incubation with Nef alone, NR4A and CD83 expression is similar to the expression levels found after incubation without treatment. Some patients did demonstrate a slight decrease in the expression of these molecules, a normal observation considering all samples contain a basal level of BAFF. In addition, our results demonstrate that DHE increases NR4A1 and NR4A3 levels after their expression is initially decreased iv by Nef, and its effect seems more significant in MZ and precursor-like MZ B cells. These results suggest the usefulness of DHE for the reduction of inflammatory levels in individuals living with HIV, the NR4As having an anti-inflammatory role by decreasing the frequency of NFkB, a molecule positively modulated by Nef. Furthermore, we noted the populations expressing IL-10 mainly co-express CD10. Unfortunately, Nef’s previously reported effect on IL-10 expression was not noticed, indicating the need for further studies using our tonsil samples. In conclusion, our results suggest the value of therapeutic agents targeting NR4As in addition to antiretroviral therapy, their modulation of MZ and precursor-like MZ B cells possibly being the key to controlling inflammatory levels in individuals living with HIV.