Disrupted B-lymphocyte development and survival in interleukin-2-deficient mice

NK cells enhance CAR-T cell antitumor efficacy by enhancing immune/tumor cells cluster formation and improving CAR-T cell fitness

BACKGROUND

Chimeric antigen receptor (CAR)-T cell immunotherapy has modified the concept of treatment in hematological malignancies. In comparison with pediatric patients, where responses are maintained over many years, older patients, such as those with non-Hodgkin's lymphoma (NHL) and multiple myeloma (MM), present lower persistence of CAR-T cells that might be due to decreased fitness of T cells acquired with aging. Moreover, cord blood derived-NK cells (CB-NKs) and CAR-NK cells derived from CB-NK can be used 'off-the-shelf' as immune cells with antitumor properties for the treatment of cancer patients. However, to date, clinical studies have only demonstrated the safety of these therapies but not optimal efficacy. To confront the shortcomings of each therapy, we devised a novel approach consisting of simultaneous (CAR-)NK cell and CAR-T cell administration. In this setting, NK cells demonstrate an important immunoregulation of T cells that could be exploited to enhance the efficacy of CAR-T cells.

METHODS

A combinatorial treatment based on either CAR-T and CAR-NK cells or CB-NK and CAR-T cells in two models of NHL and MM was performed. Antitumor efficacy was analyzed in vitro and in vivo, and parameters related to early activation, exhaustion and senescence of T cells were analyzed.

RESULTS

We show that CAR-NK cells derived from CB-NK are only effective at high doses (high E:T ratio) and that their activity rapidly decreases over time in comparison with CAR-T cells. In comparison and to exploit the potential of 'off-the-shelf' CB-NK, we demonstrate that a low number of CB-NK in the CAR-T cell product promotes an early activation of CAR-T cells and their migration to MM cells leading to enhanced anti-MM efficacy. Moreover, cytokines related to CRS development were not increased, and importantly, CB-NK enhanced the fitness of both CAR^pos and CAR^neg T cells, promoting lower levels of exhaustion and senescence.

CONCLUSION

This study demonstrates a relevant immunoregulatory role of CB-NK collaborating with CAR-T cells to enhance their antitumor activity. A novel and different approach to consider in CAR-T cell immunotherapy studies is presented here with the goal to enhance the efficacy of the treatment.

IL-2/α-IL-2 Complex Treatment Cannot Be Substituted for the Adoptive Transfer of Regulatory T cells to Promote Bone Marrow Engraftment

Cell therapy with recipient Tregs achieves engraftment of allogeneic bone marrow (BM) without the need for cytoreductive conditioning (i.e., without irradiation or cytotoxic drugs). Thereby mixed chimerism and transplantation tolerance are established in recipients conditioned solely with costimulation blockade and rapamycin. However, clinical translation would be substantially facilitated if Treg-stimulating pharmaceutical agents could be used instead of individualized cell therapy. Recently, it was shown that interleukin-2 (IL-2) complexed with a monoclonal antibody (mAb) (clone JES6-1A12) against IL-2 (IL-2 complexes) potently expands and activates Tregs in vivo. Therefore, we investigated whether IL-2 complexes can replace Treg therapy in a costimulation blockade-based and irradiation-free BM transplantation (BMT) model. Unexpectedly, the administration of IL-2 complexes at the time of BMT (instead of Tregs) failed to induce BM engraftment in non-irradiated recipients (0/6 with IL-2 complexes vs. 3/4 with Tregs, p<0.05). Adding IL-2 complexes to an otherwise effective regimen involving recipient irradiation (1Gy) but no Treg transfer indeed actively triggered donor BM rejection at higher doses (0/8 with IL-2 complexes vs. 9/11 without, p<0.01) and had no detectable effect at two lower doses (3/5 vs. 9/11, p>0.05). CD8 T cells and NK cells of IL-2 complex-treated naïve mice showed an enhanced proliferative response towards donor antigens in vitro despite the marked expansion of Tregs. However, IL-2 complexes also expanded conventional CD4 T cells, CD8 T cells, NK cells, NKT cells and notably even B cells, albeit to a lesser extent. Notably, IL-2 complex expanded Tregs featured less potent suppressive functions than in vitro activated Tregs in terms of T cell suppression in vitro and BM engraftment in vivo. In conclusion, these data suggest that IL-2 complexes are less effective than recipient Tregs in promoting BM engraftment and in contrast actually trigger BM rejection, as their effect is not sufficiently restricted to Tregs but rather extends to several other lymphocyte populations.

Update on primary sclerosing cholangitis genetics

PURPOSE OF REVIEW

The pathogenesis of primary sclerosing cholangitis (PSC) involves heritable factors. This review summarizes the recent genetic studies and discusses the implications of identified risk loci.

RECENT FINDINGS

A total of 16 PSC susceptibility loci have been identified in genome-wide association studies and related study designs. At least 33 additional loci are involved in what is increasingly acknowledged to represent a general pool of genetic risk loci for immune-mediated diseases. One important group of genes is part of well characterized immune pathways (e.g. interleukin 2 signaling), whereas for other loci the relationship to PSC pathophysiology is less evident. Importantly, the loci collectively account for only 7.3% of overall PSC liability, thus pointing to a large contribution from environmental factors to PSC development. The individual PSC risk genes cannot be interpreted within a simple cause-effect model used for monogenic traits, but need to be explored for their individual biological correlates, preferably in a disease context. To some extent, as exemplified for the human leukocyte antigen and FUT2 associations, genetic findings may guide the discovery of interacting and co-occuring environmental susceptibility factors.

SUMMARY

Multiple PSC susceptibility loci are now available for exploration in experimental model systems and patient-centered research.

IL-21 contributes to fatal inflammatory disease in the absence of Foxp3+ T regulatory cells

The cytokine IL-21 has been shown to influence immune responses through both costimulatory effects on effector T cells and opposing inhibitory effects on T regulatory cells (Tregs). To distinguish the effect of IL-21 on the immune system from that of its effect on Tregs, we analyzed the role of IL-21/IL-21R signaling in mice made genetically deficient in IL-2, which exhibit a deficit in IL-2-dependent Foxp3 regulatory T cells and suffer from a fatal multiorgan inflammatory disease. Our findings demonstrate that in the absence of IL-21/IL-21R signaling, Il2(-/-) mice retained a deficiency in Tregs yet exhibited a reduced and delayed inflammatory disease. The improved health of Il2(-/-)Il21r(-/-) mice was reflected in reduced pancreatitis and hemolytic anemia and this was associated with distinct changes in lymphocyte effector populations, including the reduced expansion of both T follicular helper cells and Th17 cells and a compensatory increase in IL-22 in the absence of IL-21R. IL-21/IL-21R interactions were also important for the expansion of effector and memory CD8(+) T cells, which were critical for the development of pancreatitis in Il2(-/-) mice. These findings demonstrate that IL-21 is a major target of immune system regulation.

Liver transplantation for severe hepatitis in patients with common variable immunodeficiency

CVID is a heterogeneous group of primary immunodeficiency diseases characterized by hypogammaglobulinemia, recurrent bacterial infections, and frequent autoimmune manifestations. The post-transplant course of liver transplant recipients with CVID is rarely described. We report two patients with CVID complicated by severe enteropathy who underwent living donor liver transplantation for liver failure because of severe hepatitis. The post-transplant course was complicated by recurrent acute rejection, leading to ductopenic rejection in one and recurrent hepatitis in the other. We reviewed the tissue samples histologically and immunohistochemically. Native livers showed submassive hepatocyte necrosis in one and cirrhotic liver with active hepatitis in the other, both with infiltration of CD8+ T cells accompanied by endothelialitis and bile duct damage; the intestine contained increased numbers of intraepithelial CD8+ T cells with apoptosis of epithelial cells. The liver allograft exhibited acute rejection, with prominent CD8+ T cells infiltrating the bile duct or endothelium. In the allograft following the diagnosis of post-transplant recurrent hepatitis, CD8+ T cells comprised the majority of infiltrating cells in portal areas spilling over into hepatic parenchyma. Our cases suggest that T cells contribute to the pathogenesis of CVID in native organs as well as allografts and may constitute evidence of T-cell deregulation in the pathogenesis of CVID.

IL-2-controlled expression of multiple T cell trafficking genes and Th2 cytokines in the regulatory T cell-deficient scurfy mice: implication to multiorgan inflammation and control of skin and lung inflammation

Scurfy (Sf) mice bear a mutation in the Foxp3 transcription factor, lack regulatory T cells (Treg), develop multiorgan inflammation, and die prematurely. The major target organs affected are skin, lungs, and liver. “Sf mice lacking the Il2 gene (Sf.Il2–/–), despite being devoid of Treg, did not develop skin and lung inflammation, but the inflammation in liver remained [corrected]. Genome-wide microarray analysis revealed hundreds of genes that were differentially regulated among Sf, Sf.Il2(-/-), and B6 CD4(+) T cells, but the most significant changes were those encoding receptors for trafficking/chemotaxis/retention and cytokines. Our study suggests that IL-2 controls the skin and lung inflammation in Sf mice in an apparent "organ-specific" manner through two novel mechanisms: by regulating the expression of genes encoding a variety of receptors for T cell trafficking/chemotaxis/retention and by regulating Th2 cell expansion and cytokine production. Thus, IL-2 is potentially a master regulator for multiorgan inflammation and an underlying etiological factor for various diseases associated with skin and lung inflammation.

Influence of interleukin-2 deficiency on the generation of autoimmune B cells

The production of auto-antibodies is one of the predominant characteristics of autoimmune disorders. Because IL-2 deficient mice develop autoimmunity, we asked how IL-2 deficiency might impair endogenous mechanisms of B cell tolerance. To this end, we mated BALB/c anti-dsDNA H chain knock-in mice, in which B cells producing anti-dsDNA antibodies are properly regulated, with IL-2 deficient mice and assessed the phenotype of their offspring. IL-2 deficient mice expressing the anti-dsDNA H chain knock-in allele developed anti-dsDNA antibodies of both IgM and IgG isotypes. Production of these antibodies occurred through the disruption of several mechanisms of endogenous tolerance, including deletion, maturational arrest, and follicular exclusion. In summary, our results suggest that IL-2 plays an important role in regulating B cell tolerance.

The role of Fas in the immune system biology of IL-2R alpha knockout mice: interplay among regulatory T cells, inflammation, hemopoiesis, and apoptosis

Introducing lpr mutation prevents early mortality associated with IL-2Ralpha knockout (KO) mice, prompting us to determine the role of Fas in the immune system biology of IL-2Ralpha KO mice. Consistent with a defect in CD4+CD25+ regulatory T (Treg) cell expression, spontaneous lymphocyte activation in lymphoid organs was observed in 6-wk-old mice. In 16- to 22-wk-old mice, infiltration of leukocytes was observed in bone marrow, colon, lung, pancreas, lacrimal gland, and salivary gland, but not in heart, thyroid, liver, stomach, small intestine, ovary, and kidney. In the lymphocytes-infiltrated bone marrow, B cell lymphopoiesis was blocked at pro-B to pre-B/immature B stage, culminating in an age-dependent B cell loss in the periphery. These phenotypes were also observed in IL-2Ralpha KO mice bearing the lpr mutation (DM mice), indicating Treg cell function and the phenotypes attributed directly to Treg cell abnormality are largely Fas-independent. However, anemia and body weight loss were partially prevented, tissue cell apoptosis was inhibited, and lifespan was improved in the DM mice, demonstrating Fas-dependent elements in these processes. Our age-dependent, lifelong analysis of IL-2Ralpha KO and DM mice supports a CD4+CD25+ Treg cell-based mechanism for the abnormal immune system biology observed in IL-2Ralpha KO mice and provides a global view of the interplays among Treg cells, multiorgan inflammation, hemopoiesis, and apoptosis.

Interleukin 2 plays a central role in Th2 differentiation

Differentiation of naïve CD4 T cells into T helper (Th) 2 cells requires signaling through the T cell receptor and an appropriate cytokine environment. IL-4 is critical for such Th2 differentiation. We show that IL-2 plays a central role in this process. The effect of IL-2 on Th2 generation does not depend on its cell growth or survival effects. Stat5a(-/-) cells show diminished differentiation to IL-4 production, and forced expression of a constitutively active form of Stat5a replaces the need for IL-2. In vivo IL-2 neutralization inhibits IL-4 production in two models. Studies of restriction enzyme accessibility and binding of Stat5 to chromatin indicate that IL-2 mediates its effect by stabilizing the accessibility of the Il4 gene. Thus, IL-2 plays a critical role in the polarization of naive CD4 T cells to the Th2 phenotype.