SNAPSHOT

AOP ID and Title:

---

Short Title: Immune dysfunction induced by JAK3 inhibition

Authors

---

Yasuhiro Yoshida (1) Takao Ashikaga (1) Tomoki Fukuyama (1) Ken Goto (1) Shinko Hata (1) Shigeru Hisada (1) Shiho Ito (1) Hiroyuki Komatsu (1) Sumie Konishi (1) Tadashi Kosaka (1) Kiyoshi Kushima (1) Shogo Matsumura (1) Takumi Ohishi (1) Yasuharu Otsubo (1) Junichiro Sugimoto (1)

(1) AOP Working Group, Testing Methodology Committee, The Japanese Society of Immunotoxicology

Corresponding author: Yasuhiro Yoshida (freude@med.uoeh-u.ac.jp)

Status

Abstract

---

Signal transduction between immune-related cells depends in many cases on cytokines and takes place via cell surface cytokine receptors as well as direct cell-to-cell interaction. Cytokines influence the movement, proliferation, differentiation, and activation of lymphocytes and other leukocytes in a variety of ways.

Some receptors for cytokines require and activation step through a Janus-kinase (JAK) Signal Transducers and Activator of Transcription (STAT) system. When cytokine binds to its specific cytokine receptors, the cytokine receptors form dimers, which more closely resemble the JAK molecules. The JAK then activates to phosphorylate adjacent cytokine receptors. STATs bind to the phosphorylated sites of the receptors and are then phosphorylated by the activated JAK. The phosphorylated STAT is dimerized  to be translocated into nucleus and bind to promoter regions of cytokine genes, which starts transcription of cytokine genes in the nucleus.

In mammals, four JAK families of enzymes (JAK1, JAK2, JAK3, TYK2) and seven STATs (STAT1, STAT2, STAT3, STAT4, STAT5a, STAT5b, STAT6) are utilized by more than 50 cytokines and growth factors to mediate intracellular signaling. In particular, pro-inflammatory cytokines such as interferon-γ (IFN-γ), interleukin-2 (IL-2), IL-4, IL-6, IL-13, IL-21 and IL-23 have been implicated in inflammatory diseases that utilize the JAK pathway. In addition, TH2 derived cytokines, including IL-31 and thymic stromal lymphopoietin (TSLP), are ligands for murine and human sensory nerves and have a critical function that evokes itchiness. Because these cytokines also interact with JAK, several JAK-inhibitors have received a lot of attention recently as a therapeutic agent for major inflammatory diseases and pruritic diseases. However, immunotoxic events due to inhibition of the JAK pathway have yet to be examined.

This AOP focuses on the inhibition of JAK3, which is required for signal transduction by cytokines through the common gamma (γ) chain of the interleukin receptors for IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21. This AOP proposes JAK3 inhibition as an MIE that leads to suppression of T cell-dependent antibody response (TDAR) as an AO. TDAR is frequently affected under immunosuppressive conditions and is a major endpoint in many preclinical immunotoxicity studies. In this proposed AOP, JAK3 selective inhibitors (e.g. PF-06651600, RB1) are stressors, blockade of STAT5 phosphorylation is KE1, suppression of STAT5 binding to the promoter regions of cytokine genes is KE2, and subsequent suppression of IL-2 production is KE3.

Background

---

Although there are numerous stressors that inhibit JAK3 activity, this AOP is based on immunosuppression caused by recently developed, highly selective JAK3 inhibitors PF-06651600 and RB1, about which a significant body of scientific literature has been published.

We look forward to future amendments to this AOP with up-to-date information on other stressors, which will clarify the link between inhibition of JAK activity and impairment of TDAR.

Summary of the AOP

Events

Molecular Initiating Events (MIE), Key Events (KE), Adverse Outcomes (AO)

Key Event Relationships

Overall Assessment of the AOP

Janus kinases (JAKs) are a family of nonreceptor tyrosine kinase and consists of four members: JAK1, JAK2, JAK3, and Tyk2 (1). All four members mediate signals initiated by cytokines through interactions with receptors for IL-2, IL-5, IL-7, IL-9, and IL-15 via the common γ chain (2). Previous studies with IL-2Rγ-null mice showed that JAK3 is related to the development of spontaneous IBD symptoms (3). Moreover, abnormal activation of JAK3 was associated with human hematological (4), indicating that a tight balance of its activity was essential for normal hematopoietic development.Janus kinases (JAKs) are a family of nonreceptor tyrosine kinase and consists of four members: JAK1, JAK2, JAK3, and Tyk2 (1). Different studies have shown that JAK3 is widely expressed in different organs (2). Previous studies with IL-2Rγ-null mice showed that JAK3 is related to the development of spontaneous IBD symptoms (3). Moreover, abnormal activation of JAK3 was associated with human hematological (4), indicating that a tight balance of its activity was essential for normal hematopoietic development.

Although JAK1, JAK2, and Tyk2 are each widely expressed, JAK3 is predominantly expressed in hematopoietic cells and is known to associate only with the common γ (γc) chain of the interleukin-2 (IL-2), IL-4, IL-7, IL-9, and IL-15 receptors (5). Homozygous  mutant mice in which the JAK3 gene had been disrupted were generated by gene targeting. JAK3-deficient mice had profound reductions in thymocytes and severe B cell and T cell lymphopenia similar to severe combined immunodeficiency disease (SCID), and the residual T cells and B cells were functionally deficient. Thus, JAK3 plays a critical role in γc signaling and lymphoid development.

---

Domain of Applicability

Life Stage Applicability Taxonomic Applicability Sex Applicability

This proposed AOP involves inhibition of JAK activity leading to suppression of TDAR and is not dependent on life stage, sex, or age. Since JAK3 inhibitors (PF-06651600, RB1) are currently under a phase 2 clinical evaluation to treat rheumatoid arthritis, the AOP appears to be applicable to all life stages. Since JAK3 inhibitor-induced outcomes in humans are mimicked by similar responses in a variety of animal models, including non-human primates and rodents, immunosuppression induced by inhibition of JAK3 activity is considered to occur across a variety of mammalian species.

Essentiality of the Key Events

MIE and later events: JAK3-knockout (KO) mice

JAK3 was initially identified (1,2) in studies to identify the JAK family member that was involved in the signaling of a group of cytokines that shared in common the utilization of the γc chain first identified in the interleukin 2 (IL-2) receptor complex. It was subsequently demonstrated that JAK3 physically associates with the γc chain and is activated in a receptor complex that also contains JAK1, which associates with the ligand specific alpha or beta chain of the receptors (3). JAK3 is somewhat unique within the JAK family in that it is predominantly expressed in hematopoietic cells and is only activated in the responses to cytokines that use the γc chain (4). The phenotype of the JAK3 deletion mice was quite striking and consisted of a range of deficiencies which collectively constituted SCID (5,6). At the same time, two groups identified individuals that lacked JAK3 and exhibited somatically acquired SCID (7,8). One of the most striking components of the phenotype is the dramatic reduction seen in both the T and B cell lineages. Comparable reductions are seen in mice that lack IL-7 (9), the IL-7 receptor alpha chain (10), or the γc chain. In spite of the reduced numbers, the cells that do develop are phenotypically normal. These results are consistent with the hypothesis that activation of JAK3 give it a critical role in the expansion but not the differentiation of early lymphoid lineage-committed cells. In addition to the reduced numbers, the differentiated lymphoid cells that are generated fail to respond to the spectrum of cytokines that utilize the γc chain and activate JAK3 normally.

Stressor: B6.Cg-Nr1d1tm1Ven/LazJ mouse

The B6.Cg-Nr1d1tm1Ven/LazJ mouse line harbors a spontaneous mutation in JAK3, which generates an SCID phenotype with an inability to generate antigen-independent professional cytokine-producing innate lymphoid cells (ILCs). Mechanistically, JAK3 deficiency blocks ILC differentiation in the bone marrow at the ILC progenitor (ILCP) and the pre-NK cell progenitor (pre-NKP). Similar phenomenon was further demonstrated by the pan-JAK inhibitor tofacitinib and specific JAK3 inhibitor PF-06651600. Both JAK-inhibitors impair the ability of human intraepithelial ILC1 (iILC1) to produce IFN-γ, without affecting ILC3 production of IL-22. Both inhibitors impaired the proliferation of iILC1 and ILC3 and differentiation of human ILC in vitro. These findings indicate that JAK3 deficiency blocks innate lymphoid cell development (11).

KE1 and later events: STAT5-KO mice

STAT5 plays a major role in regulating vital cellular functions such as proliferation, differentiation, and apoptosis of hematopoietic and immune cells (12,13). STAT5 is activated by phosphorylation of a single tyrosine residue (Y694 in STAT5) and negatively regulated by dephosphorylation. A wide variety of growth factors and cytokines can activate STAT5 through the JAK-STAT pathway. The activation of STAT5 is transient and tightly regulated in normal cells (14).

The following phenotypes are observed in STAT5-KO mice:

The transcription factor STAT5 is expressed in all lymphocytes and plays a key role in multiple aspects of lymphocyte development and function (15). STAT5 was initially identified as a transcription factor activated by prolactin in mammary gland epithelial cells (16,17). Subsequent studies identified STAT5 binding activity in T cells (18), and it was later established that STAT5 was expressed in multiple cell types and activated by a number of cytokines, including the common gamma chain (γc)-dependent cytokines interleukin 2 (IL2), IL4, IL7, IL13, and IL15 (19).

 

STAT5 in T-cell development

The observation that STAT5 is activated by multiple cytokines in T cells suggested that it might play a critical role in the development or function (or both) of these cells. Disruption of Stat5a or Stat5b genes alone resulted in relatively modest phenotypes; for example, Stat5a-/- mice had defects in mammary gland development and lactation while Stat5b-/- mice had defects in response to growth hormone in male mice and natural killer cell proliferation (20,21). To determine whether combined deletion of Stat5a and Stat5b might result in more profound immunodeficiencies, subsequent studies deleted the first coding exons of both Stat5a and Stat5b. This intervention resulted in the production of truncated forms of STAT5a and STAT5b that acted as functional hypomorphs. These mice too had surprisingly mild defects in lymphocyte development, although T cells were grossly dysfunctional, as they could no longer proliferate in response to IL2 (22,23). Finally, complete deletion of Stat5a and Stat5b using Cre-LoxP approaches demonstrated that STAT5a and STAT5b are absolutely required for lymphocyte development, as Stat5a/b-/- mice had profound blocks in lymphocyte development, which mimicked that observed in Il7r-/- mice (24,25). These studies definitively demonstrated that the STAT5 hypomorph mice retained significant STAT5 function.

Weight of Evidence Summary

Biological Plausibility

T-cell development is mainly regulated by JAK-STAT system, and JAK3 deficiency in T cells is known to induce multiple types of immunosuppression, including T cell-dependent antibody response (TDAR).

JAK3-deficient mice had profound reductions in thymocytes and severe B cell and T cell lymphopenia similar to SCID disease, and the residual T cells and B cells were functionally deficient (10).

Mice lacking JAK3 also showed a severe block in B cell development at the pre-B stage in the bone marrow. In contrast, although the thymuses of these mice were small, T cell maturation progressed relatively normally. In response to mitogenic signals, peripheral T cells in JAK3-deficient mice did not proliferate and secreted small amounts of IL-2. These data demonstrate that JAK3 is critical for the progression of B cell development in the bone marrow and for the functional competence of mature T cells (5).

Furthermore, the abnormal architecture of lymphoid organs suggested the involvement of JAK3 in the function of epithelial cells. T cells developed in the mutant mice did not respond to either IL-2, IL-4, or IL-7 (26).

Specific JAK3 inhibitor PF-06651600 or RB1, which selectively inhibited JAK3 with an over 100-fold preference over JAK2, JAK1, and TYK2 in the kinase assay, displayed reduced inflammation and associated pathology in collagen-induced-arthritis mice. Importantly, with PF-06651600 or RB1 administration, pro-inflammatory cytokines and JAK3 and STATs phosphorylation decreased in mice, suggesting that the inhibition of JAK3/STAT signaling was closely correlated with induction of multiple types of immunosuppression, including TDAR .

Quantitative Consideration

KER1 (MIE=>KE 1)：

Interleukin 2 (IL-2) activated STAT5 via distinct pathways (30).

IL-2 have been demonstrated to stimulate STAT5 and induce tyrosine phosphorylation of STAT5. Treatment of highly selective JAK3 inhibitors (PF-06651600 or RB1) treatment clearly suppresses the complex formation of STAT5 in the nucleus.

Highly-selective JAK3 inhibitor RB1 inhibited the phosphorylation of STAT5 elicited by IL-2 at IC50 value of 31 nM in the raw peripheral blood mononuclear cells (PBMCs) of humans. PBMCs were isolated from the buffy coats of healthy volunteers using density gradient centrifugation on Lymphoprep. Cells were cultured in complete RPMI 1640 medium (containing 10% foetal bovine serum, 100 mg/ml streptomycin and 100 U/ml penicillin) plus 10 μg/ml lectin phytohemagglutinin (PHA) for 3 days and then treated with either recombinant human IL-6 (400 ng/ml), recombinant human IL-2 (100 ng/ml), or recombinant human GM-CSF (50 ng/ml) at 37 °C for 20 min. To terminate the stimulation, cells were fixed with Lyse/Fix Buffer and then incubated with 100% methanol for 30 minutes; cells were incubated with anti-pSTAT3 and anti-CD4 Abs, or anti-pSTAT5 and anti-CD4 Abs at 4 °C overnight, washed twice with PBS, and analysed with an flow cytometer (31).

Fluorescence intensity for phospho-STAT5 in CD3-positive lymphocytes increased upon incubation of peripheral blood with IL-2. Peficitinib inhibited STAT5 phosphorylation in a concentration-dependent manner with a mean IC50 of 124 nM (101 and 147 nM for two rats). Additionally, the effect of peficitinib on IL-2 stimulated STAT5 phosphorylation in human peripheral T-cells was evaluated. Paralleling results in rats, the fluorescence intensity of phospho-STAT5 in CD3-positive lymphocytes increased in human peripheral blood after adding IL-2, but peficitinib inhibited STAT5 phosphorylation in a concentration-dependent manner with a mean IC50 of 127 nM in human lymphocytes (26).

 

KER2 (KE1 =>KE 2)：

IL-2 activated STAT5 (30).

IL-2 have been demonstrated to stimulate STAT5 and induce tyrosine phosphorylation of STAT5. These IL-2-induced STATs have an identical DNA binding specificity and immunoreactivity.

 

KER3：(KE2 =>KE 3)：

IL-2 activated STAT5 (30) 

IL-2 have been demonstrated to stimulate STAT5 and induce tyrosine phosphorylation of STAT5. These IL-2-induced STATs have an identical DNA binding specificity and immunoreactivity.

Gel mobility shift assay showed that IL-2 activation induced STAT5 dimerization and DNA binding to gamma interferon-activated site (GAS) motif in IL-2 promoter region (32).

 

KER4：(KE3 =>AO)：

As for IL-2 and antibody production, in vitro T-cell-induced polyclonal B cell activation to produce antibody was inhibited with anti-IL-2 and anti-IL-2R antibodies (33). In addition, cynomolgus monkeys treated with CsA showed suppression of IL-2 and TDAR using sheep red blood cells with a dose dependent manner (34).

In the human T-B cell co-culture stimulated with anti-CD3 monoclonal antibody, CNIs of FK506 and CsA lowered the levels of T-cell cytokines including IL-2 and IL-4 and inhibited IgM and IgG productions with a dose-dependent manner (35).

These results show the quantitative relationships between the inhibition of IL-2 by specific antibodies or CNI and suppression of antibody production.

 

References

---

1. Johnston, J. A., Kawamura, M., Kirken, R. A., Chen, Y. Q., Blake, T. B., Shibuya, K., Ortaldo, J. R., McVicar, D. W., and O'Shea, J. J. (1994) Phosphorylation and activation of the Jak-3 Janus kinase in response to interleukin-2. Nature 370, 151-153
2. Witthuhn, B. A., Silvennoinen, O., Miura, O., Lai, K. S., Cwik, C., Liu, E. T., and Ihle, J. N. (1994) Involvement of the Jak-3 Janus kinase in signalling by interleukins 2 and 4 in lymphoid and myeloid cells. Nature 370, 153-157
3. Miyazaki, T., Kawahara, A., Fujii, H., Nakagawa, Y., Minami, Y., Liu, Z. J., Oishi, I., Silvennoinen, O., Witthuhn, B. A., Ihle, J. N., and et al. (1994) Functional activation of Jak1 and Jak3 by selective association with IL-2 receptor subunits. Science 266, 1045-1047
4. Ihle, J. N., Nosaka, T., Thierfelder, W., Quelle, F. W., and Shimoda, K. (1997) Jaks and Stats in cytokine signaling. Stem Cells 15 Suppl 1, 105-111; discussion 112
5. Nosaka, T., van Deursen, J. M., Tripp, R. A., Thierfelder, W. E., Witthuhn, B. A., McMickle, A. P., Doherty, P. C., Grosveld, G. C., and Ihle, J. N. (1995) Defective lymphoid development in mice lacking Jak3. Science 270, 800-802
6. Thomis, D. C., Gurniak, C. B., Tivol, E., Sharpe, A. H., and Berg, L. J. (1995) Defects in B lymphocyte maturation and T lymphocyte activation in mice lacking Jak3. Science 270, 794-797
7. Macchi, P., Villa, A., Giliani, S., Sacco, M. G., Frattini, A., Porta, F., Ugazio, A. G., Johnston, J. A., Candotti, F., O'Shea, J. J., and et al. (1995) Mutations of Jak-3 gene in patients with autosomal severe combined immune deficiency (SCID). Nature 377, 65-68
8. Russell, S. M., Tayebi, N., Nakajima, H., Riedy, M. C., Roberts, J. L., Aman, M. J., Migone, T. S., Noguchi, M., Markert, M. L., Buckley, R. H., O'Shea, J. J., and Leonard, W. J. (1995) Mutation of Jak3 in a patient with SCID: essential role of Jak3 in lymphoid development. Science 270, 797-800
9. von Freeden-Jeffry, U., Vieira, P., Lucian, L. A., McNeil, T., Burdach, S. E., and Murray, R. (1995) Lymphopenia in interleukin (IL)-7 gene-deleted mice identifies IL-7 as a nonredundant cytokine. J Exp Med 181, 1519-1526
10. Peschon, J. J., Morrissey, P. J., Grabstein, K. H., Ramsdell, F. J., Maraskovsky, E., Gliniak, B. C., Park, L. S., Ziegler, S. F., Williams, D. E., Ware, C. B., Meyer, J. D., and Davison, B. L. (1994) Early lymphocyte expansion is severely impaired in interleukin 7 receptor-deficient mice. J Exp Med 180, 1955-1960
11. Robinette, M. L., Cella, M., Telliez, J. B., Ulland, T. K., Barrow, A. D., Capuder, K., Gilfillan, S., Lin, L. L., Notarangelo, L. D., and Colonna, M. (2018) Jak3 deficiency blocks innate lymphoid cell development. Mucosal Immunol 11, 50-60
12. Rani, A., and Murphy, J. J. (2016) STAT5 in Cancer and Immunity. J Interferon Cytokine Res 36, 226-237
13. Wittig, I., and Groner, B. (2005) Signal transducer and activator of transcription 5 (STAT5), a crucial regulator of immune and cancer cells. Curr Drug Targets Immune Endocr Metabol Disord 5, 449-463
14. Quezada Urban, R., Diaz Velasquez, C. E., Gitler, R., Rojo Castillo, M. P., Sirota Toporek, M., Figueroa Morales, A., Moreno Garcia, O., Garcia Esquivel, L., Torres Mejia, G., Dean, M., Delgado Enciso, I., Ochoa Diaz Lopez, H., Rodriguez Leon, F., Jan, V., Garzon Barrientos, V. H., Ruiz Flores, P., Espino Silva, P. K., Haro Santa Cruz, J., Martinez Gregorio, H., Rojas Jimenez, E. A., Romero Cruz, L. E., Mendez Catala, C. F., Alvarez Gomez, R. M., Fragoso Ontiveros, V., Herrera, L. A., Romieu, I., Terrazas, L. I., Chirino, Y. I., Frecha, C., Oliver, J., Perdomo, S., and Vaca Paniagua, F. (2018) Comprehensive Analysis of Germline Variants in Mexican Patients with Hereditary Breast and Ovarian Cancer Susceptibility. Cancers (Basel) 10
15. Owen, D. L., and Farrar, M. A. (2017) STAT5 and CD4 (+) T Cell Immunity. F1000Res 6, 32
16. Schmitt-Ney, M., Happ, B., Hofer, P., Hynes, N. E., and Groner, B. (1992) Mammary gland-specific nuclear factor activity is positively regulated by lactogenic hormones and negatively by milk stasis. Mol Endocrinol 6, 1988-1997
17. Wakao, H., Schmitt-Ney, M., and Groner, B. (1992) Mammary gland-specific nuclear factor is present in lactating rodent and bovine mammary tissue and composed of a single polypeptide of 89 kDa. J Biol Chem 267, 16365-16370
18. Beadling, C., Guschin, D., Witthuhn, B. A., Ziemiecki, A., Ihle, J. N., Kerr, I. M., and Cantrell, D. A. (1994) Activation of JAK kinases and STAT proteins by interleukin-2 and interferon alpha, but not the T cell antigen receptor, in human T lymphocytes. EMBO J 13, 5605-5615
19. Lin, J. X., Migone, T. S., Tsang, M., Friedmann, M., Weatherbee, J. A., Zhou, L., Yamauchi, A., Bloom, E. T., Mietz, J., John, S., and et al. (1995) The role of shared receptor motifs and common Stat proteins in the generation of cytokine pleiotropy and redundancy by IL-2, IL-4, IL-7, IL-13, and IL-15. Immunity 2, 331-339
20. Imada, K., Bloom, E. T., Nakajima, H., Horvath-Arcidiacono, J. A., Udy, G. B., Davey, H. W., and Leonard, W. J. (1998) Stat5b is essential for natural killer cell-mediated proliferation and cytolytic activity. J Exp Med 188, 2067-2074
21. Liu, X., Robinson, G. W., Wagner, K. U., Garrett, L., Wynshaw-Boris, A., and Hennighausen, L. (1997) Stat5a is mandatory for adult mammary gland development and lactogenesis. Genes Dev 11, 179-186
22. Moriggl, R., Topham, D. J., Teglund, S., Sexl, V., McKay, C., Wang, D., Hoffmeyer, A., van Deursen, J., Sangster, M. Y., Bunting, K. D., Grosveld, G. C., and Ihle, J. N. (1999) Stat5 is required for IL-2-induced cell cycle progression of peripheral T cells. Immunity 10, 249-259
23. Teglund, S., McKay, C., Schuetz, E., van Deursen, J. M., Stravopodis, D., Wang, D., Brown, M., Bodner, S., Grosveld, G., and Ihle, J. N. (1998) Stat5a and Stat5b proteins have essential and nonessential, or redundant, roles in cytokine responses. Cell 93, 841-850
24. Cui, Y., Riedlinger, G., Miyoshi, K., Tang, W., Li, C., Deng, C. X., Robinson, G. W., and Hennighausen, L. (2004) Inactivation of Stat5 in mouse mammary epithelium during pregnancy reveals distinct functions in cell proliferation, survival, and differentiation. Mol Cell Biol 24, 8037-8047
25. Yao, Z., Cui, Y., Watford, W. T., Bream, J. H., Yamaoka, K., Hissong, B. D., Li, D., Durum, S. K., Jiang, Q., Bhandoola, A., Hennighausen, L., and O'Shea, J. J. (2006) Stat5a/b are essential for normal lymphoid development and differentiation. Proc Natl Acad Sci U S A 103, 1000-1005
26. Ito, M., Yamazaki, S., Yamagami, K., Kuno, M., Morita, Y., Okuma, K., Nakamura, K., Chida, N., Inami, M., Inoue, T., Shirakami, S., and Higashi, Y. (2017) A novel JAK inhibitor, peficitinib, demonstrates potent efficacy in a rat adjuvant-induced arthritis model. J Pharmacol Sci 133, 25-33
27. Johnston, J. A., Bacon, C. M., Finbloom, D. S., Rees, R. C., Kaplan, D., Shibuya, K., Ortaldo, J. R., Gupta, S., Chen, Y. Q., Giri, J. D., and et al. (1995) Tyrosine phosphorylation and activation of STAT5, STAT3, and Janus kinases by interleukins 2 and 15. Proc Natl Acad Sci U S A 92, 8705-8709
28. Willerford, D. M., Chen, J., Ferry, J. A., Davidson, L., Ma, A., and Alt, F. W. (1995) Interleukin-2 receptor alpha chain regulates the size and content of the peripheral lymphoid compartment. Immunity 3, 521-530
29. Kennell, A. S., Gould, K. G., and Salaman, M. R. (2014) Proliferation assay amplification by IL-2 in model primary and recall antigen systems. BMC research notes 7, 662
30. Wakao, H., Harada, N., Kitamura, T., Mui, A. L., and Miyajima, A. (1995) Interleukin 2 and erythropoietin activate STAT5/MGF via distinct pathways. EMBO J 14, 2527-2535
31. Ju, W., Zhang, M., Jiang, J. K., Thomas, C. J., Oh, U., Bryant, B. R., Chen, J., Sato, N., Tagaya, Y., Morris, J. C., Janik, J. E., Jacobson, S., and Waldmann, T. A. (2011) CP-690,550, a therapeutic agent, inhibits cytokine-mediated Jak3 activation and proliferation of T cells from patients with ATL and HAM/TSP. Blood 117, 1938-1946
32. John, S., Vinkemeier, U., Soldaini, E., Darnell, J. E., Jr., and Leonard, W. J. (1999) The significance of tetramerization in promoter recruitment by Stat5. Mol Cell Biol 19, 1910-1918
33. Owens, T. (1991) Requirement for noncognate interaction with T cells for the activation of B cell immunoglobulin secretion by IL-2. Cellular immunology 133, 352-366
34. Gaida, K., Salimi-Moosavi, H., Subramanian, R., Almon, V., Knize, A., Zhang, M., Lin, F. F., Nguyen, H. Q., Zhou, L., Sullivan, J. K., Wong, M., and McBride, H. J. (2015) Inhibition of CRAC with a human anti-ORAI1 monoclonal antibody inhibits T-cell-derived cytokine production but fails to inhibit a T-cell-dependent antibody response in the cynomolgus monkey. Journal of immunotoxicology 12, 164-173
35. Heidt, S., Roelen, D. L., Eijsink, C., Eikmans, M., van Kooten, C., Claas, F. H., and Mulder, A. (2010) Calcineurin inhibitors affect B cell antibody responses indirectly by interfering with T cell help. Clin Exp Immunol 159, 199-207

Appendix 1

List of MIEs in this AOP

List of Key Events in the AOP

List of Adverse Outcomes in this AOP

Appendix 2

List of Key Event Relationships in the AOP