Sex hormones and gender disparity in immunity and autoimmunity

Elena Ortona1, Federica Delunardo1, Angela Maselli1, Marina Pierdominici1, and Walter Malorni2

1. Section of Biomarkers in Degenerative Diseases, Istituto Superiore di Sanità, Rome, Italy;

2. Section of Gender Medicine, Istituto Superiore di Sanità, Rome, Italy

Received 26 October 2015; accepted 18 November 2015.

Summary. Homeostasis of the human immune system is regulated by multiple factors whose alterations may result in pathological conditions. These factors include the sex hormones that affect both phenotype and function of immune cells through interaction with specific receptors expressed by these cells. In particular, activation of sex hormone receptors by hormone binding may impact many biological processes such as immune cell differentiation and maintenance of immune homeostasis. In turn, they are involved in the pathogenesis of a wide spectrum of diseases, including autoimmune disorders. The different regulatory activity of sex hormones in both sexes results in immune dimorphism. Although it has been suggested that estrogens may enhance immune reactions, while androgens and progesterone may reduce immune system function, the mechanisms underlying this scenario are far from being elucidated. This review discusses the regulatory activity of sex hormones on the immune system and their potential involvement in the onset, progression and outcome of autoimmune diseases.

Key words. Immunity, autoimmunity, sex hormones, estrogens, androgens, progesterone.

Ormoni sessuali e differenze di genere nell’immunità e nell’autoimmunità

Riassunto. La maggior parte delle malattie autoimmuni tende a colpire in misura maggiore le donne rispetto agli uomini. I meccanismi che sono alla base di tale differenza ancora non sono del tutto noti. Tra i fattori responsabili ci sono le differenze genetiche (cromosoma X e Y) e ambientali, ma soprattutto viene attribuita sempre maggiore importanza al ruolo svolto dagli ormoni sessuali. Infatti, gli ormoni sessuali sembrano avere una cruciale funzione di modulare il sistema immunitario influenzando sia l’insorgenza che la cronicizzazione e il decorso delle malattie autoimmuni. Le donne, fisiologicamente, presentano maggiori livelli di estrogeni e progesterone (che rappresentano gli ormoni sessuali femminili) rispetto agli uomini che al contrario hanno più elevati livelli di testosterone e dei suoi derivati (ormoni sessuali maschili). Gli ormoni sessuali femminili e maschili hanno una diretta influenza sulle cellule del sistema immunitario che esprimono recettori ormonali specifici, spesso agendo in senso opposto e modificando sia qualitativamente sia quantitativamente molte caratteristiche della risposta immune.

Parole chiave. Immunità, autoimmunità, ormoni sessuali, estrogeni, androgeni, progesterone.

Introduction

Sex-based disparity in immune responses is well documented and the interplay of sex hormones and immunity is a well-studied phenomenon1,2. It may be explained by intrinsic genetic differences between males and females and/or by the differential levels of specific sex hormones produced by males and females. Evidence pointing towards a significant role for sex hormones has been provided by human and animal studies on hormone manipulation. It has been shown on several circumstances that females respond better than males to pathogenic infections and vaccination programs both in mouse models and clinical studies. Moreover, women display a higher prevalence of the majority of autoimmune diseases as opposed to men (e.g., systemic lupus erythematosus, SLE), but some autoimmune diseases appear indifferently in the two sexes (e.g., Behçet disease) while only few of them are more common in males (e.g., Type 1 diabetes mellitus) (Figure 1).

Gender disparity in immune response

Women show greater antigen presenting activity and mitogenic responses, higher immunoglobulin levels and more enhanced antibody production than males2. The immune system in women tends to generate a Th1 response characterized by pro-inflammatory cytokines and cytotoxic T lymphocytes, except during pregnancy when the immune system shifts towards a Th2 response.

It is well established that sex hormones modulate immune response through the interaction with specific hormone receptors expressed by immune cells and also play an important role as modulators of the onset/perpetuation of autoimmune diseases. Generally, steroid hormones exert an opposite role on the immune response, with estrogens as enhancers of humoral immunity and androgens and progesterone as natural immunosuppressants. Notably, estrogens, androgens and progesterone are found in both males and females, although at different levels, and their effects depend on their concentration levels and the type of target immune cell.




Androgens

Androgens act through the androgen receptor (AR), from the NR3C4 gene located on chromosome X. Intracellular ARs are present in bone marrow stromal cells3, thymocytes4 and immature dendritic cells (DCs)5,6. Splenic T cells and macrophages express a membrane form of AR7. The action of androgens on immune function may vary depending on the type of androgen used, the dose administered, and the timing of administration8. For example, some studies report immunosuppressive effects9-11, whereas endogenous androgens are also thought to be immunostimulatory12. Testosterone, the primary and best known androgen, has been implicated as a regulator of the immune response to viruses, vaccines, host tissue, and cancer. Despite the relevance of these pleiotropic effects, the mechanisms underlying the activity of testosterone on the immune system are not well understood. Testosterone may suppress the expression of the pro-inflammatory cytokines TNF-α, interleukin (IL)-1β and IL-6 and potentiate the expression of the anti-inflammatory cytokine IL-1013. Testosterone inhibits Th1 differentiation by up-regulating type 1 protein tyrosine phosphatase (Ptpn1) in both mice and humans14, reduces the proliferation and differentiation of lymphocytes15-17 and may suppress immunoglobulin production, in particular IgA12. Supraphysiological doses of testosterone may inhibit the cytotoxic activity of natural killer (NK) cells18-20. Overall, these data strongly support an immunosuppressive role for androgens although, since their effects may vary considerably depending on the level of exposure, the potential role of these hormones in gender-specific immune function is still unknown.

Progesterone

Progesterone has three isoforms of receptors (PRs) PR-A, PR-B, and PR-C, from the NR3C3 gene located on chromosome 11. To date, progesterone is found to have two intracellular receptors (iPRs) and three membrane receptors (mPR) of which two isoforms of each receptor type are found in humans [iPRA, iPRB, membrane PRα (mPRα), and mPRβ]21-24. The wide distribution of PRs in immune cells, including granulocytes, NK cells, DCs, T cells and B cells, indicates that progesterone impacts both the innate and adaptive immune systems21. Intracellular or nuclear progesterone receptor expression on lymphocytes was initially described in pregnant women25. In addition to playing a critical role in gestation, iPR, activated by low-physiologic concentrations of progesterone, is thought to suppress antibody responses in both sexes26. More recently, mPRα has been detected in T cells of non-pregnant women, and appears to be upregulated during the luteal phase on CD8+, but not on CD4+ T lymphocytes23. It is known that it suppresses Th1/Th17 and favors Th2 type cytokine secretions, inhibits the cytotoxicity of T cells and increases the differentiation of Th0 cells as T regulatory cells (Tregs). Similarly, an inhibitory effect is exerted by progesterone on the activities of NK cells, e.g., inhibition of IFN-γ production and apoptosis induction27. Other known effects include the inhibition of macrophage activity28, the modulation of myeloid DC activity29, the inhibition of glucocorticoid-mediated thymocyte apoptosis30, the reduction of nitric oxide production31, and the expression of toll-like receptors by macrophages32.

Estrogens

Estrogens modulate the immune system contributing to significant modifications in immune function during the menstrual cycle and pregnancy. They also impact infectious and autoimmune diseases as well as inflammation33-36. Estrogens, in particular 17β estradiol (E2), are able to regulate immune responses acting at multiple levels, including cell development, proliferation, cytokine or antibody production, and apoptosis. Regulation of both proliferation and apoptosis is of particular importance in the development of an appropriate T and B cell repertoire and in the preservation of immune homeostasis, eluding abnormal clonal expansion of autoreactive immune cells37. E2 interacts with two receptors, estrogen receptor (ER)α and ERβ, from NR3A1 and NR3A2 genes located on chromosome 6 and 14, respectively. All immune cell types express intracellular ER and the presence of one ER subtype over the other might change estrogen effects, promoting or dampening inflammation33,36,38,39. ERα activation plays a predominant and immunostimulatory role40,41 while ERβ activation appears to have a slightly immunosuppressive effect39. Our group has recently demonstrated the intracellular expression of both ERα and ERβ in human peripheral T and B lymphocytes, and in NK cells42. Notably, intracellular ER levels are not menstrual cycle-dependent and do not decrease with age in cycling females43.

As stated above, E2 influences the development of both B and T cells. For example, it appears to favor the survival of high-affinity DNA-reactive B cells at both the immature and transitional B cell stages facilitating the maturation of a potentially pathogenic naive autoreactive B cell repertoire44,45. Several studies have demonstrated a role for E2 in the thymus (including thymic involution) and early T cell development46-48. The effects of E2 on mature immune cells are quite complex. In short, at periovulatory to pregnancy levels (500 pg/ml-50ng/ml)49, E2 inhibits proinflammatory pathways such as tumor necrosis factor (TNF)-α, IL-1β, IL-6 production, and activity of NK cells; it is also able to stimulate antiinflammatory pathways such as IL-4, IL-10, and transforming growth factor-β production38. Conversely, at lower concentrations, E2 stimulates TNF-α, IFN-γ, IL-1β, and the activity of NK cells. E2 is capable of stimulating antibody production by B cells both at high and low concentrations38. Interestingly, a recent study showed that E2 induces in B cells the expression of activation-induced deaminase, a protein that drives antibody diversification, transforming benign antibodies into autoantibodies, thus favoring autoimmunity50. E2 is also able to play an immunoregulatory role, increasing the number and function of CD4+CD25+ Tregs51,52.

The discovery of plasma membrane-associated ERα (mERα) in different cell types has greatly expanded the understanding of estrogen action53. Membrane ERα rapidly activates different protein kinase cascades influencing downstream transcription factors to produce non-genomic effects; at the same time it can modulate intracellular ER action through the phosphorylation of intracellular ERs and their coactivators54. With regard to mER expression in immune cells, previously reported data obtained using a membrane-impermeant form of E2 (i.e., E2 conjugated with bovine serum albumin) indicated that an estrogen-binding protein exists in the plasma membrane of human lymphoblastoid B cells55-57. The cell surface expression of a functionally active ERα isoform, but not of ERβ, has also been found in the plasma membrane of lymphocytes, demonstrating that E2 level fluctuations may be associated with a prompt lymphocyte response42. Recently, our research team showed the presence of anti-ERα antibodies (Abs), but not of anti-ERβ Abs, in sera from patients with two paradigmatic autoimmune diseases, characterized by a high female-to-male ratio, i.e., SLE and systemic sclerosis58,59. These antibodies behave as true ERα agonists activating ERK signaling and significantly correlate with disease activity and severity. Further studies are needed to gain greater insight into mER expression and its signal transduction pathways in different lymphocyte subpopulations.

Conclusions

Estrogens, progesterone and androgens are crucial regulators of the immune system. The major effects of sex hormones on immune cells have been summarized in Table 1. The mechanisms behind sex hormone influences on immune functions are attributed to their interactions with the receptors expressed on the immune cells, which affect the production, maturation, differentiation, and, ultimately, the functioning of the immune system, also influencing the development of immune-related diseases. In fact, for most autoimmune diseases there are clear sex-related differences in prevalence whereby women are generally more frequently affected than men (Figure 1).

In conclusion, understanding the effects of the sex hormones on immune-mediated diseases could lead to the identification of innovative and readily available therapeutic interventions, such as hormone antagonists or agonists, to manage autoimmune diseases.







References

1. Ortona E, Margutti P, Matarrese P, et al. Redox state, cell death and autoimmune diseases: a gender perspective. Autoimmun Rev 2008; 7: 579-84.

2. Zandman-Goddard G, Peeva E, Shoenfeld Y. Gender and autoimmunity. Autoimmun Rev 2007; 6: 366-72.

3. Bellido T, Jilka RL, Boyce BF, et al. Regulation of interleukin-6, osteoclastogenesis, and bone mass by androgens. The role of the androgen receptor. J Clin Invest 1995; 95: 2886-95.

4. Kovacs W, Olsen N. Androgen receptors in human thymocytes. J Immunol 1987; 139: 490-3.

5. Butts C, Bowers E, Horn C, et al. Inhibitory effects of progesterone differ in dendritic cells from female and male rodents. Gender Med 2008; 5: 434-47.

6. Martocchia A, Stefanelli M, Cola S, et al. Sex steroids in autoimmune diseases. Curr Top Med Chem 2011; 11: 1668-83.

7. Benten WP, Lieberherr M, Stamm O, et al. Testosterone signaling through internalizable surface receptors in androgen receptor-free macrophages. Mol Biol Cell 1999; 10: 3113-23.

8. Ngo ST, Steyn FJ, McCombe PA. Gender differences in autoimmune disease. Front Neuroendocrinol 2014; 35: 347-69.

9. Fujii H, Nawa Y, Tsuchiya H, et al. Effect of a single administration of testosterone on the immune response and lymphoid tissues in mice. Cell Immunol 1975; 20: 315-26.

10. Olsen NJ, Kovacs WJ. Gonadal steroids and immunity. Endocr Rev 1996; 17: 369-84.

11. Paavonen T. Hormonal regulation of immune responses. Ann Med 1994; 26: 255-58.

12. Calabrese LH, Kleiner SM, Barna BP, et al. The effects of anabolic steroids and strength training on the human immune response. Med Sci Sports Exerc 1989; 21: 386-92.

13. Cutolo M, Wilder RL. Different roles for androgens and estrogens in the susceptibility to autoimmune rheumatic diseases. Rheum Dis Clin North Am 2000; 26: 825-39.

14. Kissick HT, Martin GS, Laura KD, et al. Androgens alter T-cell immunity by inhibiting T-helper 1 differentiation. PNAS 2014; 111: 9887-92.

15. Sakiani S, Olsen NJ, Kovacs WJ. Gonadal steroids and humoral immunity. Nat Rev Endocrinol 2013; 9: 56-62.

16. Sthoeger ZM, Chiorazzi N, Lahita RG. Regulation of the immune response by sex hormones. I. In vitro effects of estradiol and testosterone on pokeweed mitogen-induced human B cell differentiation. J Immunol 1988; 141: 91-8.

17. Trigunaite A, Dimo J, Jørgensen TN. Suppressive effects of androgens on the immune system. Cell Immunol 2015; 294: 87-94.

18. Callewaert DM, Moudgil VK, Radcliff G, et al. Hormone specific regulation of natural killer cells by cortisol. Direct inactivation of the cytotoxic function of cloned human NK cells without an effect on cellular proliferation. FEBS Lett 1991; 285: 108-10.

19. Marshall-Gradisnik S, Weatherby RP, Deakin GB, et al. Natural killer cell activity following 6 weeks of strength training in healthy young males with/ without testosterone enanthate adminstration. J Exerc Sci Fit 2008; 6: 106-14.

20. Sulke AN, Jones DB, Wood PJ. Hormonal modulation of human natural killer cell activity in vitro. J Reprod Immunol 1985; 7(2): 105-10.

21. Tan IJ, Peeva E, Zandman-Goddard G. Hormonal modulation of the immune system - A spotlight on the role of progestogens. Autoimmun Rev 2015; 14: 536-42.

22. Szekeres-Bartho J, Barakonyi A, Par G, et al. Progesterone as an immunomodulatory molecule. Int Immunopharmacol 2001; 1: 1037-48.

23. Dosiou C, Hamilton AE, Pang Y, et al. Expression of membrane progesterone receptors on human T lymphocytes and Jurkat cells and activation of G proteins by progesterone. J Endocrinol 2008; 196: 67–77.

24. Hughes GC. Progesterone and autoimmune disease. Autoimmun Rev 2012; 11: A502-14.

25. Szekeres-Bartho J, Szekeres G, Debre P, et al. Reactivity of lymphocytes to a progesterone receptor-specific monoclonal antibody. Cell Immunol 1990; 125: 273-83.

26. Hughes GC, Clark EA, Wong AH. The intracellular progesterone receptor regulates CD4+ T cells and T cell-dependent antibody responses. J Leukoc Biol 2013; 93: 369-75.

27. Arruvito L, Giulianelli S, Flores AC, et al. NK cells expressing a progesterone receptor are susceptible to progesterone-induced apoptosis. J Immunol 2008; 180: 5746-53.

28. Pisetsky DS, Spencer DM. Effects of progesterone and estradiol sex hormones on the release of microparticles by RAW 264.7 macrophages stimulated by Poly(I:C). Clin Vaccine Immunol 2011; 18, 1420-6.

29. Hughes GC, Clark EA. Regulation of dendritic cells by female sex steroids: relevance to immunity and autoimmunity. Autoimmunity 2007; 40: 470-81.

30. McMurray RW, Wilson JG, Bigler L, Xiang L, Lagoo A. Progesterone inhibits glucocorticoid-induced murine thymocyte apoptosis. Int J Immunopharmacol 2000; 22: 955-65.

31. Miller L, Alley EW, Murphy WJ, et al. Progesterone inhibits inducible nitric oxide synthase gene expression and nitric oxide production in murine macrophages. J Leukoc Biol 1996; 59: 442-50.

32. Jones LA, Anthony JP, Henriquez FL, et al. Toll-like receptor-4-mediated macrophage activation is differentially regulated by progesterone via the glucocorticoid and progesterone receptors. Immunology 2008; 125: 59-69.

33. Bouman A, Heineman MJ, Faas MM. Sex hormones and the immune response in humans. Hum Reprod Update 2005; 11: 411-23.

34. Pernis AB. Estrogen and CD4+ T cells. Curr Opin Rheumatol 2007; 19: 414-20.

35. Karpuzoglu E, Zouali M. The multi-faceted influences of estrogen on lymphocytes: toward novel immuno-interventions strategies for autoimmunity management. Clin Rev Allergy Immunol 2011; 40: 16-26.

36. Cunningham M, Gilkeson G. Estrogen receptors in immunity and autoimmunity. Clin Rev Allergy Immunol 2011; 40 66-73.

37. Giovannetti A, Pierdominici M, Di Iorio A, et al. Apoptosis in the homeostasis of the immune system and in human immune mediated diseases. Curr Pharm Des 2008; 14 253-68.

38. Straub RH. The complex role of estrogens in inflammation. Endocr Rev 2007; 28: 521-74.

39. Phiel KL, Henderson RA, Adelman SJ, et al. Differential estrogen receptor gene expression in human peripheral blood mononuclear cell populations. Immunol Lett 2005; 97: 107-13.

40. Li J, McMurray RW. Effects of estrogen receptor subtype-selective agonists on autoimmune disease in lupus-prone NZB/NZW F1 mouse model. Clin Immunol 2007; 123: 219-26.

41. Svenson JL, EuDaly J, Ruiz P, Korach KS, Gilkeson GS. Impact of estrogen receptor deficiency on disease expression in the NZM2410 lupus prone mouse. Clin Immunol 2008; 128: 259-68.

42. Pierdominici M, Maselli A, Colasanti T, et al. Estrogen receptor profiles in human peripheral blood lymphocytes. Immunol Lett 2010; 132: 79-85.

43. Rider V, Li X, Peterson G, et al. Differential expression of estrogen receptors in women with systemic lupus erythematosus. J Rheumatol 2006; 33: 1093-101.

44. Grimaldi CM, Cleary J, Dagtas AS, et al. Estrogen alters thresholds for B cell apoptosis and activation. J Clin Invest 2002; 109: 1625-33.

45. Grimaldi CM, Jeganathan V, Diamond B. Hormonal regulation of B cell development: 17 beta-estradiol impairs negative selection of high-affinity DNA-reactive B cells at more than one developmental checkpoint. J Immunol 2006; 176: 2703-10.

46. Erlandsson MC, Ohlsson C, Gustafsson JA, et al. Role of oestrogen receptors alpha and beta in immune organ development and in oestrogen-mediated effects on thymus. Immunology 2001; 103: 17-25.

47. Ryan MR, Shepherd R, Leavey JK, et al. An IL-7-dependent rebound in thymic T cell output contributes to the bone loss induced by estrogen deficiency. Proc Natl Acad Sci USA 2005; 102: 16735-40.

48. Zoller AL, Kersh GJ. Estrogen induces thymic atrophy by eliminating early thymic progenitors and inhibiting proliferation of beta-selected thymocytes. J Immunol 2006; 176: 7371-8.

49. Neill JD. Knobil and Neill’s physiology of reproduction (third ed). New York: Academic Press, 2005.

50. Pauklin S, Sernandez IV, Bachmann G, et al. Estrogen directly activates AID transcription and function. J Exp Med 2009; 206: 99-111.

51. Polanczyk MJ, Carson BD, Subramanian S, et al. Cutting edge: estrogen drives expansion of the CD4+CD25+ regulatory T cell compartment. J Immunol 2004; 173: 2227-30.

52. Aristimuno C, Teijeiro R, Valor L, et al. Sex-hormone receptors pattern on regulatory T-cells: clinical implications for multiple sclerosis. Clin Exp Med 2012; 12: 247-55.

53. Levin ER. Extra-nuclear estrogen receptors roles in physiology: lessons from mouse models. Am J Physiol Endocrinol Metab 2014; 307: E133-40.

54. Zhang D, Trudeau VL. Integration of membrane and nuclear estrogen receptor signaling. Comp Biochem Physiol A Mol Integr Physiol 2006; 144: 306-15.

55. Tubiana N, Mishal Z, le Caer F, et al. Quantification of oestradiol binding at the surface of human lymphocytes by flow cytofluorimetry. Br J Cancer 1986; 54: 501-4.

56. Ortona E, Pierdominici M, Berstein L. Autoantibodies to estrogen receptors and their involvement in autoimmune diseases and cancer. J Steroid Biochem Mol Biol 2014; 144 Pt B: 260-7.

57. Maselli A, Pierdominici M, Vitale C, Ortona E. Membrane lipid rafts and estrogenic signalling: a functional role in the modulation of cell homeostasis. Apoptosis 2015; 20: 671-8.

58. Colasanti T, Maselli A, Conti F, et al. Autoantibodies to estrogen receptor alpha interfere with T lymphocyte homeostasis and are associated with disease activity in systemic lupus erythematosus. Arthritis Rheum 2012; 64: 778-87.

59. Giovannetti A, Maselli A, Colasanti T, et al. Autoantibodies to estrogen receptor alpha in systemic sclerosis (SSc) as pathogenetic determinants and markers of progression. PLoS One 2013; 8: e74332.