International Journal of Rheumatic Diseases 2015; 18: 379–381
EDITORIAL
B cells and rheumatoid factors in autoimmunity In the current issue of this journal two very different research studies are published that relate to the possible roles that rheumatoid factor (RF) and B cells play in autoimmunity. In the article by McComish et al.,1 a cross-sectional analysis of various peripheral blood B cell subsets in a cohort of patients with rheumatoid arthritis (RA) was carried out. Patients at diagnosis and not on treatment (disease-modifying anti-rheumatic drug [DMARD]na€ıve) were compared with patients on treatment and both groups of patients compared with normal controls. The authors then studied if any of the changes observed reflected how active the disease was, response to treatment, whether patients had high titre anti-cyclic citrullinated peptide antibodies (anti-CCP) at diagnosis or to what extent some of the differences could be explained by differences in age and sex between the groups. In view of the well known importance of B cells in the pathogenesis of RA, studying changes in the peripheral blood B cell subsets could reflect changes in B cell homeostasis associated with the disease and could be used as a biomarker of patient characteristics and their responses to treatment. In summary, the study found that various B cell subsets (mainly memory B cell subsets) were reduced at diagnosis when compared with controls, with further decreases seen in patients on treatment with DMARDs. The authors found lower proportion and numbers of total memory and unswitched memory B cell subsets in patients at diagnosis. Patients on treatment showed further decreases in total numbers of these subsets and also of switched memory, CD21 low and transitional B cells and of plasmablasts. However, patients on treatment had lower proportion and number of total B cells and many of the differences between the two patient groups could be due to this as proportions were not significantly different except for plasmablasts. There was some suggestion that changes in particular subsets may be associated with response to therapy, need for more intensive therapy or the therapy itself. Good response to treatment and a state of remission or low disease activity as defined by the Disease Activity Score of 28
joints (DAS28) was associated with lower switched memory and immunoglobulin M (IgM)-only memory B cells. High anti-CCP antibodies were associated with lower unswitched memory B cell subsets in both subgroups of patients and also with lower switched memory B cells in the DMARD-na€ıve group. Some of the differences could be due at least partially to differences in age between the cohorts. The authors have an error in methodology but this probably does not affect the results. Their statement regarding CD38 expression on the different B cell subpopulations is not correct.1–3. Despite this error and the absence of any example of gating strategy for the readers to check, the use of CD27 to characterize memory B cell populations and the fact that the percentages of plasmablasts and transitional B cells are what would be expected means that the results are probably correct. There are only a small number of studies looking at peripheral blood B cell subsets in patients with RA outside the context of patients treated with B cell depletion therapy. Previous studies found also decreased unswitched memory B cells but also an increase in switched memory B cells with increased disease duration.2,4 In early arthritis, short-term treatment with methotrexate and corticosteroids was not associated with changes in peripheral blood B cell subsets.5 Treatment with antitumor necrosis factor (TNF) agents in patients with established arthritis was associated with an increase in unswitched memory B cells.4 We do not know where the majority of pathogenic B cells reside in RA and to what extent they circulate in the peripheral blood. Samuels et al.6 have documented the presence of RF- and CCP-specific circulating B cells in patients with RA. Older studies had shown ex vivo spontaneous production of RF by peripheral blood mononuclear cells and changes in response to treatment.7 Early flare following B cell depletion with rituximab is associated with repopulation with relatively higher proportions of circulating memory B cells.8 Usually, as in the current study, changes in peripheral blood B cell subsets in RA are interpreted as mirroring or being the reverse of what happens in the RA synovia.
© 2015 Asia Pacific League of Associations for Rheumatology and Wiley Publishing Asia Pty Ltd
Editorial
However, there is strong evidence that many of the pathogenic B cell clones in RA are unlikely to be in the synovia. Presence of disease-specific autoantibodies in sera precedes, sometimes for many years, any sign of inflammation in the synovia, and many patients with RA do not have significant numbers of B cells present in the synovial tissue.9,10 Memory B cell subsets can be decreased in DMARD-na€ıve RA patients because of decreased formation, activation, differentiation or survival of B cells and not only because they may migrate and be retained in the inflamed synovia. Interestingly, as the authors point out, changes found in circulating B cell subsets do not normalize following treatment.1 Even taking into account that some of the changes seen on treatment could be associated with the therapies themselves, this suggests that changes in circulating B cell subsets may reflect changes in B cell homeostasis in RA that are directly related to perpetuation of the disease, if not initiation. In contrast, Beduleva et al.11 present a very different study showing how particular subspecies of RFs can play a protective role in animal models of autoimmunity, including collagen-induced arthritis (CIA). This is an extension of early studies from the same group.12 Their hypothesis is that certain subspecies of RFs produced in animals that prove to be resistant to clinical disease are involved in regulating the immune response to the autoimmune disease-inducing antigens via idiotype– anti-idiotype interactions with lymphocytes specific for those antigens. Production of these RFs occurred early in the immune response and seemed to be independent of T cell help. These RFs did not recognize IgG in immune complexes. They also showed that it was possible to induce production of similar RFs by immunization of the animals with papain Fc fragments of homologous IgG and the authors go on to suggest a therapeutic potential for such RFs in autoimmunity. Agglutination of IgG-loaded erythrocytes was used to detect RFs in these experiments to allow detection of RF specific to homologous IgG and also because RFs detectable by this method can be seen in intact rats and are therefore thought to be part of the natural autoantibody pool. Using animal models of autoantigeninduced autoimmune diseases that included models of CIA, encephalomyelitis (EAE) and atherosclerosis, the authors showed that RFs produced during the initiation phase of the autoimmune response were associated with resistance to developing clinical disease. In addition, termination of the immune response in CIA-resistant rats and in EAE-resistant rats and also remission and reduction of autoantibodies in CIA- and EAE-
380
affected rats coincided with peak blood RF levels, in particular in the EAE model. Competitive enzyme-linked immunosorbent assays showed that RF produced in these circumstances was able to specifically and competitively inhibit antigenantibody reactions to the specific antigen involved, suggesting that it could recognize epitopes in or around the antigen-binding site. This was seen with each of the three antigens (collagen type II, myelin basic protein and low-density lipoprotein). When RF-containing sera was studied against anti-sera specific to a different antigen, binding was inhibited but this inhibition was noncompetitive and non-specific. This showed that RFs developed differently in an immune response to different antigens and that RFs in this setting were not recognizing immune complexes, but specific and also shared idiotopes on the different autoimmunity-inducing autoantibodies. The specific idiotopes were presumed to be located in the antigen-binding region of the autoimmunity-inducing antibodies. This is different from the generally accepted role of RF produced during immune reactions presumed to play an important role in immune complex clearance. Animal models of human disease have many limitations and we do not know to what extent (if at all) they reflect what happens in human disease. Nevertheless, these studies do show how heterogeneous and unexpected autoantibody responses can be. One of the more interesting unexplained characteristics of the autoimmune response in RA is the existence of the two autoantibody systems, that is, RFs and autoantibodies against citrullinated peptide antigens (ACPAs). It is likely that some kind of relationship exists between the two systems. Most patients who have seropositive RA have both types of autoantibodies detectable in the serum and their presence precedes clinical disease, with some studies suggesting that ACPA precedes RF.9 Both responses are polyclonal and bear the characteristics of being antigen-driven.13,14 Both autoantibodies are associated with disease prognosis. Patients with RA have increased numbers of circulating B cells with RF and anti-CCP specificities than normal controls.9 It is possible that RFs arise in some way in response to the presence of immune complexes that are ACPA-based, but the well-known differences between RFs in RA and ‘physiological’ RFs that are often seen after immunization or infections and thought to contribute to immune complex clearance, make such a simple relationship an unlikely explanation. The current study by Bedulova et al.11 shows how antibodies that show RF activity can be so heterogeneous and reminds us that we will proba-
International Journal of Rheumatic Diseases 2015; 18: 379–381
Editorial
bly have to think well outside the box if we ever are going to be able to grasp the relationship between the two autoantibody systems in RA and have a better idea of perpetuation and potential initiation mechanisms of the autoimmune response in RA. M. LEANDRO Centre for Rheumatology Research, Department of Medicine, University College London, London, UK Email: [email protected]
REFERENCES 1 McComish J, Mundy J, Sullivan T et al. (2014) Changes in peripheral blood B cell subsets at diagnosis and after treatment with disease-modifying anti-rheumatic drugs in patients with rheumatoid arthritis: correlation with clinical and laboratory parameters. Int J Rheum Dis 18, 421–32. 2 Bohnhorst JO, Bjorgan MB, Thoen JE et al. (2001) Bm1-Bm5 classification of peripheral blood B cells reveals circulating germinal center founder cells in healthy individuals and disturbance in the B cell subpopulations in patients with primary Sjogren’s syndrome. J Immunol 167, 3610–8. 3 Sims GP, Ettinger R, Shirota Y, et al. (2005) Identification and characterization of circulating transitional B cells. Blood 105, 4390–8. 4 Souto-Carneiro MM, Mahadevan V, Takada K et al. (2009) Alterations in peripheral blood memory B cells in patients with active rheumatoid arthritis are dependent on the action of tumour necrosis factor. Arthritis Res Ther 11, R84.
International Journal of Rheumatic Diseases 2015; 18: 379–381
5 Moura RA, Weinmann P, Pereira PA et al. (2010) Alterations on peripheral blood B-cell subpopulations in very early arthritis patients. Rheumatology 49, 1082–92. 6 Samuels J, Ng Y-S, Coupillaud C et al. (2005) Impaired early B cell tolerance in patients with rheumatoid arthritis. JEM 201, 1659–67. 7 Olsen NJ, Callahan LF, Pincus T (1988) In vitro rheumatoid factor synthesis in patients taking second-line drugs for rheumatoid arthritis. Independent associations with disease activity. Arthritis Rheum 31, 1090–6. 8 Leandro MJ, Cambridge G, Ehrenstein ME et al. (2006) Reconstitution of peripheral blood B cells after depletion with rituximab in patients with rheumatoid arthritis. Arthritis Rheum 54, 613–20. 9 Nielen MMJ, van Schaardenburg D, Reesink HW et al. (2004) Specific autoantibodies precede the symptoms of rheumatoid arthritis: a study of serial measurements in blood donors. Arthritis Rheum 50, 380–6. 10 Thurlings RM, Wijbrandts CA, Mebius RE et al. (2008) Synovial lymphoid neogenesis does not define a specific clinical rheumatoid arthritis phenotype. Arthritis Rheum 58, 1582–9. 11 Beduleva L, Menshikov I, Stolyarova E et al. (2014) Rheumatoid factor in idiotypic regulation of autoimmunity. Int J Rheum Dis 18, 408–20. 12 Beduleva L, Menshikov I (2010) Role of idiotype-anti-idiotype interactions in the induction of collagen-induced arthritis in rats. Immunobiology 215, 963–70. 13 Jefferis R (1995) Rheumatoid factors, B cells and immunoglobulin genes. Br Med Bull 51, 312–31. 14 Amara K, Steen J, Murray F et al. (2013) Monoclonal IgG antibodies generated from joint-derived B cells of RA patients have a strong bias toward citrullinated autoantigen recognition. J Exp Med 210, 445–55.
381
EDITORIAL
B cells and rheumatoid factors in autoimmunity In the current issue of this journal two very different research studies are published that relate to the possible roles that rheumatoid factor (RF) and B cells play in autoimmunity. In the article by McComish et al.,1 a cross-sectional analysis of various peripheral blood B cell subsets in a cohort of patients with rheumatoid arthritis (RA) was carried out. Patients at diagnosis and not on treatment (disease-modifying anti-rheumatic drug [DMARD]na€ıve) were compared with patients on treatment and both groups of patients compared with normal controls. The authors then studied if any of the changes observed reflected how active the disease was, response to treatment, whether patients had high titre anti-cyclic citrullinated peptide antibodies (anti-CCP) at diagnosis or to what extent some of the differences could be explained by differences in age and sex between the groups. In view of the well known importance of B cells in the pathogenesis of RA, studying changes in the peripheral blood B cell subsets could reflect changes in B cell homeostasis associated with the disease and could be used as a biomarker of patient characteristics and their responses to treatment. In summary, the study found that various B cell subsets (mainly memory B cell subsets) were reduced at diagnosis when compared with controls, with further decreases seen in patients on treatment with DMARDs. The authors found lower proportion and numbers of total memory and unswitched memory B cell subsets in patients at diagnosis. Patients on treatment showed further decreases in total numbers of these subsets and also of switched memory, CD21 low and transitional B cells and of plasmablasts. However, patients on treatment had lower proportion and number of total B cells and many of the differences between the two patient groups could be due to this as proportions were not significantly different except for plasmablasts. There was some suggestion that changes in particular subsets may be associated with response to therapy, need for more intensive therapy or the therapy itself. Good response to treatment and a state of remission or low disease activity as defined by the Disease Activity Score of 28
joints (DAS28) was associated with lower switched memory and immunoglobulin M (IgM)-only memory B cells. High anti-CCP antibodies were associated with lower unswitched memory B cell subsets in both subgroups of patients and also with lower switched memory B cells in the DMARD-na€ıve group. Some of the differences could be due at least partially to differences in age between the cohorts. The authors have an error in methodology but this probably does not affect the results. Their statement regarding CD38 expression on the different B cell subpopulations is not correct.1–3. Despite this error and the absence of any example of gating strategy for the readers to check, the use of CD27 to characterize memory B cell populations and the fact that the percentages of plasmablasts and transitional B cells are what would be expected means that the results are probably correct. There are only a small number of studies looking at peripheral blood B cell subsets in patients with RA outside the context of patients treated with B cell depletion therapy. Previous studies found also decreased unswitched memory B cells but also an increase in switched memory B cells with increased disease duration.2,4 In early arthritis, short-term treatment with methotrexate and corticosteroids was not associated with changes in peripheral blood B cell subsets.5 Treatment with antitumor necrosis factor (TNF) agents in patients with established arthritis was associated with an increase in unswitched memory B cells.4 We do not know where the majority of pathogenic B cells reside in RA and to what extent they circulate in the peripheral blood. Samuels et al.6 have documented the presence of RF- and CCP-specific circulating B cells in patients with RA. Older studies had shown ex vivo spontaneous production of RF by peripheral blood mononuclear cells and changes in response to treatment.7 Early flare following B cell depletion with rituximab is associated with repopulation with relatively higher proportions of circulating memory B cells.8 Usually, as in the current study, changes in peripheral blood B cell subsets in RA are interpreted as mirroring or being the reverse of what happens in the RA synovia.
© 2015 Asia Pacific League of Associations for Rheumatology and Wiley Publishing Asia Pty Ltd
Editorial
However, there is strong evidence that many of the pathogenic B cell clones in RA are unlikely to be in the synovia. Presence of disease-specific autoantibodies in sera precedes, sometimes for many years, any sign of inflammation in the synovia, and many patients with RA do not have significant numbers of B cells present in the synovial tissue.9,10 Memory B cell subsets can be decreased in DMARD-na€ıve RA patients because of decreased formation, activation, differentiation or survival of B cells and not only because they may migrate and be retained in the inflamed synovia. Interestingly, as the authors point out, changes found in circulating B cell subsets do not normalize following treatment.1 Even taking into account that some of the changes seen on treatment could be associated with the therapies themselves, this suggests that changes in circulating B cell subsets may reflect changes in B cell homeostasis in RA that are directly related to perpetuation of the disease, if not initiation. In contrast, Beduleva et al.11 present a very different study showing how particular subspecies of RFs can play a protective role in animal models of autoimmunity, including collagen-induced arthritis (CIA). This is an extension of early studies from the same group.12 Their hypothesis is that certain subspecies of RFs produced in animals that prove to be resistant to clinical disease are involved in regulating the immune response to the autoimmune disease-inducing antigens via idiotype– anti-idiotype interactions with lymphocytes specific for those antigens. Production of these RFs occurred early in the immune response and seemed to be independent of T cell help. These RFs did not recognize IgG in immune complexes. They also showed that it was possible to induce production of similar RFs by immunization of the animals with papain Fc fragments of homologous IgG and the authors go on to suggest a therapeutic potential for such RFs in autoimmunity. Agglutination of IgG-loaded erythrocytes was used to detect RFs in these experiments to allow detection of RF specific to homologous IgG and also because RFs detectable by this method can be seen in intact rats and are therefore thought to be part of the natural autoantibody pool. Using animal models of autoantigeninduced autoimmune diseases that included models of CIA, encephalomyelitis (EAE) and atherosclerosis, the authors showed that RFs produced during the initiation phase of the autoimmune response were associated with resistance to developing clinical disease. In addition, termination of the immune response in CIA-resistant rats and in EAE-resistant rats and also remission and reduction of autoantibodies in CIA- and EAE-
380
affected rats coincided with peak blood RF levels, in particular in the EAE model. Competitive enzyme-linked immunosorbent assays showed that RF produced in these circumstances was able to specifically and competitively inhibit antigenantibody reactions to the specific antigen involved, suggesting that it could recognize epitopes in or around the antigen-binding site. This was seen with each of the three antigens (collagen type II, myelin basic protein and low-density lipoprotein). When RF-containing sera was studied against anti-sera specific to a different antigen, binding was inhibited but this inhibition was noncompetitive and non-specific. This showed that RFs developed differently in an immune response to different antigens and that RFs in this setting were not recognizing immune complexes, but specific and also shared idiotopes on the different autoimmunity-inducing autoantibodies. The specific idiotopes were presumed to be located in the antigen-binding region of the autoimmunity-inducing antibodies. This is different from the generally accepted role of RF produced during immune reactions presumed to play an important role in immune complex clearance. Animal models of human disease have many limitations and we do not know to what extent (if at all) they reflect what happens in human disease. Nevertheless, these studies do show how heterogeneous and unexpected autoantibody responses can be. One of the more interesting unexplained characteristics of the autoimmune response in RA is the existence of the two autoantibody systems, that is, RFs and autoantibodies against citrullinated peptide antigens (ACPAs). It is likely that some kind of relationship exists between the two systems. Most patients who have seropositive RA have both types of autoantibodies detectable in the serum and their presence precedes clinical disease, with some studies suggesting that ACPA precedes RF.9 Both responses are polyclonal and bear the characteristics of being antigen-driven.13,14 Both autoantibodies are associated with disease prognosis. Patients with RA have increased numbers of circulating B cells with RF and anti-CCP specificities than normal controls.9 It is possible that RFs arise in some way in response to the presence of immune complexes that are ACPA-based, but the well-known differences between RFs in RA and ‘physiological’ RFs that are often seen after immunization or infections and thought to contribute to immune complex clearance, make such a simple relationship an unlikely explanation. The current study by Bedulova et al.11 shows how antibodies that show RF activity can be so heterogeneous and reminds us that we will proba-
International Journal of Rheumatic Diseases 2015; 18: 379–381
Editorial
bly have to think well outside the box if we ever are going to be able to grasp the relationship between the two autoantibody systems in RA and have a better idea of perpetuation and potential initiation mechanisms of the autoimmune response in RA. M. LEANDRO Centre for Rheumatology Research, Department of Medicine, University College London, London, UK Email: [email protected]
REFERENCES 1 McComish J, Mundy J, Sullivan T et al. (2014) Changes in peripheral blood B cell subsets at diagnosis and after treatment with disease-modifying anti-rheumatic drugs in patients with rheumatoid arthritis: correlation with clinical and laboratory parameters. Int J Rheum Dis 18, 421–32. 2 Bohnhorst JO, Bjorgan MB, Thoen JE et al. (2001) Bm1-Bm5 classification of peripheral blood B cells reveals circulating germinal center founder cells in healthy individuals and disturbance in the B cell subpopulations in patients with primary Sjogren’s syndrome. J Immunol 167, 3610–8. 3 Sims GP, Ettinger R, Shirota Y, et al. (2005) Identification and characterization of circulating transitional B cells. Blood 105, 4390–8. 4 Souto-Carneiro MM, Mahadevan V, Takada K et al. (2009) Alterations in peripheral blood memory B cells in patients with active rheumatoid arthritis are dependent on the action of tumour necrosis factor. Arthritis Res Ther 11, R84.
International Journal of Rheumatic Diseases 2015; 18: 379–381
5 Moura RA, Weinmann P, Pereira PA et al. (2010) Alterations on peripheral blood B-cell subpopulations in very early arthritis patients. Rheumatology 49, 1082–92. 6 Samuels J, Ng Y-S, Coupillaud C et al. (2005) Impaired early B cell tolerance in patients with rheumatoid arthritis. JEM 201, 1659–67. 7 Olsen NJ, Callahan LF, Pincus T (1988) In vitro rheumatoid factor synthesis in patients taking second-line drugs for rheumatoid arthritis. Independent associations with disease activity. Arthritis Rheum 31, 1090–6. 8 Leandro MJ, Cambridge G, Ehrenstein ME et al. (2006) Reconstitution of peripheral blood B cells after depletion with rituximab in patients with rheumatoid arthritis. Arthritis Rheum 54, 613–20. 9 Nielen MMJ, van Schaardenburg D, Reesink HW et al. (2004) Specific autoantibodies precede the symptoms of rheumatoid arthritis: a study of serial measurements in blood donors. Arthritis Rheum 50, 380–6. 10 Thurlings RM, Wijbrandts CA, Mebius RE et al. (2008) Synovial lymphoid neogenesis does not define a specific clinical rheumatoid arthritis phenotype. Arthritis Rheum 58, 1582–9. 11 Beduleva L, Menshikov I, Stolyarova E et al. (2014) Rheumatoid factor in idiotypic regulation of autoimmunity. Int J Rheum Dis 18, 408–20. 12 Beduleva L, Menshikov I (2010) Role of idiotype-anti-idiotype interactions in the induction of collagen-induced arthritis in rats. Immunobiology 215, 963–70. 13 Jefferis R (1995) Rheumatoid factors, B cells and immunoglobulin genes. Br Med Bull 51, 312–31. 14 Amara K, Steen J, Murray F et al. (2013) Monoclonal IgG antibodies generated from joint-derived B cells of RA patients have a strong bias toward citrullinated autoantigen recognition. J Exp Med 210, 445–55.
381
