PF4/heparin complexes are T cell–dependent antigens

Suvarna, Shayela; Rauova, Lubica; McCracken, Emily; Goss, Christina M.; Sachais, Bruce S.; McKenzie, Steven E.; Reilly, Michael P.; Gunn, Michael D.; Cines, Douglas B.; Poncz, Mortimer; Arepally, Gowthami M.

doi:10.1182/blood-2004-12-4955

Cited by 44 publications

(50 citation statements)

References 24 publications

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“…The specificity of the assay has been confirmed by experiments showing that the antibodies display greater binding to murine PF4 (mPF4)/heparin than to mPF4 alone and that antibody binding is inhibited by an excess amount of heparin. 32 In addition, our studies have demonstrated that wild-type mice injected with mPF4/heparin complexes, but not mPF4 alone or heparin alone, develop marked levels of anti-mPF4/heparin antibodies. 30,32 T-cell-dependent and T-cell-independent antigen immunizations T-cell-dependent and T-cell-independent antigen immunizations were performed as described previously.…”

Section: Pf4/heparin Immunizationmentioning

confidence: 63%

“…32 In addition, our studies have demonstrated that wild-type mice injected with mPF4/heparin complexes, but not mPF4 alone or heparin alone, develop marked levels of anti-mPF4/heparin antibodies. 30,32 T-cell-dependent and T-cell-independent antigen immunizations T-cell-dependent and T-cell-independent antigen immunizations were performed as described previously. 33 Briefly, 8-to 10-week-old mice were immunized intraperitoneally with 100 mg of the T-cell-dependent antigen nitrophenyl-chicken g globulin (NP-CGG; Sigma-Aldrich) mixed 1:1 with Alum adjuvant (Pierce) (200 mL/mouse) or 50 mg of the T-cell-independent antigen trinitrophenyl-Ficoll (TNP-Ficoll; Sigma-Aldrich) mixed 1:1 with Alum adjuvant (200 mL/mouse).…”

Section: Pf4/heparin Immunizationmentioning

confidence: 63%

“…30,31 Importantly, mouse anti-PF4/ heparin antibodies share important serologic and functional characteristics with human HIT antibodies, including IgG isotypes, production kinetics, binding to mouse PF4/heparin complexes but not PF4 or heparin alone, and the ability to activate platelets in the presence of low-dose heparin. 32 Here, we use this mouse model in combination with Notch2-deficient mice and adoptive transfer of B-cell subsets to dissect the immune response to PF4/heparin. We show that MZ B cells are critical for PF4/heparin-specific antibody production.…”

Section: Introductionmentioning

confidence: 99%

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Critical role for mouse marginal zone B cells in PF4/heparin antibody production

Zheng

Podd

et al. 2013

Blood

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Heparin-induced thrombocytopenia (HIT) is an immune-mediated disorder that can cause fatal arterial or venous thrombosis/thromboembolism. Immune complexes consisting of platelet factor 4 (PF4), heparin, and PF4/heparin-reactive antibodies are central to the pathogenesis of HIT. However, the B-cell origin of HIT antibody production is not known. Here, we show that anti-PF4/heparin antibodies are readily generated in wild-type mice on challenge with PF4/heparin complexes, and that antibody production is severely impaired in B-cell-specific Notch2-deficient mice that lack marginal zone (MZ) B cells. As expected, Notch2-deficient mice responded normally to challenge with T-cell-dependent antigen nitrophenyl-chicken g globulin but not to the T-cell-independent antigen trinitrophenylFicoll. In addition, wild-type, but not Notch2-deficient, B cells plus B-cell-depleted wild-type splenocytes adoptively transferred into B-cell-deficient mMT mice responded to PF4/heparin complex challenge. PF4/heparin-specific antibodies produced by wild-type mice were IgG2b and IgG3 isotypes. An in vitro class-switching assay showed that MZ B cells were capable of producing antibodies of IgG2b and IgG3 isotypes. Lastly, MZ, but not follicular, B cells adoptively transferred into B-cell-deficient mMT mice responded to PF4/heparin complex challenge by producing PF4/heparin-specific antibodies of IgG2b and IgG3 isotypes. Taken together, these data demonstrate that MZ B cells are critical for PF4/heparin-specific antibody production. (Blood. 2013;121(17):3484-3492)

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Section: Pf4/heparin Immunizationmentioning

confidence: 63%

Section: Pf4/heparin Immunizationmentioning

confidence: 63%

Section: Introductionmentioning

confidence: 99%

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Critical role for mouse marginal zone B cells in PF4/heparin antibody production

Zheng

Podd

et al. 2013

Blood

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“…[10][11][12]17 A previous study reported that athymic nude mice fail to response to PF4/heparin challenge, indicating the involvement of T cells in HIT antibody production. 18 However, athymic nude mice possess many immune defects, including impaired development of B cells. 19 Thus, inability of these mice to produce PF4/heparin-specific antibodies could be due to something other than T-cell deficiency per se, including defective B cells.…”

Section: Resultsmentioning

confidence: 99%

Critical role of CD4 T cells in PF4/heparin antibody production in mice

Zheng

Padmanabhan

et al. 2015

Blood

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Antibodies specific for platelet factor 4 (PF4)/heparin complexes are central to the pathogenesis of heparin-induced thrombocytopenia. Marginal zone B cells appear to be the source of such antibodies, but whether T-cell help is required is unclear. Here, we showed that induction of PF4/heparin-specific antibodies by PF4/heparin complexes was markedly impaired in mice depleted of CD4 T cells by anti-CD4 antibodies. Furthermore, Rag1-deficient recipient mice produced PF4/heparin-specific antibodies upon PF4/heparin challenge when reconstituted with a mixture of wild-type splenic B cells and splenocytes from B-cell-deficient (mMT) mice but not splenocytes from T-and B-cell-deficient (Rag1 knockout) mice. Lastly, mice with B cells lacking CD40, a B-cell costimulatory molecule that helps T-cell-dependent B-cell responses, displayed a marked reduction of PF4/ heparin-specific antibody production following PF4/heparin challenge. Together, these findings show that helper T cells play a critical role in production of PF4/heparin-specific antibodies. (Blood. 2015;125(11):1826-1829 Introduction Heparin-induced thrombocytopenia (HIT) is the most common druginduced, antibody-mediated thrombocytopenia and occurs 3 to 6 days following heparin treatment.1,2 HIT patients develop antibodies quickly, however, which are typically undetectable in a few months. Platelet factor 4 (PF4)/heparin-specific antibodies, central to the pathogenesis of HIT, are predominantly of the immunoglobulin G1 (IgG1) isotype with some IgG2 in humans.2-4 IgG/PF4/heparin immune complexes bind FcgRIIA on the platelet surface and induce platelet activation, leading to thrombocytopenia and a high risk of arterial and/or venous thrombosis/thromboembolism. 5,6 Long-lived mature B cells comprise 3 subsets: marginal zone (MZ), B1, and follicular B cells. 7,8 The MZ subset has been shown to be critical for production of PF4/heparin-specific antibodies.9 Typically, MZ B cells produce IgM or IgG antibodies independent of T-cell help. [10][11][12] Indeed, HIT patients have features of a T-cell-independent humoral immune response, characterized by rapid onset and decline of antibodies and apparent absence of immunologic memory.1 However, patients with severe HIT possess T cells that have a T-cell receptor with highly restricted complementarity determining region 3 regions and are responsive to PF4/heparin, suggesting a role of T cells in HIT pathogenesis. 13,14 Nonetheless, direct evidence for a role of T cells in HIT pathogenesis has not been reported. Here, we describe studies to define the role of T-cell help in regulating production of PF4/heparin-specific antibodies. Study design MiceEight-to 10-week-old Rag1-deficient, CD40-deficient, mMT, and wild-type C57BL/6 mice from The Jackson Laboratory were maintained in the Biological Resource Center at the Medical College of Wisconsin (MCW). Animal protocols were approved by the MCW Institutional Animal Care and Use Committee. In vivo depletion of CD4 T cellsWild-type C57BL/6 mice were injected intraperitoneally with ...

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“…The role of T cells in the HIT immune response remains uncertain in this context, although it was supported by a study based on a murine immunization model. 4 As illustrated in their article (see figure), Krauel et al also deduced from their experiments that antibodies specific to modified PF4 and synthesized in infected patients could contribute to host defenses by allowing the binding of PF4-coated bacteria to granulocytes and their subsequent phagocytosis. Their findings thus support the concept that PF4 has a significant role in bacterial defense.…”

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confidence: 96%