Immunoglobulin M antiplatelet autoantibodies from mice immunized with rat platelets induce thrombocytopenia and platelet function impairment

Abstract

Antiplatelet monoclonal autoantibodies (mAbs) were derived from CBA mice immunized with rat platelets. Two IgM antiplatelet mAbs were further analyzed. L1C43 mAb bound a 150-160 kDa antigen, recognized activated platelets better than resting ones and impaired platelet adhesion, but not clot retraction. L1H31 mAb recognized a ±95 kDa molecule, bound similarly activated and resting platelets and did not modify platelet adhesion, but inhibited clot retraction. Both mAbs induced in vivo thrombocytopenia most likely through phagocytosis of opsonized platelets. These autoreactive antibodies can thus induce both platelet destruction and impairment of their function. They are reflective of autoantibodies found in human patients and may serve for further analysis of antiplatelet autoantibody pathogenicity and mechanisms of autoimmune disease.

Involvement of Fcα/μ Receptor in IgM Anti-Platelet, but Not Anti–Red Blood Cell Autoantibody Pathogenicity in Mice

“…Notably, autoantibody injection and LDV infection had additive effects because the administration of L1C43 mAb to infected mice led to the development of a more severe thrombocytopenia compared with mice that received either the Ab alone or the virus alone (p , 0.0286 and p = 0.0286, respectively). Similar results were obtained with another IgM anti-platelet mAb (L1H31) recognizing a distinct epitope (data not shown), suggesting that LDV plays a role in the exacerbation of the pathogenicity of these autoantibodies, both of which induce thrombocytopenia most likely through phagocytosis of opsonized cells (10). In contrast, using 4C8 IgM, a representative anti-erythrocyte mAb that promotes anemia through a massive agglutination of RBCs in spleen and liver rather than through phagocytosis (13, 26), we found no disease enhancement postinfection (Fig.…”

“…These IgM autoantibodies induced in vivo thrombocytopenia through uptake of opsonized platelets (10). In contrast, IgM anti-erythrocyte autoantibodies generated from NZB mice (11) cause anemia through spleen accumulation of agglutinated erythrocytes rather than through erythrophagocytosis (12,13).…”

Recapitulation of posttransfusion purpura by cross-strain platelet immunization in mice

“…Early reports showed that intraperitoneal injection of mice with rat RBCs regularly led to production of antibodies that recognized both rat and mouse RBCs [27][28][29][30] and that immunization of mice with rat platelets induced platelet-specific autoantibodies and moderate thrombocytopenia. 31,32 We are aware of only 2 previous studies in which autoimmune thrombocytopenia appears to have developed following platelet immunization between members of the same species. In 1965, Baldini described occasional, severe, and prolonged thrombocytopenia in dogs following repeated platelet transfusions from other randomly selected animals and attributed this to induction of autoantibodies.…”

Antibody-Independent Thrombocytopenia in Lactate Dehydrogenase-Elevating Virus-Infected Mice

“…To determine whether LDV-induced thrombocytopenia in animals that did not receive antiplatelet antibodies also resulted from increased platelet phagocytosis, CBA mice were treated with 200 l clodronate-containing liposomes, prepared as described previously (9), prior to LDV inoculation. This treatment completely abrogated antibody-mediated platelet destruction in LDV-infected mice (9) and did not modify platelet counts in uninfected animals (2). As shown in Fig.…”