Immune thrombocytopenia (ITP) is an autoimmune disorder, mediated mainly by autoantibodies against platelet glycoprotein GPIIbIIIa and GPIbα resulting in enhanced platelet destruction. Decreased platelet production and cellular immunity also contribute to ITP. GPIIbIIIa and GPIbα are distinct platelet receptors. Previous studies suggested that anti-GPIbα (versus anti-GPIIbIIIa)-mediated ITP is less responsive to IVIG therapy. However, little information is available whether antibody specificities also dictate efficacy of Glucocorticosteroids (GC), which are the first-line ITP treatment. Here, I first induced ITP in mice by passive administration of anti-GPIbα or anti-GPIIbIIIa antibodies. Results suggest GCs were more effective at amelioration of anti-GPIIbIIIa-mediated thrombocytopenia. I repeated this observation in an active ITP model, in which splenocytes from wild-type platelet immunized GPIbα-/- or GPIIIa-/- mice were engrafted into wild-type mice, which developed ITP. Thus, I established new murine models of ITP for GC therapy and demonstrated that anti-GPIbα-mediated thrombocytopenia may be less responsive to GC therapy.

Immune thrombocytopenia (ITP) is an autoimmune disorder, mediated mainly by autoantibodies against platelet glycoprotein GPIIbIIIa and GPIbα resulting in enhanced platelet destruction. Decreased platelet production and cellular immunity also contribute to ITP. GPIIbIIIa and GPIbα are distinct platelet receptors. Previous studies suggested that anti-GPIbα (versus anti-GPIIbIIIa)-mediated ITP is less responsive to IVIG therapy. However, little information is available whether antibody specificities also dictate efficacy of Glucocorticosteroids (GC), which are the first-line ITP treatment. Here, I first induced ITP in mice by passive administration of anti-GPIbα or anti-GPIIbIIIa antibodies. Results suggest GCs were more effective at amelioration of anti-GPIIbIIIa-mediated thrombocytopenia. I repeated this observation in an active ITP model, in which splenocytes from wild-type platelet immunized GPIbα-/- or GPIIIa-/- mice were engrafted into wild-type mice, which developed ITP. Thus, I established new murine models of ITP for GC therapy and demonstrated that anti-GPIbα-mediated thrombocytopenia may be less responsive to GC therapy.

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