John Semple

Research Synopsis

My research is aimed at understanding the cellular and molecular immune mechanisms responsible for the generation of IgG antibodies and T cells that recognize platelet antigens.

These effector responses can lead to clinically significant adverse effects such as autoimmunity causing immune thrombocytopenia (ITP) and alloimmunity causing platelet transfusion refractoriness.

In ITP, we are interested in how platelet antigens are processed and presented by antigen-presenting cells to activate T lymphocytes.

In platelet refractoriness, we study the pro-inflammatory nature of platelets responsible for adverse reactions during platelet transfusions, particularly how platelet Toll-like receptor expression modulates innate immune mechanisms.

We also study the recipient immune mechanisms that cause Transfusion Related Acute Lung Injury (TRALI), a serious complication of transfusion.

We are also interested in understanding how therapies such as intravenous gammaglobulin (IVIg), Rituxan and Thrombopoietin-mimetics increase platelet counts in immune thrombocytopenic disorders.