John W. Semple is a Canadian Scientist formally at St. Michael's Hospital and a Professor of Pharmacology at the

University of Toronto The University of Toronto (UToronto or U of T) is a public research university in Toronto, Ontario, Canada, located on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution ...

. He is currently a Professor of Transfusion Medicine at Lund University in Sweden. He was born in

Windsor, Ontario Windsor is a city in southwestern Ontario, Canada, on the south bank of the Detroit River directly across from Detroit, Michigan, United States. Geographically located within but administratively independent of Essex County, it is the souther ...

in 1959 and received his PhD in Immunology at

Queen's University Queen's or Queens University may refer to: *Queen's University at Kingston, Ontario, Canada *Queen's University Belfast, Northern Ireland, UK **Queen's University of Belfast (UK Parliament constituency) (1918–1950) **Queen's University of Belfast ...

Kingston, Ontario Kingston is a city in Ontario, Canada. It is located on the north-eastern end of Lake Ontario, at the beginning of the St. Lawrence River and at the mouth of the Cataraqui River (south end of the Rideau Canal). The city is midway between Toro ...

. In 1991, Semple, along with John Freedman, discovered a

T helper cell The T helper cells (Th cells), also known as CD4+ cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines. They are considere ...

defect in patients with the bleeding disorder called immune thrombocytopenia (ITP). ITP is a condition of having a low platelet count (thrombocytopenia) and most causes appear to be related to

antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...

and T cells against platelets. Very low platelet counts can lead to a bleeding diathesis and purpura. The T cell defect was initially shown to be an exaggerated interleukin-2 response when T cells were cultured with platelets in vitro. Subsequently, this

cytokine Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...

abnormality was shown by others to be responsible for many of the autoimmune mechanisms causing the disorder.). The importance of understanding the T cell defects in ITP is that novel therapies aimed at these cells may significantly benefit patients with ITP.

References

External links

John Semple's laboratory homepage

John Semple's biography at St. Michael's Hospital

1959 births Canadian medical researchers Canadian immunologists Living people Medical educators Queen's University at Kingston alumni People from Windsor, Ontario Scientists from Toronto Academic staff of the University of Toronto 20th-century Canadian scientists 21st-century Canadian scientists {{Canada-med-bio-stub