John W. Semple
Encyclopedia
John W. Semple is a Canadian Scientist at St. Michael's Hospital
and a Professor of Pharmacology at the University of Toronto
. He was born in Windsor, Ontario
in 1959 and received his PhD in Immunology at Queen's University
at Kingston, Ontario
. In 1991, Semple, along with John Freedman, discovered a T helper cell
defect in patients with the bleeding disorder called immune thrombocytopenic purpura
(ITP). ITP is the condition of having a low platelet
count (thrombocytopenia) and most causes appear to be related to antibodies 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
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.
St. Michael's Hospital (Toronto)
St. Michael's Hospital is a teaching hospital and medical centre in Downtown Toronto, Ontario, Canada. It was established by the Sisters of St. Joseph in 1892, with the founding goal of taking care of the sick and poor of Toronto's inner city. The hospital provides tertiary and quaternary services...
and a Professor of Pharmacology at the University of Toronto
University of Toronto
The University of Toronto is a public research university in Toronto, Ontario, Canada, situated on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution of higher learning in Upper Canada...
. He was born in Windsor, Ontario
Windsor, Ontario
Windsor is the southernmost city in Canada and is located in Southwestern Ontario at the western end of the heavily populated Quebec City – Windsor Corridor. It is within Essex County, Ontario, although administratively separated from the county government. Separated by the Detroit River, Windsor...
in 1959 and received his PhD in Immunology at Queen's University
Queen's University
Queen's University, , is a public research university located in Kingston, Ontario, Canada. Founded on 16 October 1841, the university pre-dates the founding of Canada by 26 years. Queen's holds more more than of land throughout Ontario as well as Herstmonceux Castle in East Sussex, England...
at Kingston, Ontario
Kingston, Ontario
Kingston, Ontario is a Canadian city located in Eastern Ontario where the St. Lawrence River flows out of Lake Ontario. Originally a First Nations settlement called "Katarowki," , growing European exploration in the 17th Century made it an important trading post...
. In 1991, Semple, along with John Freedman, discovered a T helper cell
T helper cell
T helper cells are a sub-group of lymphocytes, a type of white blood cell, that play an important role in the immune system, particularly in the adaptive immune system. These cells have no cytotoxic or phagocytic activity; they cannot kill infected host cells or pathogens. Rather, they help other...
defect in patients with the bleeding disorder called immune thrombocytopenic purpura
Purpura
Purpura is the appearance of red or purple discolorations on the skin that do not blanch on applying pressure. They are caused by bleeding underneath the skin...
(ITP). ITP is the condition of having a low platelet
Platelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days...
count (thrombocytopenia) and most causes appear to be related to antibodies 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
Cytokine
Cytokines are small cell-signaling protein molecules that are secreted by the glial cells of the nervous system and by numerous cells of the immune system and are a category of signaling molecules used extensively in intercellular communication...
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.