This is huge! Why splenectomies may not work.

The severity of ITP and effectiveness of treatments vary from patient to patient. A new Canadian study shows why there is such variance in both. Platelet surfaces are covered with thousands of different proteins. Each type of antibody targets a specific protein on the platelet. When the first antibody finds a platelet it latches on and leads the platelet to an organ in the body where the platelet will be destroyed. Originally it was thought all ITP antibodies lead platelets to the spleen to be destroyed. Most previous treatments for ITP were to prevent antibodies from destroying platelets in the spleen.

Dr. Heyu Ni, researcher at the Keenan Research Centre for Biomedical Science of St. Michael’s Hospital, in Toronto, said some antibodies destroy platelets in the liver, not in the spleen. Research studies with mice found that antibodies targeting the GPIb (pronounced ‘G P 1 b’) protein lead to platelet destruction in the liver. However, antibodies targeting the GPIIbIIIa (pronounced ‘G P 2 b 3 a’) protein caused platelet destruction in the spleen. By detecting the specific antibodies in an ITP patient, doctors may be able to determine where and how the immune system will attack platelets. Dr. Ni said, “… because we now know the liver’s immune response destroys platelets that are covered with GPIb, we may be able to design new therapies to stop this type of destruction.” He said certain drugs, like Tamiflu, might be able to prevent the liver’s immune response to platelets. Additional tests with human blood samples showed Tamiflu may inhibit destruction of platelets with antibodies that target GPIb. Some ITP patients around the world have now been treated with Tamiflu for their ITP. However, more research is needed.

Heyu Ni, et al. “Desialylation is a mechanism of Fc-independent platelet clearance and a therapeutic target in immune thrombocytopenia.” Nature Communications 6, Article number: 7737 doi:10.1038/ncomms8737.

“Study in mice may identify new ways to treat immune thrombocytopenia.” Report provided by St. Michael’s Hospital, Toronto, Canada. July 17, 2015.
www.stmichaelshospital.com/media/detail.php?source=hospital_news/2015/20150717_hn

For anyone interested in more along this line of research, do this search on google scholar:
scholar.google.com/scholar?q=Desialylation+itp

It is good to know there are people this smart working on ITP.

I wonder if this mechanism of action in the liver helps explain low platelet counts in people with various forms of liver disease. As usual, more research is needed.

It's pretty much the same as doing the indium test but from the other direction.

Several years ago I read about these different types of antibodies and the writer there had concluded that different antibodies were susceptible to different treatments. That was interesting too.

Yes, it is and will be very valuable once they can get it figured out. No more going down a whole line-up!

I already new that for some people platelet destruction occurs in the liver and not the spleen. One thing that was new to me was the idea that platelet destruction in the liver is the result of different antibodies which respond to different treatments. I also had not read before that Tamiflu (oseltamivir) may be able to treat one specific form of ITP, such as here:

Successful treatment with oseltamivir phosphate in a patient with chronic immune thrombocytopenia positive for anti-GPIb/IX autoantibody
2015, Vol. 26, No. 5 , Pages 495-497 (doi:10.3109/09537104.2014.948838)
Linlin Shao, Yang Wu, Hai Zhou, Ping Qin, Heyu Ni, Jun Peng, and Ming Hou
informahealthcare.com/doi/abs/10.3109/09537104.2014.948838

Also, I did not know that different ITP antibodies had actually been identified.

This might be a silly question, but can hematologists easily tell what kind of antibodies you have? Can my hemo tell where my platelets are destroyed and what kind of ITP I have? This is so interesting! I know my ITP is not the typical ITP, since it's never gone below 30000 (that I know of) in the 7 months I've had it.

Hi, they can do a blood test for antibodies but they never do, not up until now anyway. I did have mine looked at for a study but they didn't tell me the result.

As for where the platelets are destroyed, in the UK and some other European countries the indium test can be done whereby they tag some platelets with indium and then scan several times over a few days to see where they go. If it shows the destruction is taking place in the liver then a splenectomy will be ruled out.

They also know now that there are two types of ITP, antibody mediated and T cell mediated. They think that each type may need different treatments but its still at the study stage really.