Sandi, those are very important questions.
It should be obvious I have no info on the antibodies a user may have. Folks rarely report that. So yes, the antibody associations are based on conclusions made in studies, reasonable deductions, and a process of elimination - based on the theory that only 4 antibodies account for all ITP cases as described
Let me do this as it came to me, and start with type 2. See
and the study referenced. There you can see that the GPIb-IX antibody (type 2) is associated with poor steroid and IVIG responses. This is because of 'desialylation' process which occurs in the liver. IVIG doesn't affect the liver, it affects processes in the spleen, which explains the poor IVIG response. Also, I've read in an old study that good IVIG response predicts splenectomy possible success. This is corroborating evidence to the liver / IVIG connection.
Next was type 1. Unfortunately I have lost reference to the pertinent study - can't find it again. Blah. Basically it said something along the lines that ITP'ers with GPIIb-IIIa antibodies were typically associated with a good steroid response.
For TPO antibodies, type 3, no studies were used. I think it is reasonable to deduce it though. The logic is suggested in
. The basics of the idea is that folks with TPO antibodies have a stronger Promacta response than other ITP types. This is because increased platelet production (due to Promacta) does not cause the immune system to ramp up antibody production - as it does in GPIIb-IIIa (type 1) response. In type 1, platelet increases cause a ramping up of the immune system, which causes a higher and higher Promacta dose, until eventually the immune system response is overcome and counts rise substantially. In type 3, immune system destruction of TPO is independent of platelet count and so an immune response doesn't have to be overcome. Finally, it is noted that ITP'ers with a strong Promacta response also have a strong IVIG response and a poor steroid response. So the type 3 steroid and IVIG response is backed into from actuarial Promacta response.
For type 4, TPO (cMpl) receptor antibodies, again, deductions were made. The idea was first suggested
. The idea is that TPO receptors do not circulate through the blood stream and never make it to the spleen - as glycoprotein and TPO antibodies do. The spleen is where IVIG retards antibody responses so there shouldn't be any sort of substantive response similar to the glycoprotein and TPO antibodies responses to IVIG. Because of this dynamic, and a process of elimination, the unique and odd 'weak' IVIG response characteristic of some ITP'ers is assigned to type 4.
Roomer has it there will be
for the newly discovered antibodies soon - once it gets out of 'research' stage.
The usefulness of the study isn't really about antibodies. That column in the table can be ignored if desired. LOL, still I have answered your question, which makes for good documentation. The useful information is that steroid response X, and IVIG response Y, leads to a tailored response plan Z. Cheers to Probiotics !