The severity of immune thrombocytopenia (ITP) is inversely associated with serum levels of C3 and C4 in both subtypes, according to a new literature review published in the journal Immunological Medicine

Moreover, the study showed that a variety of complement abnormalities in complement regulatory proteins, initial proteins, and end products were reported in primary ITP, while abnormalities were limited to the initial proteins in connective tissue diseases-related ITP.

Read more about the different types of ITP

In both primary and secondary ITP, there was activation of the early complement system, primarily through the activation of C3 and C4. In primary ITP, a more extensive complement activation was seen, the authors said.

“Based on the results presented herein, it can be assumed that there are patients (mainly refractory cases) for whom complement therapy is effective and that analysis of the complement system is important for stratifying patients,” the researchers concluded.

Recent work has shown that ITP is associated with complement abnormalities, the study team noted. 

The aim of the present study was to identify the characteristics of these abnormalities. 

The results presented are based on the work of a team of researchers, led by Kunihiro Yamaoka, MD, PhD, at the Kitasato University School of Medicine in Sagamihara, Japan, who conducted a literature review of all the articles about ITP and complement abnormalities.

The team identified and analyzed 17 articles, of which 8 were about primary ITP and 9 were about ITP related to connective tissue disorders.

ITP is a rare bleeding disorder characterized by an unusually low (usually less than 100,000/µL) platelet count caused by the production of autoantibodies mistakenly targeting glycoprotein 2b/3a complex, 1b/2a, or 6 found on the platelet membrane leading to increased removal of platelets in the spleen by splenic macrophages and decreased platelet production.


Shindo R, Abe R, Oku K, et al. Involvement of the complement system in immune thrombocytopenia: review of the literature. Immunol Med. Published online May 26, 2023. doi:10.1080/25785826.2023.2213976