Immune thrombocytopenia: a review on the pathogenetic role of immune cells

ABSTRACT

Introduction

Immune thrombocytopenia [ITP] is a common bleeding disorder with an isolated platelet count of less than 100 × 10⁹/L.

Areas covered

Relevant literature from 2003 to 2022 was retrieved and reviewed from the Google Scholar search engine and PubMed database. Antibodies produced by autoreactive B lymphocytes and the phagocytic function of macrophages are considered the most critical factors in platelet destruction. Also, macrophages present the antigen to T lymphocytes and activate them. Follicular helper T-cells [TFH] play a role in stimulating, differentiating, and activating autoreactive B cells, while cluster of differentiation [CD]-8+ T plays a role in platelet destruction through apoptosis. The classical pathway of the complement system also causes platelet destruction. By inhibiting platelet production, low levels of thrombopoietin and an immune response against megakaryocytes in the bone marrow worsen thrombocytopenia.

Expert opinion

T-cell subset changes and an increase in activated autoreactive B cells, in addition to the function of components of the innate immune system [the complement system, dendritic cells, and natural killer cells], play a critical role in the pathogenesis of the ITP. Accurate detection of these changes may lead to developing new therapeutic strategies and identifying better prognostic/diagnostic factors.

KEYWORDS:

• Immune thrombocytopenia
• platelet
• B lymphocyte
• T lymphocyte
• CD antigens
• Fc gamma receptor
• macrophages

Article highlights

• NK cells increase in patients with severe and treatment-resistant ITP.

• The ability of DCs in ITP patients to regulate the expression and activity of IDO1 decreases.

• Low C4 levels predict disease severity and have prognostic value in ITP.

• In patients with ITP, the number of plasma cells producing Ab increases, and the levels of cytokines APRIL, BAFF, and BLyS (which play roles in B cell activation, survival, and maturation) are also increased.

• Among T cells, emphasis is placed on the role of Th1, Th22, Th17, TFH, and TCD8+ in the pathogenesis of ITP.

• The levels of platelet-derived proteins, including CXCL5, CCL5, and EGF, decrease markedly in ITP, which is consistent with the degree of thrombocytopenia.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This paper was not funded.