Immune Markers in Pediatric ITP on Second Line Therapy

Antiplatelet factors in the plasma of ITP patients, specifically IgG, have been attributed to platelet destruction through phagocytosis or complement-mediated lysis. However, these antibodies are only present in 60-70% of ITP patients, suggesting that other mechanisms may be involved in platelet destruction. B lymphocytes play a critical role in immune responses through antibody production, antigen presentation to T cells, and cytokine secretion. CD4+ T helper cells play a crucial role in supporting B cell development into antibody-secreting plasma cells. Furthermore, evidence of auto reactive CD4+ T cells targeting platelet epitopes has been reported. It was found that there is clonal expansion of a particular subset of CD8+ T cells, known as terminally differentiated effector memory T cells (TEMRA cells), in refractory ITP. Furthermore, CD8+ T cells induce platelet activation and apoptosis in an antibody-independent mechanism for refractory thrombocytopenia that may be amenable to therapeutic targeting. IFN-γ is an important cytokine involved in host defence and immune regulation. It is primarily produced by T helper, cytotoxic T, and natural killer cells. Dysregulated secretion of IFN-γ has been implicated in the development of autoimmune disorders. Initial studies on ITP focused on the role of autoantibodies. Therefore, drug discovery efforts have focused on suppressing aberrant humoral immunity through B cell depletion, disruption of immunoreceptor, and inhibition of autoantibody activity. By comparing the marker expression in different treatment response groups, the investigator can potentially identify markers that may serve as predictive or prognostic indicators of treatment response. This information could be valuable for guiding treatment decisions and optimizing patient outcomes in pediatric ITP.