RESUMEN
CD40-ligand [CD 154] is expressed on activated CD4+T lymphocytes and is essential for the T cell-dependent activation of B lymphocytes. CD154 is also expressed at the activated platelet surface. The study aim to investigate the role of CD154 in ITP pediatric patients and correlate their levels with the course and progression of the disease. This study included 25 patients with acute ITP [13 females and 12 males] with age ranged between 2-6 years [group 1] and 25 patients with chronic ITP [14 females and II males] with an age ranging between 8-12 years [group II], also 25 apparently healthy children [10 females and 15 males] with an age ranging between 3-12 years as control [group III]. Studied groups were subjected to the following investigations; complete blood count, bone marrow examination and flowcytometric analysis of CD154 B lymphocyte counts. We found that there was a highly significant increase in CD 154 in patients with acute ITP compared with chronic ITP and control group [p=0.001 and 0.9001 respectively]. Also there was a negative correlation between CDI54 and platelet count in acute and chronic groups [r=-0.6, p=0.004 and r=-0.5, p=0.005 respectively]. There was a positive correlation between CD 154 and lymphocytic count in acute and chronic groups [r=0.422, p=0.007 and r=0.77, p=0.001 respectively]. In conclusion, the increased number of CD 154 might be one of the mechanisms that cause immune regulation dysfunction in ITP. Furthermore, the count is related to the severity of the disease as it was highly increased in acute phase than chronic and therefore CD154 expression is increased in ITP and is able to drive the activation of auto reactive B lymphocytes in this disease