Primary immune thrombocytopenia (ITP) is a common condition characterized by a low peripheral platelet count (100000/L) caused by cell-mediated and humoral-mediated destruction of the platelet. Immunological tolerance to platelet antigens is lost in these patients. The main step in the pathogenesis includes the overactivation of T-cells, particularly T-helper cells, the release of various cytokines, and the interaction of autoantibodies with platelet surface antigens, which results in platelet destruction by the immune system in the spleen. The most common PLT antigens against which autoantibodies are directed are CD41 and CD61. These antigens are occupied by autoantibodies so there is decreased detection of these antigens on the surface of platelets. PD1 is an important negative stimulatory molecule of the immune system a member of the CD28/B7 family. ITP patients have considerably increased levels of PD-1 on CD4+Tcells in their peripheral blood than healthy people., indicating that the PD1 molecule plays an important role in illness etiology.

Background programmed death (PD-1) has an important role in inhibiting the immune system in immune thrombocytopenic purpura (ITP) by switching off auto-reactive T-cells. This work aims to assess the expression of (PD)-1 negative co-stimulatory molecule in patients with ITP and to detect its relation with platelet count. Patient and methods, forty patients were newly diagnosed as ITP 13 males and 27 females were included, their age ranged from 1 to 43 years and twenty-six healthy subjects 8 males and 18 females as control group their age ranged from 5 to 62 year. Expression of PD-1+ CD4+ T-cells by B.D FACS Calibur flow cytometry was performed in ITP patients and healthy subjects on peripheral blood samples, Mo Abs supplied by BD Bioscience, United States.

Background and study aim: COVID-19 is a highly contagious viral infection that was initially discovered in late 2019 in China. Vitamin D was proposed as a COVID-19 severity indicator by many authors.However, the role of hypocalcemia has not yet been well established. So we evaluated serum levels of vitamin D and total calcium in adult patients infected with COVID-19 and correlated vitamin D and calcium levels with the severity and prognosis of the COVID-19 infection. Patients and Methods:Our study evaluated 98 patients (50 females, 48 males) who were diagnosed with positive SARS-CoV-2 polymerase chain reaction. The patients were categorized into severe and non-severe COVID-19 based on the Egyptian protocol for the management of COVID-19 patients. Serum vitamin D and calcium levels were estimated in all patients. Results:In severe COVID-19 individuals, serum vitamin D levels were significantly lower (P = 0.04). However, there was no statistically significant change in serum calcium levels between severe and non-severe COVID-19 patients (P = 0.7) despite the high prevalence of hypocalcemia in our cohort (88%, 86/98). There was no statistically significant difference in the blood levels of both vitamin D and calcium between the improved group of patients and the death group (P = 0.5, 0.1 respectively). Conclusion:Vitamin D deficiency is a risk factor for disease progression and severity in COVID-19 patients. Hypocalcemia is not linked to COVID-19 severity despite its high prevalence in these patients. However, to back up these findings, more research with bigger sample size is required .