Aspectos imunohematológicos dos pacientes com anemia falciforme e a influência da hemoglobina S na distribuição linfocitária

Abstract

Introduction: Sickle cell anemia (SCA) is a genetic disease responsible for the production of hemoglobin S (HbS) and has a wide variety of clinical presentations. One of the most widespread therapies is transfusion, which, while offering clinical benefit, is not free from complications such as alloimmunization. Chronic inflammation composes the pathophysiology of sickle cell disease and may be an additional factor for alloimmunization. Sickle cell trait (SCT) is considered a benign and asymptomatic condition, however some clinical complications have been described in these patients. The objectives of this study were: to identify the proportion of alloimmunization, erythrocyte antigen profile and related factors, to evaluate the relationship between alloimmunization and diagnosis by neonatal screening (NS) in patients with SCA, and to evaluate the lymphocyte distribution of patients with SCA and SCT. Methods: We reviewed the medical records of patients with SCA followed up at a specialized outpatient clinic linked to a University Hospital, in order to obtain clinical, laboratory and neonatal screening results. Transfusion data and pre-transfusion tests were obtained at the local hemocenter. Patients with SCA, SCT and individuals without any hemoglobinopathies were included in a sample cut for peripheral blood immunophenotyping with evaluation of B lymphocytes, T lymphocytes (CD4 and CD8) and NK cells. Results: The sample consisted of 270 patients with a transfusion rate of 66.5% and alloimmunization of 19.6%. Patients were negative for highly immunogenic antigens of the Rh / Kell system. Eleven types of antibodies were identified, with anti-E, anti-e, anti-C, anti-JKa, anti-Fya and anti-Kell being more prevalent. The presence of autoantibodies was higher in alloimmunized patients compared to non-alloimmunized patients. Alloimmunization was related to higher mean age, higher frequency of hydroxycarbamide use, greater number of transfusions, and higher values of Mean Corpuscular Volume (MCV). The alloimmunization rate among patients diagnosed by NS was similar to that of patients with the later diagnosis (p = 0.08). Patients with SCA had lower values of CD4 + T lymphocytes and larger total NK cells, CD56dim and CD56bright. SCT patients presented increased total and CD56bright NK cells. Conclusions: The proportion of alloimmunized patients found was 19.6%, related to the higher mean age, higher frequency of hydroxycarbamide use and higher rate of autoantibodies. The most frequent alloantibodies were those of the Rh / Kell system. NS was not protective for alloimmunization. There are differences in the distribution of lymphocytes related to the presence of HbS and suggest that changes in the inflammatory state occur in asymptomatic patients with SCT.