Abstract
CD28 null T helper (T(h)) cells are rare in healthy individuals, but they are increased in various inflammatory and immune-mediated diseases. In this study, we determined the size of the CD4(+)/CD28 null T lymphocyte compartment in the peripheral blood of 40 autoimmune hemolytic anemia (AIHA) patients (idiopathic and secondary) and 20 healthy control subjects, using tri-color flow cytometry. The frequency and absolute count of CD4(+)/CD28 null T helper (T(h)) cells was significantly higher in idiopathic AIHA patients, compared to healthy controls (p = 0.001 and 0.001, respectively) and to patients with secondary AIHA (p = 0.04 and 0.01, respectively). The percentage of CD4(+)/CD28 null T(h) cells was also negatively correlated to the hemoglobin (Hb) level (p = 0.03). These findings demonstrate, for the first time, the expansion of this phenotypically-defined population of T lymphocytes in patients with idiopathic AIHA and indicate that it likely plays an etiological role in the development of this disease. However, establishing the use of this marker for diagnosis or monitoring treatment of such patients needs further studies.