T Lymphocyte Study in Sickle Cell Anaemia by Means of Rosetting Techniques

P. Hernández, C. Cruz, Instituto de Hematología e Inmunología, La Habana (Cuba) The status of cell-mediated immunity in sickle cell anaemia (SCA) is currently not completely clear, and reported studies are few. T lymphocyte populations have been found decreased [2, 3] or normal [4, 8]. We would like to add our recent studies performed by means of rosetting techniques [4, 7, 11] in 25 SCA patients (10 males, 15 females, mean age 20 years, range 16–29 years). All patients were in a steady state. Rosettes that were formed immediately after centrifuga-tion of a mixture of sheep red blood cells and lymphocytes, and which evidence lymphocytes possessing a high affinity for sheep red blood cells, have been termed ‘active’ E rosettes; the rosettes that required incubation at 4°C for optimal formation were designated as total E rosettes [11]. Statistical comparisons between groups were done using the Student t test. The white blood cell (WBC) total count, percentage, and absolute number of lymphocytes and rosetting T lymphocytes are shown in table I. The WBC were significantly elevated in SCA patients compared to normal controls. Although no difference was found between both groups in mean lymphocyte percentage, a significant increase was observed in SCA patients when these cells were expressed as absolute number. Total E rosette and active E rosette percentages were significantly decreased in the SCA group. Active E rosette percentage has also been observed decreased in a group of children with SCA [5]. Autologous and al-logeneic rosette percentages were not different from control values. When expressed as absolute numbers, all types of rosetteforming cells were significantly increased in the SCA group. Both active and autologous rosettes detect T lymphocyte subpopulations which are not yet completely identified in their functions. Both clinical and experimental studies suggest that the active rosette-forming cells represent a subpopulation of peripheral T lymTable I. Immunological data in SCA (mean ± SD)