Erythrocyte autoimmune disorder: red cell antibodies and the human allogeneic rosette test.
A new test termed the human allogeneic rosette test (HART) is reported for the detection of small amounts of erythrocyte autoantibodies. It compares the percentage of rosettes formed around lymphocytes from normal subjects when either red cells from patients are added or autologous or allogeneic normal red cells. The HART is positive when the percentage of rosettes made with the control's red blood cells is significantly more than the percentage of those made with the patient's red blood cells. Twenty-two out of twenty-six patients with a positive antiglobulin test had a positive HART. Thirty patients with a negative antiglobulin test but with clinical or biological data suggesting an erythrocyte autoimmune disorder were also studied with the HART. Out of sixteen patients with chronic lymphatic leukaemia, ten had a positive test; all three patients with idiopathic thrombocytopenic purpura showed a positive HART; two out of three patients with cirrhosis and one out of four patients with Hodgkin's disease also had a positive test. No correlation was found between the positivity of the HART in these patients and their haematological values. Two patients with suspected autoimmune haemolytic anaemia and with a negative anti-globulin test but a positive HART were treated with steroids. Both responded very rapidly to the treatment suggesting an immune origin for the anaemia. The HART has been reproduced experimentally. Normal human red blood cells, sensitized with different amounts of either an auto-antibody or anti-D were rosetted with autologous normal lymphocytes. The results showed that the percentage of rosettes with red cells coated with small amounts of antibody was significantly less than the percentage of rosettes with uncoated red cells. A plot of these results seemed to indicate that the HART was about twenty times more sensitive than the antiglobulin test. The nature of the cells involved in the positive HART-negative direct antiglobulin test red cell binding was also analysed. They appear to be related to the T cell population. The role of the receptors for IgG in the HART was demonstrated by showing that aggregated and non-aggregated human IgG could inhibit the HART phenomenon. In conclusion, the HART appears to be a new and sensitive immunological test capable of analysing erythrocyte autoimmune disorders.