Twenty-six patients with delayed hemolytic transfusion reactions ( DHTR ) were investigated. The reaction of hemolysis often was concealed by other disorders that were usually associated with signs of hemolysis or blood loss. Coating of red cells was analyzed with regard to IgG and/or complement bound in vivo. Although many of the alloantibodies involved (K [8]; E [5]; Fya [2]; Fyb [2]; D [1]; c [1]; multiple [7]) are usually thought to be incapable of complement activation, a strongly positive direct antiglobulin test (DAT) due to C3d was found in all cases. On first examination after transfusion, C3d was present on circulating red cells in large amounts and remained discernible for weeks and even months. IgG on red cells was detected by the DAT in only 10 out of 26 cases. By means of a sensitive radioimmunoassay, IgG was demonstrated in 16 out of 17 cases, but usually in small quantities. Despite the low IgG concentrations, the causative alloantibodies could be eluted in 25 of 26 cases, and, as shown by sequential investigations, in six cases were recoverable from circulating red cells for over 100 days posttransfusion. Since the antiglobulin reactions due to anti-complement were usually strong, not of the "mixed-field" type, and in some cases remained detectable on circulating red cells for months, we conclude that complement is regularly activated in DHTR and binds not only to donated but probably also to autologous red cells.

The development of hemolytic erythrocyte alloantibodies and autoantibodies complicates transfusion therapy in thalassemia patients. These antibodies ultimately increase the need for blood and intensify transfusion complications. There is a scanty data on the frequency of RBC alloimmunization and autoimmunization in Egyptian β thalassemia patients as pretransfusion antibody screening is not routinely performed. We studied the frequency of alloimmunization and autoimmunization among 200 multiply transfused β thalassemia patients and investigated the factors that possibly affect antibody formation. Of the 200 patients in our study, 94 were males and 106 females, with the age range of 2–37 years. Alloantibodies were detected in 36 (18%) of the patients, while autoantibodies were detected in 33 (16.5%). The dominant alloantibodies were directed against Kell (33%) and Rh (24.4%) groups. Alloimmunization had a significant relationship with treatment duration and the frequency of transfusion (P = 0.007, 0.001, respectively). The presence of autoantibodies was significantly related to age (P = 0.001), total number of transfused units (P = 0.000) and splenectomy (P = 0.000). The high prevalence of alloimmunization in the study population disclosed the need for providing phenotypically matched cells for selective antigens especially for Kell and Rh subgroups to reduce risk of alloimmunization and increase the efficiency of blood transfusion.

The authors present circumstantial evidence for the involvement of reactive hemolysis, i.e., C3-independent binding of the cytolytic C5b-9 complement complex to bystander red cells (RBC), in a case of intravascular immune hemolysis. Fresh serum obtained from a 6-year-old patient during the hemolytic episode, but not obtained thereafter, induced C5b-9-dependent hemolysis of human RBCs but the indirect C3 antiglobulin test remained negative. Particles (presumably RBC ghosts) isolated from the patient's plasma anticoagulated with EDTA at the peak of hemolysis were coated with C5b-9 complexes, whereas the direct antiglobulin test was strongly positive for IgA, only weakly positive for IgG, and negative for C3. Moreover, neither the autoantibodies isolated by elution (IgG plus IgA), nor free serum autoantibodies (IgA alone) activated complement in vitro. Additionally, serum samples collected later during the 12-month period of observation contained normal levels of C3, C4, C8, and C9, but markedly reduced levels of C7. These serums all produced strong reactive lysis in agarose plates, but not in test tubes. These results appear compatible with the working hypothesis that the intravascular hemolytic episode in this patient might have arisen through a local initiation of complement activation with subsequent C3-independent binding of C5b-9 to and hemolysis of bystander RBCs.

Background: The clinical relevance of antibodies directed against members of the Gerbich (GE) family of antigens is not invariably clear. Given the scarcity of serologically compatible red blood cells (RBC), various methods may have to be applied to assess the safety of transfusing serologically incompatible RBC. Patient and Methods: The serum of a 57-year-old male Caucasian admitted to hospital for gastrectomy was found to contain a highly reactive anti-GE2 antibody (IgG₁). In addition to a monocyte monolayer assay, 50 ml of GE2-positive RBC were transfused, and blood samples were taken before and 1 and 24 h after transfusion for flow-cytometric determination of transfused cells. Results: Both tests showed no increased destruction of GE2-positive RBC. The transfusion of 4 units of GE2-positive RBC was well tolerated, and hemoglobin increased adequately. Conclusion: This case may extend the information available not only on antibodies directed against members of the GE family of antigens but also on methods to estimate the survival of transfused RBC.

From November 1994 to November 1997 we investigated 133 patients with alloantibodies directed against high-frequency red cell antigens (Ab-HFA). More than 90% of these antibodies were found in females. Interestingly, all carriers of anti-Lu ^b/8 and 7 of 13 persons with anti-Yt^a were pregnant women. The majority of the Ab-HFA (n = 69, 51.9%) belonged to the clinically insignificant high-titer low-avidity (HTLA) antibodies with anti-Ch^a as the leading specificity (n = 47, 33.8%). The remaining HTLA specificities were anti-Kn^a (n = 9), anti-Rg^a (n = 4), anti-JMH (n = 3), anti-Yk^a (n = 3), anti-Sd^a (n = 2), and anti-McC^a (n = 1). In 32 additional cases (24.1%), Ab-HFA of uncertain or low clinical significance were detected: anti Yt^a (n = 13), anti-Lu ^b/8 (n = 13), anti-Co^a (n = 3), anti-Ge (n = 2), one anti-AnWj.Thus, Ab-HFA of no or uncertain clinical significance achieved a proportion of roughly 75%. Clinically significant antibodies were demonstrable in 29 (22%) patients: anti-Vel (n = 14), anti-Lan (n = 5), anti-Kp^b (n = 3), anti-k (n = 2), anti-Jk³ (n = 2), anti-KL (n = 1), anti-Tj^a (n = 1), anti-Di^b (n = 1). Hemolytic transfusion reactions were noted in 6 cases (4.5%); 3 of them occurred with anti-Vel and 3 with anti-Lan. Mild hemolytic disease of the newborn was observed in one case of anti-k. Three cases remained unresolved (2%). Multiple additional red cell alloantibodies, i. e. anti-Rh, anti-K, anti-Fy and others, were present in 24 patients (18.1%) with Ab-HFA, predominantly associated with anti-Yt^a (57%) and anti-Ch^a . Most importantly, the serological reactions of Ab-HFA were weak, uniform and difficult to differentiate from nonspecific reactions. Careful serological testing with a large panel of rare test cells is necessary to distinguish the harmful from the harmless Ab-HFA.