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Warm reactive autoantibodies are encountered relatively frequently in tertiary care hospitals. We studied 100 consecutive patients with warm autoantibodies to correlate their clinical and serologic features. Study patients (56 male, 44 female) had various diagnoses and a mean age of 53.5 years (range, 3-90 years). Autoimmune hemolysis was documented in 29 patients; 20 patients (69%) in this subset had diseases classically associated with warm autoimmune hemolytic anemia (hematologic and autoimmune disorders). All study patients demonstrated IgG on their RBCs (direct antiglobulin test [DAT] reactivity range, microscopic to 4+); 49 also demonstrated C3 (reactivity range, microscopic to 3+). The DAT for IgG was 2+ or more in 25 (86%) of 29 patients with hemolysis; the DAT for IgG was 1+ or less in 45 (63%) of 71 patients without hemolysis. In patients with hemolysis, 21 (72%) of 29 had a DAT reactive for C3. These findings may be useful in determining the clinical significance of warm autoantibodies and the extent to which patients should be followed up for hemolysis.

Anti-Jra can be clinically significant as demonstrated by acute hemolysis in the second case. The MMA accurately predicted the clinical outcome of each case and appears to be a useful tool in predicting the biologic behavior of anti-Jra.

The significance of warm-reactive autoantibodies in pediatric patients has not been a subject of thorough evaluation. This study was undertaken to correlate the clinical and serologic features of these antibodies to identify predictors of clinical significance. Forty-two consecutive patients with serologically detectable warm-reactive autoantibodies were studied. These patients (21 male, 21 female) had a mean age of 9 years (range: 2 mo to 21 y). Primary diagnoses included autoimmune disorders (14), sickle cell disease (14), viral infection (4), idiopathic autoimmune hemolytic anemia (2), leukemia (2), and other diseases (6). Autoimmune hemolysis, as determined by clinical and laboratory findings, was documented in 24 patients (57%). Serologic studies revealed that all patients demonstrated IgG on their red cells [Direct Antiglobulin Test (DAT) reactivity range: microscopic to 3+]; 17 (40%) also demonstrated complement (DAT reactivity range: microscopic to 2+). There was a correlation between the strength of the DAT for IgG and the presence of complement on the red cells, with both being important predictors of hemolysis. These findings may be useful in predicting the clinical significance of warm-reactive autoantibodies in pediatric patients and allow for more efficient and effective follow-up care.

Envenomation by the brown recluse spider (loxoscelism) is classically associated with a necrotic ulcer. Systemic manifestations occur in a minority of cases, but are generally mild and self-limited. The hematologic complications of brown recluse spider bite range from mild hemolysis to fulminant intravascular hemolysis with or without evidence of disseminated intravascular coagulation. Intravascular hemolysis is a rare but occasionally lethal complication of brown recluse spider envenomation. This article presents two cases of severe hemolysis associated with loxoscelism occurring in two young women in Memphis, Tennessee. The second documented death in an adult from severe hemolysis due to a brown recluse spider bite is reported. A review of the literature emphasizing the pathogenic mechanisms of spider bite hemolysis is also included.

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Whole blood, when compared with component therapy, is associated with fewer donor exposures yet provided equally effective replacement therapy for blood loss in liver transplantation patients.

IntroductionThe red blood cell (RBC) membrane is architecturally complex and is characterized by significant biochemical diversity. Protein-, lipoprotein-, glycoprotein-, and carbohydrate-rich structures play an important role in ensuring the physical integrity of the cell and carrying out its physiologic functions. 1 However, the presence of these diverse RBC-surface molecules can also have adverse consequences. Several of these structures carry defined polymorphic epitopes, recognized serologically as blood group antigens, which can stimulate alloimmune responses (alloimmunization) after red blood cell transfusion or pregnancy. A second exposure to the same antigen may lead to serious clinical consequences, including hemolytic transfusion reactions and hemolytic disease of the newborn. Alloimmunization is particularly problematic in patient groups who receive multiple transfusions. For example, up to 30% of chronically transfused patients with sickle cell disease become sensitized to one or more blood group antigens. 2 Aside from alloimmunization, a more recently recognized consequence of the presence of diverse molecules on the surface of RBCs is that microorganisms have adapted to use certain ones as "docking points" in the initiation of disease. As an example, parvovirus B19 (a prominent cause of pure red cell aplasia) homes to erythroid precursors in the marrow through an interaction with the P blood group antigen. 3 In addition, the Duffy and glycophorin A blood group glycoproteins have been shown to play important roles as receptors for human malaria parasites. 4 Plasmodium vivax has an absolute requirement for a Duffy protein interaction in order to successfully invade and parasitize human RBCs. Consequently, red cells of the Fy aϪbϪ phenotype are resistant to invasion. 5 Plasmodium falciparum malaria parasites use glycophorin A epitopes to achieve the efficient invasion of RBCs. 6 The essential biochemistry of the complex invasion process of this parasite is not as well understood as that for P vivax. However, the gene encoding an important glycophorin A binding ligand of P falciparum, EBA-175, has been cloned and is being intensively studied. [7][8][9] There are circumstances in which it would be desirable to remove some of the antigenic epitopes or potential binding sites from the RBC surface, either to prevent alloimmunization or make RBCs resistant to microbial attack. Enzymatic removal of specific protein or carbohydrate structures is one possible approach. By using a specific exoglycosidase, this technique has been used successfully to cleave the B blood group antigen, allowing for the conversion of group B RBCs to group O before transfusion. 10,11 However, this general approach is limited by the availability of enzymes of the required specificities. Of the more than 200 known blood group antigens, B is the only antigen that has been specifically and effectively removed enzymatically. Although other less-specific proteases and glycosidases will certainly remove many antigens, they will also compr...