Immunohematology最新文献

Variant RHCE alleles are found mainly in Afro-descendant individuals, as well as in patients with sickle cell disease (SCD). The most common variants are related to the RHCE*ce allele, which can generate partial e and c antigens. Although RHCE variant alleles have been extensively studied, defining their clinical significance is a difficult task. We evaluated the risk of RhCE alloimmunization as a consequence of partial antigens in patients with a positive phenotype transfused with red blood cell (RBC) units with the corresponding antigen. A retrospective study was performed with Brazilian patients, evaluating the number of antigen-positive transfused RBC units (incompatible due to partial antigen) in 27 patients with SCD carrying RHCE variant alleles who did not develop antibodies as well as evaluating the variants present in 12 patients with partial phenotype and correlated antibody (one patient with SCD and 11 patients with other pathologies). Two patients showed variant alleles with molecular changes that had not yet been described. Variant RHCE alleles were identified in a previous study using molecular methods. RHCE*ceVS.01 was the most frequent allele found among the patients without antibodies. Six patients with partial c antigen had a mean of 3.8 c+ RBC units transfused, and 10 patients with partial e antigen were exposed for a mean of 7.2 e+ RBC units. Among the variant alleles found in alloimmunized patients, the most frequent was RHCE*ceAR, which was found in five patients; the antibodies developed were anti-hr^S and/or anti-c. Our results showed that RHCE*ceVS.01 is indeed the most frequent variant allele in our cohort of patients with SCD, but the partial antigens that were identified have low risk of alloimmunization. RHCE*ceAR is the most impactful variant in the Brazilian population with high risk of alloimmunization and clinically significant anti-hr^S formation.

The MAM blood group system (International Society of Blood Transfusion [ISBT] 041) consists of one high-prevalence antigen to date, first detected in a 31-year-old woman during her third pregnancy. Epithelial membrane protein 3 (EMP3) was recently identified as the gene coding the MAM antigen. Six unique genetic variants have been described in EMP3 in 11 MAM- individuals. EMP3 is an 18-kDa glycoprotein with a large extracellular domain containing at least one N-glycosylation site. The normal function of EMP3 is still unclear, but ex vivo culture of erythropoietic progenitor cells from MAM- individuals shows an increased yield of reticulocytes, suggesting that EMP3 acts as a brake during normal erythropoiesis. EMP3 is abundant on different cell types, including many epithelial tissues and blood cells. Interestingly, EMP3 expression has been suggested as a prognostic marker for a number of cancer types, both for good and poor prognoses. EMP3 may act as a tumor suppressor or an oncogene in different cancer contexts. The protein appears to interact with other cell surface receptors and affects the downstream signaling and function of these proteins. MAM- red blood cells express low levels of CD44 and, consequently, the antigens of the Indian blood group system are only weakly expressed. Clinically, the MAM blood group antigen is important with regard to blood transfusion and pregnancy. Anti-MAM can cause severe hemolytic disease of the fetus and newborn in some pregnancies but have little to no effect in other pregnancies. Cases are typically not detected until problems occur during pregnancy, making the availability of compatible blood a challenge.

Proteolytic enzymes are used to treat red blood cells (RBCs) to aid in complex antibody identification. Although there are many enzymes that can be used, for the purpose of this method review, enzyme-treated RBCs refers only to RBCs treated with ficin or papain. Ficin and papain can increase the sensitivity of antibody detection by modifying the RBC membrane. Enzyme treatment and test methods can be performed using one-stage or two-stage procedures. Enzyme treatment is especially useful for the differentiation of multiple antibodies, enhancement of detection of weak antibodies, and adsorption methods. In all cases, quality control is required to ensure adequate treatment of RBCs before additional testing. Ficin and papain are useful tools for both immunohematology reference laboratories and transfusion services.

Anti-D in individuals with a weak D phenotype is an unexpected finding that may require additional investigation to determine whether the anti-D is an autoantibody or alloantibody. Further investigation may also include assessment of the patient's RHD genotype and exclusion of anti-G. We present a case of an 84-year-old man with the weak D type 2 genotype who developed an unexpected anti-D along with anti-C. Individuals with the weak D type 2 genotype are thought not to be at risk for developing alloanti-D, although the distinction between alloanti-D and autoanti-D may be difficult to ascertain. Furthermore, investigations may affect transfusion recommendations. This patient was restricted to crossmatch-compatible, D-C- red blood cells even though the clinical significance of the anti-D was uncertain. This report is one of a few reported cases of an individual with the weak D type 2 genotype with demonstrable anti-D but without evidence for alloanti-D.

Autoimmune hemolytic anemia (AIHA) due to warm-reacting IgA autoantibodies is rare. Here, we explored the clinical and immunohematologic characteristics of patients suffering from IgA-associated warm AIHA (WAIHA) and their transfusion management. The 9-year study included 214 patients with WAIHA who were further classified into two groups: (1) IgA-associated WAIHA and (2) non-IgA-associated WAIHA. Clinical and laboratory details were obtained from patient files and the Hospital Information System. All immunohematologic investigations were performed following standard operating procedures and established protocols. Among the 214 patients with WAIHA, 17 (7.9%) belonged to the IgA-associated group; of these, two IgA-only WAIHA cases were found. The mean hemoglobin in this group was 5.58 g/dL, and 15 (88.2%) of these patients received a total of 32 units of packed red blood cell (RBC) transfusions. In vivo hemolytic markers were significantly abnormal in the IgA-associated WAIHA group when compared with the non-IgA group. Secondary WAIHA was found in 11 (64.7%) patients with IgA-associated WAIHA. Patients with IgA-associated WAIHA received more blood transfusions than individuals in the non-IgA group (p = 0.0004). A total of 17 (7.9%) patients with WAIHA experienced adverse events to blood transfusion. Detailed characterization of WAIHA with particular emphasis on IgA-associated and non-IgA-associated WAIHA is essential to evaluate the disease characteristics, access the degree of hemolysis, understand the immunohematologic behaviors of the antibodies, and manage blood transfusions.

Alloimmunization to K11 is an extremely rare event. However, given the potential clinical significance of K11 alloantibodies, allocating antigen-negative red blood cell (RBC) units is a clinical necessity. In brief, we report a 39-year-old woman with multiple comorbidities including a right lower-extremity, below-the-knee amputation, who developed aggressive osteomyelitis associated with continuous bloody oozing, leading to anemia. To address these issues, the patient required extremity amputation. Surgery required addressing the concomitant critical anemia (hemoglobin <5 g/dL). However, with anti-K11 (in addition to anti-Jk^a) identified, no compatible units were immediately on hand and transfusing crossmatch-incompatible, antigen-positive units was deemed too high a risk. After a national search by the American Rare Donor Program (ARDP) was unsuccessful, the ARDP identified 2 irradiated, group O, K₀ (Kell_null), Jk(a-) RBC units in Japan that were predicted to be crossmatch-compatible with the patient's plasma. The units were successfully procured and infused, without evidence of adverse reactions, and the patient was able to safely undergo amputation to save her life. This case report reviews the complexities of anti-K11 detection and confirmation, as well as the processes by which K11- RBC units may be procured, which could help others in the global transfusion community should they be faced with similar challenging cases.