A fatal hemolytic transfusion reaction resulted because a monoclonal anti-B that detected acquired B antigen was used to type red cells from an elderly man whose serum had weak anti-B that was not detected by abbreviated compatibility testing.

Based on the estimated number of screening events with C873 RBCs, the incidence of anti-TSEN is approximately 1 in 20,000 sera. The antibody is found in patients with and without documented exposure to allogeneic RBCs. All known examples of anti-TSEN are IgG, but their clinical significance is not known.

Background: TSEN (MNS33) is a low-incidence antigen in the MNS blood group system encoded by hybrid glycophorin genes. TSEN is expressed by a unique amino acid sequence that results from the junction of GPA⁵⁸ to GPB²⁷, if the GPB carries S antigen. Until this study, only one example of anti-TSEN had been found. Antibody screening red blood cells (RBCs) positive for both S and s (ref. No. C873) reacted with four patient sera. Initially, the RBCs had been typed as S+s+, but later were typed as S–s+ in another laboratory. Two other RBC samples, one from a volunteer blood donor (D.L.), the other from a patient whose serum contained anti-En^aFR (J.S.), also gave anomalous results when tested with anti-S. We suspected the presence of TSEN-positive hybrids on all three RBC samples. Materials and Methods: Reactive sera (O.B., E.C., S.K., R.F.) were tested against RBCs with normal MNS phenotypes and with TSEN-positive RBCs. The RBCs of D.L., J.S. and C873 were tested with anti-S whose reactivity with S+s+ TSEN+ RBCs had been established previously, and with the original example of anti-TSEN. Immunoblotting was performed on the C873, D.L. and J.S. RBC membranes using a monoclonal antibody to an epitope common to both glycophorin A and glycophorin B. Results: The sera from O.B., E.C., S.K. and R.F. were strongly reactive on the indirect antiglobulin test with TSEN+ RBCs. The RBCs of C873, D.L. and J.S. were typed as TSEN+. Immunoblotting pattern of D.L. and C873 were consistent with TSEN heterozygotes, while that of J.S. was consistent with a TSEN homozygote. Conclusions: Based on the estimated number of screening events with C873 RBCs, the incidence of anti-TSEN is approximately 1 in 20,000 sera. The antibody is found in patients with and without documented exposure to allogeneic RBCs. All known examples of anti-TSEN are IgG, but their clinical significance is not known.

Although antibodies to the Di b antigen are generally considered to be of potential clinical significance, we know of no reports assessing the clinical significance of anti-Di b (in vivo or in vitro). We report on an 88-year-old Japanese male gastrectomy patient who had alloanti-Di b . After transfusion of two Di(b-) units, three Di(b+) units had to be transfused, and there were no clinical signs of acute hemolysis. Di(b+) RBC survival was followed retrospectively by flow cytometry. On days 1, 7, and 10, the percent of circulating Di(b+) RBCs was determined to be 39, 30, and 11 percent, respectively, compared to an expected 49, 43, and 41 percent based on calculations. The Di(b+) RBCs appear to have been tolerated for about 6 days, then were removed from the circulation. Direct anti-IgG tests were 1-2+ mixed field with all posttransfusion samples. Monocyte monolayer assays (MMAs), which have been reported to predict the clinical significance of alloantibodies, gave borderline positive results. MMA results using sera from days 0, 3, and 9 were 2.7 and 5.5, 0.8 and 4.8, and 3.0 and 3.7 percent, respectively, without and with added fresh normal serum as a source of complement (clinical significance = > 3% reactivity). The subclass of the anti-Di b was IgG1. This is the first documentation of the clinical significance of an anti-Di b . Immunohematology 1997;13:93-96.

Clinical and hematologic evidence of warm autoimmune hemolytic anemia (AIHA) is present in some patients whose direct antiglobulin test (DAT) is negative. The most common causes for AIHA associated with a negative DAT are RBC-bound IgG below the sensitivity threshold of the DAT, RBC-bound IgA and IgM not detectable by routine reagents, and low-affinity IgG that dissociates during the testing process. Samples submitted from 800 patients with hemolytic anemia and a negative DAT were tested by an antiglobulin sera (AGS) panel of anti-IgG, anti-C3, anti-IgM, and anti-IgA by a routine DAT. Additional tests included a direct Polybrene test to detect small amounts of RBCbound IgG, a cold-wash technique to detect low-affinity IgG, and a DAT by gel test with anti-IgG. A positive result was obtained with at least one method for 431 (54%) of 800 specimens tested. The AGS panel was positive for 400 (50%) of samples, with IgG or C3 or both accounting for reactivity in 48 percent. IgA alone was found on 2 percent of samples; IgM was never found alone. Lowaffinity IgG was found on 37 (5%) samples. The direct Polybrene test was the only positive test for 15 (2%) samples. The gel anti-IgG test was never the only positive test. Clinical correlations for these data were not available; however, previously published correlations suggest a positive predictive value for tests that extend routine DAT methods in patients with DAT-negative AIHA. Immunohematology 2010;26:156-60.