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Abstract Herein, we report a case of naturally occurring anti-Leb alloantibody identified in the plasma of a first time voluntary blood donor. The immunohematology workup was done on the pilot sample tubes collected during blood donation by the conventional tube technique and using ID-Micro Column System Glass Beads card (anti-IgG, C3d; Ortho-Clinical Diagnostics, Raritan, New Jersey, USA). Blood group of the donor was confirmed to be B RhD positive, and the alloantibody in his plasma was identified as anti-Leb, having clinically significant characteristics. Since in this particular case, anti-Leb was IgM and IgG in nature, it was clinically significant and can lead to hemolytic transfusion reaction, especially if such fresh frozen plasma unit is transfused to Leb negative patients.
Keywords: Anti-Leb antibody, blood donor, hemolytic transfusion reaction
How to cite this article: Introduction 
Antibodies to the Lewis blood group antigens are primarily formed as naturally occurring IgM immunoglobulin, sometimes, however, may have an IgG component with a few rare examples of IgG type.[1],[2],[3] They most often occur in the sera of Le (a-b-) individuals and may contain a mixture of anti-Lea, anti-Leb, and anti-Leab (an antibody capable of recognizing both Le (a+) and Le (b+) on the red blood cells (RBCs).[1] Anti Lewis antibodies rarely cause acute hemolytic transfusion reactions since they usually do not react at 37°C. In addition, transfused RBCs often lose their Lewis antigens into the recipient's plasma.[4] Furthermore, the Lewis antigens being present as the blood plasma antigen, the antibody in the recipient, if present, gets neutralized before reacting with the transfused RBCs.[4] Herein we report a case of naturally occurring anti-Leb alloantibody identified in the plasma of a first time voluntary blood donor.
Materials and Methods The blood group of the donor was done by the conventional tube technique (CTT) on the pilot sample tubes collected during blood donation. Further immunohematology (IH) workup included direct and indirect antiglobulin tests with polyspecific antihuman globulin (AHG-IgG+C3d) performed by CTT as well as by column agglutination technique (CAT) using ID Micro Column System Glass Beads card (anti IgG, C3 d; Ortho-Clinical Diagnostics, Raritan, New Jersey, USA).
His blood sample was sent to the reference laboratory for antibody identification and further workup.
Results A 19-year-old male, the first time donor donated blood in our department of transfusion medicine. There were no relevant histories of any recent infection or any chronic disease, transfusion, or drug intake. Blood group performed in IH laboratory showed B RhD positive by forward (cell) grouping by CTT. In reverse (serum) grouping, there was agglutination (1+) with pooled group O red cells. The indirect antiglobulin test (IAT) was positive (2+ and 3+ by CTT and CAT respectively) while direct antiglobulin test (DAT) and auto-control were found to be negative.
The results from the reference laboratory confirmed his blood group to be B RhD positive and the alloantibody in his plasma was identified as anti-Leb, having clinically significant features, reactive at the broad thermal amplitude of 22°C–37°C. IgM and IgG antibody titers of anti Leb were 2 and 4, respectively, by CAT. Donor's RBCs were typed as Leb negative. The most frequent alloantibodies (0.13%) identified among alloimmunized blood donors in our center, were of Lewis blood group system (14/10,390).
Discussion Antibodies in the Lewis blood group system are capable of activating complement and occasionally cause in vivo and or in vitro hemolysis.[4] Study by Thakral et al. has demonstrated the frequency of Le (a+b-), Le(a-b+), and Le(a-b-) in the Indian population to be 20.8%, 60.6%, and 18.6%, respectively.[5] Similarly, Nanu and Thapliyal found the frequency to be 13.3%, 61.0%, and 23.9%, respectively.[6] In the majority of cases, Lewis antibodies are naturally occurring, however, sometimes RBC transfusion may stimulate their production. Promwong et al. studied alloantibodies in the donor population where they found a frequency of anti-Leb to be 18.9%.[7] Keokhamphoui et al. found it to be 0.42%.[8] Garg et al. and Makroo et al. found these frequencies to be 2.1% and 1.31%, respectively.[9],[10] The prevalence of anti-Leb among our donor population was found to be 0.13%.
Antibodies to Lewis blood group system are rarely clinically significant. In this case, there was a naturally occurring alloanti Leb identified in the donor's plasma with both IgM and IgG components,, having a broad thermal amplitude (22°C–37°C), thereby making it clinically significant. Since in this particular case, anti-Leb was IgM and IgG in nature, it was clinically significant and can lead to hemolytic transfusion reaction, especially if such fresh frozen plasma unit is transfused to Leb negative patients. A special IH report indicating the presence of alloanti Leb in his plasma with an advice to transfuse B RhD positive, Leb antigen negative AHG (anti human globulin) phase crossmatch compatible red cells in case any such need arises in future as well as to refrain from further blood donations.
Conclusion Screening for the presence of alloantibodies in donated blood is a vital step to provide compatible blood to the recipients.
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References 
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CheckDOI: 10.4103/ajts.AJTS_68_19
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