Case Report: Atypical Presentation of Anti-Rg a

Transcription

1 100 Case Report: Atypical Presentation of Anti-Rg a Eiad Kahwash, Sameer S.Talwalkar, Jill Leonard, and William Lockwood Department of Pathology and Laboratory Medicine, University of Louisville, Louisville, Kentucky Abstract. The Rodgers (Rg a ) antigen is a plasma protein that binds to the red blood cell (RBC) membrane. About 2 to 3% of the transfusion-recipient white population lacks the antigen and can produce anti-rg a antibody. We report the case of a 70-yr-old man who presented with a medical history of hairy cell leukemia and profound pancytopenia that required RBC and platelet (PLT) transfusions. The patient had received 2 units of RBCs and 4 PLT concentrate pools. He was typed as O Rh(D) positive, with positive reactions in all 3-screen cells using the polyethylene glycol (PEG) indirect antiglobulin test/iat (anti-igg). Three antibody identification panels were performed, which all proved to be negative. A direct antiglobulin test and an auto-control were run, which were also negative. Since further investigations were needed, the patient s blood sample was sent to a reference laboratory where anti-rg a was identified. Since the percentage of antigen-positive cells in the red cell panel was low, crossmatch compatible units of RBCs were transfused with no discernible immediate or delayed transfusion reaction. This report should alert hospital transfusion service personnel to recognize that, although the panel cells are usually reliable for antibody identification purposes, they may not have the antigens that are present on the screening cells. (received 2 August 2004, accepted 24 November 2004) Keywords: anti-rg a, Rodgers antigen, antibody identification Introduction Several blood group antigens are not produced by the red blood cells (RBC) but are plasma constituents that adhere to the RBC membrane. Examples of these antigens include the Lewis (Le) antigens, which are glycoproteins, and the Chido/Rodgers (Ch/Rg) antigens, which are proteins carried in the plasma by the C4 complement component [1]. The Ch/Rg antibodies are uncommon and usually are clinically insignificant, as are other high-titer, low avidity antibodies (HTLA). However, since the Ch/ Rg antigens are found on 97% of RBCs, positive antibody screening tests or antibody identification panels due to such antibodies necessitate additional Address correspondence to Sameer S. Talwalkar, M.D., Department of Pathology and Laboratory Medicine, University of Louisville School of Medicine, Louisville, KY 40292, USA; s0talw01@gwise.louisville.edu; tel ; fax serological studies in order to rule out the presence of underlying clinically significant antibodies [1]. We report a case of an anti-rg a that had unexpected serological characteristics reacting only with routine screening cells but not with routine antibody identification panels. Case Report The patient is a 70-yr-old African American man with a long history of hairy cell leukemia who had received chemotherapy consisting of interferon and chenodeoxycholic acid (Chenodiol). Due to his malignant disease and its complications, the patient had profound pancytopenia and required RBC and platelet (PLT) transfusions. The patient had been transfused with 2 units of RBCs and 4 PLT pools Abbreviations. Anti-Rg = Rodgers antibody; Rg = Rodgers antigen; HTLA = high titer, low avidity; PEG = polyethylene glycol; AHG = antihuman globulin /05/ $ by the Association of Clinical Scientists, Inc.

2 Atypical presentation of anti-rg a 101 prior to the identification of anti-rg a. The patient initially typed O Rh(D)-positive; the antibody screen using polyethylene glycol (PEG) was strongly reactive (2+ to 4+) at the antihuman globulin (IgG) phase, and the direct antiglobulin test (DAT) was negative. Further serological testing, consisting of 3 red cell panels using PEG, were nonreactive including the autologous control. Testing was then performed using a solid phase technique and was found non-reactive both in the Capture-R Ready Screen and Capture-R Ready ID panel. The antibody screen with PEG was repeated using washed cells and was reactive (1+ to 2+) at the antihuman globulin (IgG) phase. The strong positive reactivity in the antibody screening cells prompted further serological investigations, for which the patient s blood sample was sent to the American Red Cross Reference Laboratory (ARC), with the subsequent identification of anti-rg a. Materials and Methods The 3-cell antibody screen (ImmucorGamma Biologics, Norcross, GA) was performed with the addition of PEG. Antibody identification (ID) panels were performed with Gamma panel (lot # , Immucor) and Panelcell-16 (lot #31173, Immucor). Testing was repeated using Capture-R for screening and the Ready-ID for panel cells (Immucor). The blood sample was sent to American Red Cross Blood Services Reference Laboratory (Columbus, OH), where screening cells from Immucor (lot #31179, Immucor) were again tested with the patient s serum. Several antigen typings were performed with the patient s cells to determine the patient s RBC phenotype. To confirm the antibody results, the patient serum was serially diluted, each dilution was neutralized with pooled plasma, and testing was performed by a gel method. Papainand dithiothreitol-treated reagent cells were also tested for reactivity with the patient s serum. Results The patient was initially typed as O Rh(D)-positive. The 3-cell antibody screen by the routine PEG indirect antiglobulin test/iat (anti-igg) was Table 1. Results of serological testing using the gel technique Screening Intermediate 5 min at Antihuman cells spin room temp. globulin SC I negative not tested 2+ a 1+ b SC II negative not tested 4+ a 2+ b SC III negative not tested 2+ a 2+ b Direct antiglobulin test negative negative not tested Control positive positive not tested a PEG enhancement; b washed cells (x 3) Table 2. Results of confirmatory serologic testing Test Results Serial titration Titer +32, score = 27 Neutralization with pooled plasma No change in reactivity Neutralization with P1 substance No change in reactivity Dithiothreitol-treated test cells No change in reactivity Papain-treated test cells Reactivity was denatured strongly reactive (2+ to 4+) with all 3 cells and the direct antiglobulin test (DAT) was negative. The antibody screen was repeated using washed (3 times) cells and was found to be reactive (1+ to 2+) by PEG- IAT (anti-igg) with all 3 antibody screening cells (Table 1). Further serological testing (consisting of antibody identification cell panels from 3 manufacturers) was non-reactive, including the autologous control. The strong positive reactivity in the antibody screen prompted further studies to rule out a high titre, low avidity antibody (HTLA). Testing by a solid phase technique performed by the ARC showed reactivity both in the Capture- R Ready 2-cell screen and the Capture-R Ready ID (6 of 13 cells). Antigen phenotyping of this patient revealed him to be negative for the following antigens: K-, S-, Fy a -, Jk b -, Le b -, P1-, and Rg a -. Additional serological investigations at ARC showed reactivity with only 5 of 30 red cells in antibody identification panels. Several antigen tests of the patient s cells showed the cells to be nonreactive with 2 sources of anti-rg. To confirm anti- Rg (Table 2), the serum was serially diluted, each

3 102 dilution was neutralized with pooled plasma, and testing was performed by a gel method. Each cell dilution that did not contain pooled plasma reacted to a titer of 32, but neutralized dilutions reacted to a titer of 8. No change in reactivity was seen with enzyme-treated cells, except for papain-treated cells that denatured the activity. Undiluted serum was also non-reactive with enzyme-treated cells. All these findings are consistent with the presence of anti- Rg a. Due to the low percentage of antibody positive cells in the red cell panel, crossmatch compatible units of RBC were transfused with no discernible immediate or delayed transfusion reaction. Discussion The Chido (Ch) and Rodgers (Rg) blood group system consists of 2 antigens that are not true RBC antigens but are adsorbed onto the RBC membrane from the surrounding plasma. Ch and Rg antibodies are epitopes on the fourth component of complement (C4), and the type-1 complement receptor carries the Knops system antigens [1,2]. Although sera from incompatible donors were usually able to inhibit the Rg antibodies in a manner similar to anti- Ch, the 2 antibodies are different [3]. Rodgers is an epitope of the C4A component of plasma complement [4]. C4-coated RBCs in 10% sucrose have been shown to react with anti-rg, proving that the antigenic determinants are within the C4d fragment [5]. These findings of the link between C4A, C4d, and Rg antigens established Rg in the major histocompatibility complex class III region on chromosome 6 [6]. Two different Rodgers determinants have been identified, in addition to WH, a determinant on a Ch/Rg hybrid requiring both Rg1 and Ch 6 [7, 8]. The ISBT Working Group on Nomenclature has assigned numeric notations Rg1 and Rg2. The Rg 1, 2 incidence is expressed in up to 95% of random selection [9] while Rg 1, -2 and Rg -1, -2 are expressed in only 2.5% each. WH is expressed in about 15% and may be detected in the heterozygous state [9]. Individuals who do not have one or more of the Rg determinants can make antibodies against the antigens they lack. However, their red blood cells are Rg positive when tested with the common multi-specific antisera [10]. Titration studies of our patient s serum showed low avidity to a titer of 32. These results suggested the presence of an HTLA-like antibody and additional studies were carried out to determine the antibody specificity. Our patient s serum was not neutralized by pooled plasma. Although inhibition of anti- Ch and anti-rg activity by soluble antigen in pooled plasma may be either complete or partial, there are reported examples where pooled plasma does not inhibit antibody reactivity due to different antigen expression by different donors [3,11]. Serum with high-titered Rg antibodies is not inhibited if the donor has high levels of Rg (C4A). Of note, other antibodies may be neutralized by the inhibition studies, so this should not be the only method used to identify anti-rg as distinct from other blood group antibodies [10]. It has been reported that using C4-coated red cells would make Rg antibody identification much easier, so that it can be distinguished readily from antibodies to other high incidence antigens [12]. This investigation was not performed on our patient s serum. Enzyme-treated cells are recommended for use to aid in identifying HTLA antibodies Ch, Rg, and JMH, whereas dithiothreitol (DTT) may be used to identify other HTLA antibodies Cs a, Yk a, McC a, and Kn a that are not destroyed by DTT [13]. Papain treatment of test cells eliminated reactivity with our patient s serum, but DTT treatment did not change the reactivity. Antibody screening tests a patient s serum against 2 or 3 group O red blood cells that have the most clinically important and commonly encountered antigens [14]. Antigen-antibody binding is promoted by using enhancement reagents like PEG, while RBCs sensitized with IgG or complement molecules require the addition of antihuman globulin (AHG) to promote agglutination [12]. Antibody ID panels are an extension of antibody screening and different manufacturers panels are routinely used for complete antibody identification. As the patient s serum reacted only with screening cells from 2 manufacturers, the manufacturers were asked about procedural differences in the preparation or preservation of their screening cells and panel cells. No unusual manufacturing process had occurred with the lot numbers that were used in our case.

4 Atypical presentation of anti-rg a 103

5 104 If possible, antibodies should be identified in order to select compatible donor units for transfusion. Although HTLA antibodies are not clinically significant but result in incompatible crossmatches, any underlying alloantibody(ies) that could be clinically significant should be identified. We therefore propose a scheme for serological identification of HTLA antibodies (Fig. 1). In conclusion, this case is interesting because the panel cells used for antibody identification did not react with the patient s serum, which was subsequently shown by antibody-screening tests to have a specific antibody. It is unusual that the 3 antibody-screening panels had this common antigen, while none of the cells used in routine antibody identification panels were reactive. Therefore, it is important to be aware that (a) the panel cells that are usually reliable for antibody identification purposes may not have the antigens that are present on the screening cells, and (b) delay in providing blood for transfusion to a patient harboring clinically insignificant antibodies may occur in such cases. Acknowledgement This study was supported in part by grant #22-07 from the Norton Healthcare Community Trust Fund. References 1. Issitt PD, Anstee DJ. The Chido-Rodgers blood group system. In: Applied Blood Group Serology, 4th ed, Montgomery Scientific Publishers, Durham, NC, 1998; pp Moulds JM. Blood Group, Review/Update: Rodgers, Chido and Knops. American Association of Blood Banks, Bethesda, MD, 1992; pp Longester G, Giles CM. A new antibody specificity, anti- Rg a, reacting with a red cell and serum antigen. Vox Sang 1976;30: O Neill GJ, Yang SY, Tegoli J, Bergr R, Dupont B. Chido and Rodgers blood groups are distinct antigenic components of human complement C4. Nature 1978;273: Tilley CA, Romans DG, Crookston MC. Localization of Chido and Rodgers determinants to the C4d fragment of human C4. Nature 1978;276: Moulds JM. Rare blood group phenotypes as models for future investigation. In: Progress in Immunohematology (Moor SB, Ed), American Association of Blood Banks, Arlington, VA, 1988; pp Giles CM. Three Chido determinants detected on the B5Rg+ allotype of human C4: Their expression in Chtyped donors and families. Human Immunol 1987;18: Giles CM, Jones JW. A new antigenic determinant for C4 of relatively low frequency. Immunogenetics 1987; 26: Giles CM. Antigenic determinants of human C4, Rodgers and Chido. Exp Clin Immunogenetics 1988;5: Moulds, JM, Laird-Fryer, B, eds. Blood Groups: Chido/ Rodgers, Knops/McCoy/York and Cromer. American Association of Blood Banks, Bethesda, MD, 1992; pp Giles CM. Partial inhibition of anti-rg and anti-ch reagents. I. Assessment for Rg/Ch typing by inhibition. Vox Sang 1985;48: Judd WJ, Kraemer K, Moulds JJ. The rapid identification of Chido and Rodgers antibodies using C4d-coated red blood cells. Transfusion 1981;21: Rolih SD. High-titer, low-avidity (HTLA) antibodies and antigens: a review. Trans Med Rev 1989;III: Harmening DM. The antibody screen. In: Modern Blood Banking and Transfusion Practices, 3rd ed, Davis, Philadelphia, 1994; pp