A new look at an old case: An auto-anti-P with pseudo-LKE activity

Laura Cooling

doi:10.5348/ijbti-2013-10-oa-1

Abstract

Aims: LKE is a high-incidence, minor RBC glycosphingolipid, related to both Pk and P antigens. Approximately 1% individuals are LKE-negative. However, antibodies against LKE are rare, with only six cases mentioned in literature. Past examples of anti-LKE have relied on serologic testing, with no direct testing against RBC glycosphingolipid (GSL). To test a historical 'anti-LKE' against a panel of RBC and glycosphingolipid standards by high performance thin layer chromatography and standard serology. Methods: Serum samples included human polyclonal anti-LKE, alloanti-P, alloanti-PP1Pk and untransfused controls. Hemagglutination was performed by gel method with ficin-treated RBC of known LKE, P and P1 phenotype. P antigen expression was determined by titration with a well characterized alloanti-P. Antibody specificity was determined by incubating serum against glycosphingolipids on high performance thin layer chromatography plates. Results: The patient's serum reacted with most LKE+ RBC but not ficin-treated p, Pk, or LKE-negative donors, consistent with an anti-LKE. However, on direct testing, the patient's antibody failed to recognize monosialogalactosylgloboside, the LKE antigen. The patient's serum did recognize globoside (P) antigen. This was confirmed by hemagglutination, which showed a correlation between LKE phenotype, P antigen expression and serum reactivity. The patient's weak auto-anti-P was not inhibited by solubilized globoside. Conclusion: This historical anti-LKE is an auto-anti-P with 'pseudo-LKE' activity due to differences in P antigen expression between LKE+ and LKE-donors.

Highlights

The LKE antigen or ‘Luke antigen on erythrocytes’ is a highincidence red cell (RBC) antigen, present on 99% of donors (Table 1)
The LKE antigen has been identified as monosialogalactosylgloboside (MSGG) or stagespecific embryonic antigen4, a globo family ganglioside [2]
A weak antiP1 was identified in the indirect antiglobulin test (IAT) by tube: No antiP1 was observed by gel method using buffered gel cards

Summary

Introduction

The LKE antigen or ‘Luke antigen on erythrocytes’ is a highincidence red cell (RBC) antigen, present on 99% of donors (Table 1). Like P1 antigen, LKE has variable expression, with 8090% typing LKEstrong (LKES), 1020% typing LKEweak (LKEW) and 12% typing LKEnegative (LKEN) depending on the population and reagent used for typing [13]. The LKE antigen has been identified as monosialogalactosylgloboside (MSGG) or stagespecific embryonic antigen4, a globo family ganglioside [2]. Www.ijbti.com antigens, which are upstream substrates necessary for MSGG synthesis (Figure 1). P and Pk RBC are always LKEnegative (LKEN) due to the complete absence of P/Gb4, Gb5 and MSGG (Table 1). Normal P+, LKEN donors still have low levels of MSGG when examined by sensitive methods [3, 4]

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Discussion

Conclusion