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

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.