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Technical Briefs: Sayed M.H. Sadrzadeh, Yasi Saffari, and Jafar Bozorgmehr Haptoglobin Phenotypes in Epilepsy Clin Chem 2004; 50: 1095-1097 [Full text] [PDF]

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Affinity of Haptoglobin Polymers for Hemoglobin

Toshio Okazaki, Toshiaki Nagai, and Tatsuo Nagai   (24 January 2005)

Affinity of Haptoglobin Polymers for Hemoglobin 24 January 2005
Toshio Okazaki, Associate Professor Kitasato University School of Allied Health Sciences, Toshiaki Nagai, and Tatsuo Nagai Send letter to journal: Re: Affinity of Haptoglobin Polymers for Hemoglobin okazaki{at}cc.ahs.kitasato-u.ac.jp Toshio Okazaki, et al.	Sadrzadeh et al. (1) presented a very interesting report that haptoglobin (Hp) phenotype 2-2 was significantly associated with recurrent seizures. However, it is not clear what is the difference that Hp phenotypes exert on hemoglobin (Hb) metabolism. It is known that Hp2-2 complexed with free hemoglobin has a high affinity for CD163 receptors on macrophages (2). However, as the molecular weight of Hp2-2 polymers increases, the affinity of the Hp polymer for Hb becomes weaker (3). It is doubtful whether, in Hp2-2 types, Hp-Hb complexes are more easily taken into macrophages than other phenotypes. In the Hp2-2 type, it might be easier to have damage caused by free Hb, because the Hp concentration in Hp2-2 type is lower than that of other phenotypes (1,3), and the Hp2-2 type easily develops hypohaptoglobulinemia. We previously encountered a heterozygote of the rare Hp2-Johnson type in whom the Hp concentration was about half that of the Hp2-2 type and showed a molecular weight larger than that of Hp2-2 polymers (4). It is easy for this type to be misidentified as ahaptoglobulinemia. If Hb is involved in the etiology of seizures, there will be a possibility that recurrent seizures occur in the Hp2-Johnson type more easily than in other common Hp phenotypes. References 1) Sadrzadeh SMH, Saffari Y, Bozorgmehr J. Haptoglobin phenotypes in epilepsy. Clin Chem 2004;50:1095-7. 2) kristiansen M, Graversen JH, Jacobsen C, Sonne O, Hoffman HJ, Law SK, et al. Identification of the haemoglobin scavenger receptor. Nature 2001;409:198-201. 3) Okazaki T, Yanagisawa Y, Nagai T. Analysis of the affinity of each haptoglobin polymer for hemoglobin by two-dimensional affinity electrophoresis. Clin Chim Acta 1997;258:137-44. 4) Okazaki T, Omura K, Kadohno N, Yamamori S, Yanagisawa Y, Nagai T. Identification and quantitative analysis of haptoglobin Johnson heterozygote. Clin Chim Acta 1998;270:169-76.