Immunochemical property of human haptoglobin phenotypes: determination of plasma haptoglobin using type-matched standards.
OBJECTIVE
Haptoglobin (Hp) phenotypes 1-1, 2-1, and 2-2 are associated with inflammatory diseases. Since their biochemical structures are rather heterogeneous, it is necessary to accurately determine the plasma Hp levels.


METHODS
Immunodiffusion, immunoturbidimetric, and noncompetitive ELISA were conducted to determine the differences in immunoreactivity among Hp phenotypes and to verify that such difference may significantly affect the outcome of Hp determinations. A novel ELISA using phenotype-matched calibrators was performed to compared with a commercial GenWay ELISA kit using a single calibrator in normal healthy males.


RESULTS
In immunodiffusion and immunoturbidimetric assays, the immunoreactivity of Hp 1-1 was markedly higher than 2-1 and 2-2, while an opposite result was observed using an ELISA. The latter was primarily due to the repeated antigenic epitopes in polymeric 2-1 and 2-2. Thus, Hp levels could be significantly over- or underestimated depending on the method. An accurate ELISA could be achieved when using each type-specific Hp calibrator matched to each type subject. We show the mean levels of Hp 1-1 subjects (n=16; 184+/-42 mg/dL) to be significantly and differentially greater than 2-1 (n=28; 153+/-55 mg/dL) (p<0.05) and 2-2 (n=24; 93+/-54 mg/dL) (p<0.01) subjects.


CONCLUSIONS
Due to the diverse immunochemical structure among the Hp types, phenotyping should be performed in all the patients and a type-matched Hp calibrator should be used in clinical Hp determination.
Cheng
Tsai-Mu
TM
College of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan, ROC.
Pan
Ju-Pin
JP
Lai
Shiau-Ting
ST
Kao
Li-Pin
LP
Lin
Hong-Huei
HH
Mao
Simon J T
SJ
D000368:Aged; D045744:Cell Line, Tumor; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006242:Haptoglobins / Q000235:genetics* / Q000378:metabolism* / Q000592:standards; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012015:Reference Standards; D020133:Reverse Transcriptase Polymerase Chain Reaction
C485359:HP protein, human; D006242:Haptoglobins; D012333:RNA, Messenger