Association between complement regulatory protein factor H and AM34 antigen, detected in senile plaques.
BACKGROUND
We have previously shown that monoclonal antibody AM34, which is reactive with senile plaques, may recognize the C terminus of complement factor H. In this study, we investigated the expression of factor H in tissue from a human brain and the relation between AM34 antigen and factor H.


METHODS
Total ribonucleic acid (RNA) was extracted from a normal human brain. A reverse transcriptase-polymerase chain reaction method was employed for detecting messenger RNAs coding for factor H and related proteins. Protein extracts from a normal human brain were also analyzed to detect factor H and related proteins by means of Western blotting. The cerebrospinal fluid from an Alzheimer's disease patient was immunoprecipitated with AM34 and anti-factor-H antibodies, and then it was subjected to gel electrophoresis followed by immunoblotting with AM34 and anti-factor-H antibodies.


RESULTS
26 clones of complementary DNA fragment were obtained by reverse transcriptase-polymerase chain reaction. Among them, seven clones were identical to factor H, and the others were related proteins and unreported sequences. A Western blot analysis of protein extracts from the normal brain tissue exhibited a 150-kd band, indicating the presence of factor H. AM34 was immunoreactive with the 150-kd molecule contained in the immunoprecipitates with anti-factor H antibodies, and vice versa. These results suggest that AM34 antigen could be identical to complement factor H.


CONCLUSIONS
The results of our experiments indicate that factor H is possibly detected in the human brain, and that the AM34 antibody could recognize factor H. Because AM34 is capable of staining senile plaques positively, factor H is suggested to be associated with senile plaques in the human brain.
Honda
S
S
First Department of Internal Medicine, Sapporo Medical University, Japan.
Itoh
F
F
Yoshimoto
M
M
Ohno
S
S
Hinoda
Y
Y
Imai
K
K
D000368:Aged; D000544:Alzheimer Disease / Q000378:metabolism; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D001923:Brain Chemistry / Q000502:physiology; D002102:Cadaver; D017242:Complement Factor H / Q000378:metabolism*; D006801:Humans; D007124:Immunoenzyme Techniques; D058225:Plaque, Amyloid / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000911:Antibodies, Monoclonal; C493495:CFH protein, human; D012333:RNA, Messenger; D017242:Complement Factor H