Immunochemical properties of alpha-fetoprotein (AFP) and antibodies to autologous AFP

A Microfluidic Chip-Based MRS Immunosensor for Biomarker Detection via Enzyme-Mediated Nanoparticle Assembly

Conventional immunoassay methods have their common defects, such as tedious processing steps and inadequate sensitivity, in detecting whole blood. To overcome the above problems, we report a microfluidic chip-based magnetic relaxation switching (MRS) immunosensor via enzyme-mediated nanoparticles to simplify operation and amplify the signal in detecting whole blood samples. In the silver mirror reaction with catalase (CAT) as the catalyst, H2O2 can effectively control the production of Ag NPs. The amount of Ag NPs formed further affects the degree of aggregation of magnetic nanoparticles (MNPS), which gives rise to the changes of transverse relaxation time (T2). Both sample addition and reagent reaction are carried out in the microfluidic chip, thereby saving time and reagent consumption. We also successfully apply the sensor to detect alpha-fetoprotein (AFP) in real samples with a satisfied limit of detection (LOD = 0.56 ng/ml), which is superior to the conventional ELISA.

Alpha-fetoprotein structure and function: relevance to isoforms, epitopes, and conformational variants

Mammalian alpha-fetoprotein (AFP) is classified as a member of the albuminoid gene superfamily consisting of albumin, AFP, vitamin D (Gc) protein, and alpha-albumin. Molecular variants of AFP have long been reported in the biomedical literature. Early studies identified isoelectric pH isoforms and lectin-binding variants of AFP, which differed in their physicochemical properties, but not in amino acid composition. Genetic variants of AFP, differing in mRNA kilobase length, were later extensively described in rodent models during fetal/perinatal stages, carcinogenesis, and organ regeneration. With the advent of monoclonal antibodies in the early 1980s, multiple antigenic epitopes on native AFP were detected and categorized, culminating in the identification of six to seven major epitopes. During this period, various AFP-binding proteins and receptors were reported to inhibit certain AFP immunoreactions. Concomittantly, human and rodent AFP were cloned and the amino acid sequences of the translated proteins were divulged. Once the amino acid composition of the AFP molecule was known, enzymatic fragments could be identified and synthetic peptide segments synthesized. Following discovery of the molten globule form in 1981, the existence of transitory, intermediate forms of AFP were acknowledged and their physiological significance was realized. In the present review, the various isoforms and variants of AFP are discussed in light of their potential biological relevance.

Human alpha-fetoprotein (AFP) causes a selective down regulation of monocyte MHC class II molecules without altering other induced or noninduced monocyte markers or functions in monocytoid cell lines

Human alpha-fetoprotein (AFP) purified from human amniotic fluid was investigated for its effect on human monocytoid cell lines, including U 937 cells with established subclones. The impact of AFP on the expression of surface markers (MHC class I and II, CD4, CD18, CD45, Fc receptors for IgG) was analyzed using known inducers of monocyte-macrophage differentiation such as phorbol esters and IFN-gamma. Furthermore we investigated the effect of AFP on the induction of macrophage antibody-dependent cell-mediated cytolytic activity (ADCC). AFP did selectively induce a rapid down regulation of surface MHC class II expression. No evidence of alterations was found in the endogenous or differentiation-induced expression of other markers on the surface on monocytes, nor did AFP affect the functional maturation of surface Fc receptors or the ability to express ADCC.

Monoclonal antibodies to different epitopes of human alpha-fetoprotein (AFP)

Monoclonal antibodies specific for human alpha-fetoprotein (AFP) were produced by the hybridoma technique. By using solid-phase immunofluorescence and radioimmunoassays, the antibodies were proven to distinguish 4 different epitopes on the AFP molecule.