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IgA-type macroprolactin among 130 patients with macroprolactinemia
Masayuki Ishihara1, Naoki Hattori1, Norito Nishiyama1,2
1Department of Orthopedic Surgery, Kansai Medical University, Osaka, Japan.
Insights
IgA-type macroprolactin (macro-PRL) exists, though IgG-type macro-PRL is most common. This study clarifies the prevalence and characteristics of different macro-PRL types in patients.
Area of Science:
- Endocrinology
- Immunology
- Clinical Chemistry
Background:
- Macroprolactin (macro-PRL) is a complex of prolactin (PRL) with immunoglobulin G (IgG).
- The existence and prevalence of IgA-type macro-PRL have not been clearly defined.
Purpose of the Study:
- To determine if IgA-type macro-PRL exists.
- To investigate the prevalence of IgA-type macro-PRL compared to IgG-type.
- To analyze differences in laboratory data between macro-PRL types.
Main Methods:
- Analyzed 130 patients diagnosed with macroprolactinemia using polyethylene glycol precipitation and gel filtration chromatography (GFC).
- Identified IgA-type and IgG-type macro-PRLs using Jacalin column/SDS-PAGE and protein G columns.
- Utilized SDS-PAGE with IgA antibody and western blotting for identification.
Main Results:
- Confirmed the existence of IgA-type macro-PRL.
- Prevalence rates: 83.8% IgG-type, 7.7% IgA-type, 5.4% non-IgA/non-IgG, and 3.1% IgA plus IgG.
- No significant differences in PRL or macro-PRL ratios between IgA- and IgG-type macro-PRLs, but lower ratios in non-IgA/non-IgG type.
Conclusions:
- IgA-type macroprolactin has been demonstrated to exist.
- IgG-type macro-PRL is the most prevalent form.
- Prevalence order: IgG-type > IgA-type > non-IgA/non-IgG > IgA plus IgG.
Objectives:
Macroprolactin (macro-PRL) mostly comprises a complex of PRL with IgG. The aim of this study was to clarify whether IgA-type macro-PRL exists and, if so, to elucidate the prevalence of and differences in laboratory data from IgG-type.
Methods:
One hundred thirty patients with macroprolactinemia who were diagnosed through screening via the polyethylene glycol precipitation method followed by confirmation using gel filtration chromatography (GFC) were examined. IgA-type and IgG-type macro-PRLs were identified via Jacalin column/SDS‒PAGE and protein G columns, respectively.
Results:
SDS‒PAGE under nonreducing conditions followed by western blotting with an IgA antibody revealed that the fraction bound to the Jacalin column was actually IgA. The PRL band was detected at the same position as the IgA band, which was purified with a Jacalin column, suggesting that PRL was bound to IgA. The finding that the PRL band was observed not only at the same position as IgA but also at the same position as the 23 kDa PRL reference suggested that some PRL dissociated from IgA during SDS‒PAGE. The prevalence rates of macro-PRL of only IgA, IgA plus IgG, only IgG, and non-IgA/non-IgG types were 7.7, 3.1, 83.8, and 5.4 %, respectively. Neither the PEG precipitation ratios of PRL nor the macro-PRL ratios on GFC differed between IgA- and IgG-type macro-PRLs, whereas both ratios were significantly lower in non-IgA/non-IgG-type macro-PRL.
Conclusions:
IgA-type macro-PRL was demonstrated to exist. IgG-type macro-PRL was most prevalent, followed by IgA, non-IgA/non-IgG and IgA plus IgG-type macro-PRLs.
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