Placental alkaline phosphatase types and transplacental IgG transport

Diagnostic Capability of Cerebrospinal Fluid-Placental Alkaline Phosphatase Value in Intracranial Germ Cell Tumor

OBJECTIVE

Most types of intracranial germ cell tumors (IGCTs) are sensitive to chemoradiation. However, biopsy specimens are usually small and thus cannot be used for obtaining an accurate pathological diagnosis. Recently, the cerebrospinal fluid (CSF) placental alkaline phosphatase (PLAP) value has been considered a new biomarker of IGCTs. The present study aimed to evaluate the discriminatory characteristics of the CSF-PLAP value upon diagnosis and at the time of recurrence in patients with IGCTs.

METHODS

Between 2015 and 2019, this study included 37 patients with tumors located in the intraventricular and/or periventricular region. The CSF-PLAP level was assessed before the patients received any treatment. The PLAP level was evaluated during and after first-line chemoradiotherapy in 7 patients with IGCTs. The CSF-PLAP values were compared according to histological diagnosis, and the correlation between these values and radiographical features was assessed. The CSF-PLAP values of 6 patients with IGCTs with suspected recurrence were evaluated based on neuroimaging findings.

RESULTS

The CSF-PLAP values were significantly higher in patients with IGCTs than in those with other types of brain tumor (n = 19 vs. 18; median: 359.0 vs. <8.0 pg/mL). The specificity and sensitivity were 88 and 95%, respectively, with a cutoff value of 8.0 pg/mL. In patients with IGCT, the CSF-PLAP value was higher in patients with germinoma than in those with nongerminomatous germ cell tumors (n = 12 vs. 7; median: 415.0 vs. 359.0 pg/mL). Regarding the time course, the CSF-PLAP value decreased to below the detection limit after the reception of first-line chemoradiotherapy in all 7 patients. A significant correlation was observed between the initial CSF-PLAP value and the tumor reduction volume after receiving first-line chemoradiotherapy (p < 0.0003, R2 = 0.6165, logY = 1.202logX - 1.727). Among the patients with suspected IGCT recurrence (n = 6), the CSF-PLAP value was high in patients with recurrence (n = 3; median: 259.0 pg/mL), and that in patients (n = 3) without recurrence was below the lower detection limit.

CONCLUSIONS

The CSF-PLAP level is a useful biomarker during the initial diagnosis of IGCTs and at the time of recurrence. It may be associated with the volume of germinomatous components of tumors.

Specific immunoassays for placental alkaline phosphatase as a tumor marker

Human placental (hPLAP) and germ cell (PLAP-like) alkaline phosphatases are polymorphic and heat-stable enzymes. This study was designed to develop specific immunoassays for quantifying hPLAP and PLAP-like enzyme activity (EA) in sera of cancer patients, pregnant women, or smokers. Polyclonal sheep anti-hPLAP antibodies were purified by affinity chromatography with whole hPLAP protein (ICA-PLAP assay) or a synthetic peptide (aa 57–71) of hPLAP (ICA-PEP assay); the working range was 0.1–11 U/L and cutoff value was 0.2 U/L EA for nonsmokers. The intra- and interassay coefficients of variation were 3.7%–6.5% (ICA-PLAP assay) and 9.0%–9.9% (ICA-PEP assay). An insignificant cross-reactivity was noted for high levels of unheated intestinal alkaline phosphatase in ICA-PEP assay. A positive correlation between the regression of tumor size and EA was noted in a child with embryonal carcinoma. It can be concluded that ICA-PEP assay is more specific than ICA-PLAP, which is still useful to detect other PLAP/PLAP-like phenotypes.

Placental Alkaline Phosphatase (PLAP) Enzyme Activity and Binding to IgG in Chagas' Disease

Placentas and plasma from women with and without Chagas' disease and cultures of human placental villi with Trypanosoma cruzi, neuraminidase, phospholipase A2 and phospholipase C were analyzed in order to verify if the alterations in placental alkaline phosphatase (PLAP) enzyme activity are caused by T. cruzi as observed in previous works. As IgG receptivity happens to be one of the proposed functions of PLAP, general IgG binding ability of the placentas treated with the mentioned enzymes, which are present on the parasite's surface, were also tested. The phospholipases caused an increase of PLAP's enzyme activity in the supernatant of infected placentas and a decrease of enzyme activity in the membrane of cultured placentas, therefore suggesting the cleavage of PLAP by parasitic enzymes. Desialylation could also partially inhibit PLAP's enzyme activity in supernatant and membrane of placenta culture. Placentas from healthy patients presented higher IgG receptivity than those from patients with Chagas' disease. In vitro infection of healthy placentas with T. cruzi caused no difference in IgG receptivity in placental sections with respect to controls but the phospholipases and neuraminidase increased the IgG receptivity of cultured placentas. The IgG transference index was higher for patients with Chagas' disease than for those without it. Although binding to IgG does not completely inhibit the enzyme activity of PLAP, it interferes with the enzyme activity of PLAP. We concluded that the enzymes on the surface of T. cruzi trypomastigotes can not only affect PLAP's enzyme activity but also increase the IgG binding ability of the placenta and this can be related to the actions of neuraminidase-transsialidase, phospholipase A2 and phospholipase C on the parasite surface. The modification of PLAP from women with Chagas' disease should be considered as a result of multiple factors.

Role of placental alkaline phosphatase in the interaction between human placental trophoblast and Trypanosoma cruzi

Congenital Chagas disease, due to the intracellular parasite Trypanosoma cruzi, is associated with premature labor, miscarriage, and placentitis. Human enzyme placental alkaline phosphatase (PLAP) (EC 3.1.3.1.) is membrane-anchored through glycosylphosphatidylinositol (GPI). PLAP is present in plasma in late pregnancy, 36 to 40 weeks; there are lower levels in maternal Chagas disease. Infants born to such mothers may have congenital Chagas disease. Human placental villi (PV) were treated with phospholipase-C (PL-C) and then cultured with T. cruzi to determine the effect of the parasites on PLAP activity as an in vitro model. There is less PLAP activity after treatment by PL-C and during culture with T. cruzi. Pretreatment of PV with PL-C before culture with T. cruzi yielded essentially normal specific activity of PLAP and prevented or greatly reduced infective penetration of villi by parasites. The results are consistent with a pathogenetic role for placental alkaline phosphatase in congenital Chagas disease. Receptor activation of membrane attachment to PLAP may be a device used by T. cruzi to enable parasite invasion of human trophoblast.

Human placental Fc receptors and the transmission of antibodies from mother to fetus

During human pregnancy, maternal IgG is transported across the placenta to the fetus. On the way, some maternal antibodies against fetal antigens are removed as immune complexes. The placenta contains several known Fc receptors and also other proteins that bind immunoglobulins. A consideration of the binding properties and distribution of these proteins suggests that the neonated Fc receptor (FcRn) transports IgG across the syncytiotrophoblast, and possibly the fetal blood vessel endothelium. Fc gamma RI, Fc gamma RII and Fc gamma RIII on Hofbauer cells in the stroma probably clear immune complexes, together with Fc gamma RII on endothelial cells.

Human placental Fc gamma-binding proteins in the maternofetal transfer of IgG

Annexin II, a member of the annexin family of Ca2+ and phospholipid binding proteins, is present in human placenta. Placental annexin II has low affinity FcR activity, and is present as a heterotetramere on syncytiotrophoblast apical cell membrane extracellular surface. In addition to annexin II, transmembraneous leukocyte FcRIII is present on syncytiotrophoblast apical membrane. Either one, or both molecules may mediate the binding of IgG and thereby facilitate its transport through the syncytiotrophoblast layer. However, the presence of other maternal plasma proteins in syncytiotrophoblasts that are not transported to the human fetus is suggestive of nonspecific fluid phase endocytosis. The MHC class I like FcR, similar to the receptor found in neonatal rodent intestine, FcRn, is present intracellularly in human syncytiotrophoblasts, as is its light chain beta 2-microglobulin. The hFcRn is not detected on the apical plasma membrane. The placental hFcRn co-localizes with IgG in syncytiotrophoblast granules. It is likely that hFcRn binds and transcytoses IgG through the syncytiotrophoblast. Protected transfer of IgG may occur within syncytiotrophoblast endocytotic vesicles prior to release in the villous stroma and subsequent translocation into the lumen of fetal stem vessels by uptake and transport in endothelial caveolae.

Moors and Christians: an example of multivariate analysis applied to human blood-groups

Published data on the frequencies of the alleles of the ABO, MNS, and Rh systems for populations in the western Mediterranean region are analysed by the multivariate statistical methods of canonical variates, principal components, principal coordinates, correspondence analysis and discriminant functions. It is shown that there is a 'Moorish substrate' in the eastern and north-eastern parts of Spain and in southern Portugal. Serological effects, such as could derive from the assimilation of a large Jewish population, cannot be identified in the data available. The theory that most Hispano-Moslems and Spanish Jews were of indigenous origin is not gainsaid by the serological data available.

HLA B27 in the population of northern Sweden

The frequency of HLA B27 in blood donors born in northern Sweden was found to be 16.6%. This was significantly higher than in southern Sweden or in caucasians generally, with the exception of Finland. A close genetic relationship has been found between the population of northern Sweden and the Finnish. The higher frequency of HLA B27 is particularly interesting in view of the finding of a higher incidence of rheumatic diseases in northern than in southern Sweden. We also found a surprisingly large number of patients with reactive arthritides and ankylosing spondylitis in the patient registers of the rheumatology department, which further indicated a genetic influence on rheumatic disorders in northern Sweden.

Studies of tuberculosis in man in relation to infection in cattle

A study has been made in Sweden to investigate whether the risk of tuberculous infection and its trend with time in man in different areas were related to varying prevalences of tuberculous infection in cattle. It was found that the level of the infection risk in man was related to the prevalence of tuberculous infection in cattle, varying from 3-4 per cent in 1935 at age 15 in counties with less than 2 per cent infected cattle to 5-8 per cent in counties with 20 per cent infected cattle or more. However, the downward trend to the risk of infection with time was not to found be associated with the prevalence of tuberculous infection in cattle. The correlation between the risk of infection in man and the prevalence of infection in cattle in the 24 Swedish counties was positive and highly significant (+0-79). The relationship between cattle tuberculosis and tuberculosis in man was further studied by correlating infection in cattle with tuberculosis mortality and morbidity in man. The correlation with mortality was negative and highly significant (-0-77), i.e. counties with little cattle tuberculosis had a high tuberculosis mortality in man, and vice versa. There were similar large negative correlations with measures of tuberculosis incidence. When variations between the counties in relevant environmental factors, namely capital, urbanization and overcrowding, were taken into account, a strong positive association remains between the prevalence of infected cattle and the risk of tuberculous infection in man, but the associations with tuberculous mortality and morbidity, though they remain negative, become weaker. It is suggested that the probable explanation of these findings is the long-term protection against adult infection with human tubercle bacilli conferred by bovine infection in childhood.