Beta2-glycoprotein I (beta2-GPI) mRNA is expressed by several cell types involved in anti-phospholipid syndrome-related tissue damage

Abstract

We report here the expression of beta2-GPI mRNA by cell types involved in the pathophysiology of the anti-phospholipid syndrome (APS), i.e. endothelial cells as a target of autoantibodies in the APS, astrocytes and neurones involved in APS of the central nervous system (CNS). Lymphocytes were also included in the study, as it has been demonstrated that patients with systemic lupus erythematosus-associated CNS diseases have serum anti-lymphocyte antibodies cross-reacting with brain antigens, and intrathecally synthesized anti-neurone antibodies. Reverse transcriptase-polymerase chain reaction followed by restriction enzyme digestion of the product obtained demonstrated the presence of beta2-GPI mRNA in all cell types here tested, cultured both in presence and absence of fetal calf serum. In both culture conditions, the same cell types were immunoreactive to an anti-beta2-GPI MoAb, as determined by indirect immunofluorescence technique. Taken together, these results indicate a direct cell synthesis of beta2-GPI, suggesting an antigenic function of beta2-GPI in the APS, including the CNS disease that occurs in this syndrome.

Fig. 1

Shown are reverse transcriptase-polymerase chain reaction (RT-PCR) products of mRNAs for β₂-GPI (left lanes) and for β-actin (right lanes) from HEpGL2 (1), fibroblasts (2), human umbilical vein endothelial cells (HUVEC) (3), T67 (4), T70 (5), LAN5 (6), and lymphocytes (7). The RT-PCR of RNAs results in amplification of the expected bands: 262 bp for β₂-GPI, 218 bp for β-actin. M, 50-bp DNA ladder.

Fig. 2

Shown are the fragments obtained by digestion with the Alu I restriction enzyme of the reverse transcriptase-polymerase chain reaction (RT-PCR) products of β₂-GPI mRNA from HEpGL2 (a), human umbilical vein endothelial cells (HUVEC) (b), T67 (c), T70 (d), LAN5 (e), lymphocytes (f). M, 50-bp DNA ladder. The two fragments are of the expected molecular length (101 and 161 bp), confirming the specificity of the primers used.

Fig. 3

Shown is the immunoreactivity by the aβ₂-GPI MoAb 1A4 with endothelial cells (human umbilical vein endothelial cells (HUVEC)) (a) astrocytoma line T67 (b), glioma line T70 (c), neuroblastoma line LAN5 (d), all cultured in serum-depleted medium for 3 days, and lymphocytes (e). The aβ₂-GPI binding was revealed by indirect immunofluorescence using a goat anti-mouse conjugated with FITC (left panels). Control techniques were performed on each cell type replacing the aβ₂-GPI with non-immune IgG (right panels). Calibration bar = 25 μm.