CD45 autoantibodies mediate neutralization of activated T cells from lupus patients through anergy or apoptosis

Abstract

The objectives were to provide estimates of the prevalence of autoantibody (Ab) directed to CD45 in lupus patients, identify the target autoantigen(s), and determine the ability of such reactivity to mediate neutralization of T lymphocytes. Sera from 64 patients were studied using 2 assays: Western blot and an ELISA with CD45 eluted from 3 cell lines as antigen (U937, Jurkat and Daudi). The role of carbohydrate specificity was investigated using enzyme digestion of blotted glycans, competition with sugars, and inhibition with lectins. Apoptosis was studied through annexin V binding, and cell cycle analysis using the propidium iodide method. AutoAb to CD45 were detected in 16/64 sera (25%) by Western blot, and 21/32 sera (66%) found positive in the ELISA. CD45 purified from Daudi cells was identified in the ELISA, but not in the blot. AutoAb were of the IgM and the IgG isotypes, but not specific for a particular cell type or CD45 isoform: 2 dominant specificities were recognized, one against p180, and another against high MW isoforms. Neuraminidase-induced enhancement of reactivity, together with the inhibitory effect of N-acetyl galactosamine and Dolichos diflorus lectin suggest that the epitopes are carbohydrates. AutoAb which were specific for activated CD4+T cells triggered the annexin V binding, and, in 2 of 4 cases, lymphocytes underwent apoptosis. In conclusion, carbohydrate conformational epitopes may be important as target antigens, and some CD45 autoAb have the capacity to neutralize activated T cells through anergy or apoptosis.

Involvement of tyrosine phosphatase CD45 in apoptosis

“…These findings agreed with the phenotypes observed in CD45-deficient mice and further substantiate the involvement of CD45 in antigen receptor signaling and T and B cell development [27]. During lupus erythematosus, autoantibodies raised against CD45 that is expressed on T cells but not on B cells are generated, which results in the neutralization of activated T cells through anergy or apoptosis [126,127]. This process appears to be dependant on the glycosylation state of CD45 molecules.…”

Lymphocytotoxic Autoantibodies

“…The MLC assay used for histocompatibility assaying has been adapted to distinguish cold (15 °C) from warm (37 °C) Abs and noncomplement-dependent from complement-dependent Abs [7].…”

Μελέτη Βιομορίων Σε Λεμφοκύτταρα Ασθενών Με Αυτοάνοσα Ρευματικά Νοσήματα

“…Η ADA1 συνδέεται με το CD26 με Κ Α 4-20nM 67 , και τα δύο μόρια συνεκφράζονται και αντιδρούν στην επιφάνεια του Τ λεμφοκυττάρου, όπου και εντοπίζονται. Τα υπολείμματα Leu 294 και η περιοχή από τη Leu 340 ως την Arg 343 (Leu 340 -Val-Ala-Arg 343 ) του CD26 και τα υπολείμματα Glu 139 , Arg 142 , Asp 143 της ADA είναι βασικά για τη σύνδεση των δύο μορίων 68,69 . Το CD26 δεν μεταφέρει την ADA μέσα στο κύτταρο.…”

“…Σε ένα μικρό ποσοστό ασθενών (25%-66% ανάλογα με τη μέθοδο ανίχνευσης) με ΣΕΛ ανιχνεύονται αυτοαντισώματα έναντι του CD45 138 . Κάποια από αυτά τα αντι-CD45 αντισώματα έχουν την ικανότητα να εξουδετερώνουν τα ενεργοποιημένα Τ λεμφοκύτταρα μέσω αδράνιας ή απόπτωσης 139 .…”