Phosphatidylserine-dependent anti-prothrombin antibodies (aPS/PT) in infliximab-treated patients with inflammatory bowel diseases

To (1) examine the occurrence and concentrations of aPS/PT and aPL in inflammatory bowel disease (IBD) patients at the beginning of and during anti-TNF-alpha therapy with infliximab; (2) investigate the link of the aPS/PT and aPL presence with antibodies to infliximab (ATI) formation; and (3) examine possible clinical consequences of aPS/PT and/or aPL positivity in IBD patients.

Thirty (30) IBD patients treated with infliximab were analyzed regarding aPS/PT, aPL, and ATI antibody serum levels by standardized ELISAs at treatment weeks 2 (W2) and 14 (W14).

At W2, 40 % of infliximab-treated patients had elevated aPS/PT and 16.7 % had elevated aPL serum levels. At W14, the proportion of aPS/PT-positive sera decreased to 16.6 %, whereas aPL distribution remained unchanged. Moreover, concentrations of aPS/PT have shown significant differences at W2 (16.64 [10.06; 33.06] U for IgG and 18.46 [9.18; 32.48] U for IgM) and at W14 (8.24 [2.78; 19.82] U for IgG and 8.57 [5.55; 26.82] U for IgM), p = 0.009 and p = 0.003, respectively. In ATI-positive samples, aPS/PT IgG were more frequent (p = 0.001 for W2 and p = 0.003 for W14), whereas aPS/PT IgM and aPL IgG/IgM did not show such association.

Higher concentrations of aPS/PT IgG and IgM were found in IBD patients at the beginning of the biological treatment period compared to the maintenance treatment period. Moreover, aPS/PT IgG were more frequent in ATI-positive individuals, which was not observed in aPL. We speculate that there is a relationship between the aPS/PT and the severity of inflammation and auto-aggressive processes in IBD.