Analysis of T cell responses to the beta 2-glycoprotein I-derived peptide library in patients with anti-beta 2-glycoprotein I antibody-associated autoimmunity.

Antiphospholipid syndrome (APS) is an autoimmune disease that accompanies anti-phospholipid antibodies measured as either anti-cardiolipin antibodies (aCL) or lupus anticoagulant. beta(2)-glycoprotein I (beta(2)GPI) is the most common and apparently the best-characterized antigenic target for aCL. To investigate T-cell responses to beta(2)GPI, we stimulated PBMC of 18 APS or systemic lupus erythematosus (SLE) patients carrying anti-beta(2)GPI and 10 healthy controls, using a peptide library covering the beta(2)GPI sequence. We established seven CD4(+) T cell lines reactive with beta(2)GPI peptide. Three of four epitopes for patient-derived T cell lines were p244-264, whereas one T cell line from a control subject also recognized p244-264. Furthermore, there was no tendency for particular HLA class II molecules to present beta(2)GPI peptides. However, cytokine producing patterns were significantly different between T cell lines from patients and those from healthy individuals (p =.028); patients' T cells tend to exhibit higher IL-4 and lower IFN-gamma responses. These T cell lines did not react to beta(2)GPI purified from human plasma. These results indicate that beta(2)GPI-reactive CD4(+) T cells of APS/SLE patients mainly recognize cryptic p244-264 in the context of various HLA class II molecules, and exhibit Th0-Th2-type responses. Our findings may provide a clue to the pathogenesis of APS.