Immunologic characteristics of the leukocyte adherence inhibition assay in rheumatoid arthritis

Peripheral blood leukocytes (PBL) from patients with rheumatoid arthritis (RA) when used in the leukocyte adherence inhibition (LAI) assay were capable of distinguishing antigenic differences between RA and osteoarthritic (OA) synovial membrane extracts. Normal PBL from control subjects with nonadherence index (NAI) values of 7 +/- 2 were able to respond positively (NAI values of 31 +/- 6) in the LAI assay if briefly preincubated with IgG obtained from LAI-position RA subjects. The LAI-positive response of PBL from RA patients was negated by preincubating the cells with sera obtained from LAI-nonreactive RA patients. Preincubation of reactive LAI-positive RA cells with urinary protein from 4 LAI-nonreactive RA patients blocked the response of reactive RA leukocytes in the LAI assay (42 +/- 2 to 14 +/- 2). In contrast, preincubation of reactive LAI-positive RA cells with urinary protein from LAI-reactive RA patients or patients with gout had no effect on subsequent LAI reactivity. This study suggests that LAI-nonreactive RA subjects have a 'rheumatoid neoantigen-like material' in their circulation which is excreted in their urine and is capable of being recognized by PBL of reactive, LAI-positive RA patients.