Antibodies to nucleic acids in systemic lupus erythematosus and rheumatoid arthritis patients and their relatives

DNA and heparin alter the internalization process of anti-DNA monoclonal antibodies according to patterns typical of both the charged molecule and the antibody

The internalization into CHO-K1 fibroblasts of three polyreactive monoclonal IgG2a anti-DNA autoantibodies (mAbs), F14.6, J20.8 and F4.1, isolated from the same unimmunized (NZBxNZW) F1 mouse, and synthetic peptides derived from F4.1 was studied using a technique which quantifies nuclear accumulation. The localization of the mAbs was intranuclear. We compared the influence of two negatively-charged molecules, DNA or heparin. At low concentrations, DNA had dual effects-inhibitory or stimulatory-depending on the mAb. Heparin was inhibitory or had no effect. The possibility that proteoglycans are 'receptors' recognized by anti-DNA mAbs which bind through heparin-sensitive reactions, was explored. Only F4.1 internalization was partly inhibited in glycosaminoglycan-deficient cells. We propose that the complex alterations of internalization patterns of these polyreactive mAbs by the two negatively charged molecules can be explained by (a) the potential of polyreactive mAbs to bind to various charge (or conformation-) dependent 'receptors', (b) the potential of a subclass of mAbs complexed with DNA to utilize additional 'receptor(s)'. Glycosaminoglycans were required for internalization of F4.1-derived peptides, which remained extranuclear, suggesting that nuclear internalization of mAb F4.1 is a multistep process that requires certain sequences present on the intact mAb.

Soluble HLA-I in rheumatic diseases

OBJECTIVE

To study serum levels of Class I soluble HLA (sHLA-I) in patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), polymyositis or dermatomyositis (PM/DM) or scleroderma and to assess the possible influence of ethnic factors on concentration in each disease group.

METHODS

Solid-phase enzyme linked immunoassay was used to measure sHLA-I in the serum of 385 patients with varied ethnic backgrounds (American-Caucasians, African-Americans, Georgian-Caucasians) with rheumatic diseases. Studies on patients were compared to similar measurements of 189 healthy individuals.

RESULTS

Mean sHLA-I levels were significantly higher in patients with SLE than those observed in healthy individuals or other rheumatic diseases. Highest concentrations were present in Georgian-Caucasian patients with SLE. American-Caucasian patients with RA or scleroderma had higher sHLA-I levels than normal Caucasian individuals. The majority of patients with PM/DM in all ethnic subgroups were low secretors of sHLA-I.

CONCLUSION

Mechanisms underlying the secretion of sHLA-I appear to differ among the rheumatic diseases studied and various ethnic groups. These genetic differences in sHLA-I secretion could be associated with ethnic and pathophysiologic differences among these rheumatic diseases.

Autoantibodies in patients with juvenile chronic arthritis and their immediate family relatives

Antibodies to nuclear antigens were assessed in 23 children with juvenile chronic arthritis (JCA) and 66 of their first degree relatives. Serum samples from 16 patients with JCA (70%) and nine relatives (14%) had antinuclear antibodies by indirect immunofluorescence. Antibodies against nuclear antigens in rabbit thymus extract or an erythroblastoid cell line (K562) were detected by countercurrent immunoelectrophoresis and immunoblotting in 16 patients (70%) and 39 family relatives (59%). Immunoblotting did not show any banding patterns common to all patients with JCA, though bands in the 43-45 kD range were detected in 5/23 patients. Anticardiolipin antibodies were found in 7/23 patients. In total, 18/20 families (90%) had members other than the probands with detectable autoantibodies. In five families immunoblotting showed common banding patterns between the probands and other members. This suggests that there might be an inherited trend towards autoimmune responses in some families of patients with JCA.