Levels of IgD in patients with rheumatoid arthritis.

It has been proposed that IgD may have a pathophysiological role in certain autoimmune diseases, since antinuclear IgD antibodies were revealed in patients with systemic lupus erythematosus, rheumatoid arthritis and systemic sclerodermia. The studies on the problem of evaluation of serum IgD levels in patients with rheumatoid arthritis (RA) are scanty and their results are controversial. We studied IgD levels in patients with RA in order to demonstrate possible correlations with selected immunologic parameters, and to determine the relevance of IgD quantitation in the diagnosis of RA. We determined IgD levels in 30 patients with classic or proven RA, and in 30 age and sex-matched volunteers. Immunoglobulins of A, M, G classes were also determined. E-rosettes were assayed by the method of Jondal et al. in a modification. The distribution of IgD concentrations in donors revealed two modes, and also showed bimodal distributions in the patients. IgG and IgA levels were practically equal in the IgD-positive patients, but IgM was significantly lower than in the IgD-negative subjects. E-rosette values were also different in these subgroups. IgD-positive patients had significantly higher numbers of E-rosettes (1254 +/- 215), compared to IgD-negative individuals (497 +/- 146). IgD was found more often in the seropositive patients to rheumatoid factor (60%) than in seronegative ones (33%) but the difference was not statistically significant.