ANALYSIS OF IMMUNOGLOBULINS IN SARCOIDOSIS

Background: Assessment of local immunoglobulin(Ig)-production in sarco idosis may be indicative of disease activity. However, in interstitial lung disease an increase in protein leakage across the alveolar-capil lary membrane complicates determination of local Ig-production. In ord er to overcome this problem, techniques successfully used for the eval uation of local Ig-production in cerebrospinal fluid were applied to b ronchoalveolar lavage (BAL)-analysis. Methods: Ten patients with biops y-proven sarcoidosis, seven patients with respiratory infections and t en patients as controls without any sign of interstitial lung disease or infection underwent BAL. Equal amounts of total protein (2 mu g/lan e) from BAL and serum samples were run on SDS-PAGE gradient-gel and bl otted to a nitro-cellulose membrane. The blots were stained for total protein, IgA, IgM, IgG and IgG(1-4)-subgroups. Results: Densitometric analysis revealed a significant increase of the IgG/albumin-ratio in B AL of sarcoidosis patients compared to the control,group. In all contr ol patients a single IgG band of identical molecular weight was detect ed both in serum and BAL. In sarcoidosis and pneumonia the serum showe d multiple bands distinct from the BAL-band in regard to molecular wei ght. Subclass analysis of this group revealed an increased band intens ity and different molecular weight of IgG(1), IgG(2) and IgG(4)-bands in BAL compared to serum indicative of local production. IgA and IgM w ere detected in all samples without any significant differences betwee n the three groups. Conclusions: Molecular weight analysis of IgG-subg roups revealed local production of IgG(1,2+4) in sarcoidosis and respi ratory infection. This technique may prove useful with regard to the a ssessment of disease activity in sarcoidosis.