Elevated serum beta 2-microglobulin levels and C1q-binding immune complexes in sarcoidosis.

Serum beta 2 microglobulin levels were found significantly higher (3.05 +/- 0.98 mg/l) in 32 sarcoidosis patients without renal dysfunction than in normal controls (1.54 +/- 0.22 mg/l). Low levels of C1q-binding immune complexes were detected in 70% of patient's sera, despite the absence of extra-thoracic manifestations. C-reactive protein was detected in 55% of sarcoidosis sera. Neither C1q-binding immune complexes nor C-reactive protein were correlated with beta 2 microglobulin levels. Beta 2 microglobulin raised during relapses and fell under efficient corticosteroid treatment. Beta 2 microglobulin would represent a possible biological marker of disease activity.