Urinary excretion of albumin and beta-2-microglobulin, glomerular filtration rate and immune complexes in serum during infectious mononucleosis.

Immune complexes in serum, urinary excretion of albumin and beta-2-microglobulin were determined in patients with infectious mononucleosis, both during the acute stage of the disease and one month later. At the first examination immune complexes were detected in 8 out of 12 patients, using both the ClqBA and the PP-Lc methods, but had disappeared in all after one month. Urinary excretion was initially increased for albumin in one of 9 and for beta-2-microglobulin in 5 of 9 patients. A significant fall in excretion was noted for beta-2-microglobulin during the acute phase (0.486 to 0.190 ng/min (medians), p less than 0.01) whereas albumin excretion did not change significantly (9.0 to 4.0 micrograms/min). Excretions were normal in all patients after one month. The magnitude of proteinuria was not correlated to the serum level of immune complexes. Serum beta-2-microglobulin was initially increased in 8 of 9 patients, but normal after one month (3.8 to 2.2 mg/l, p less than 0.01). There was a significant correlation between levels of beta-2-microglobulin in serum and urine (rho = 0.833, n = 9, p less than 0.01). 51Cr-EDTA clearance was the same during the acute illness and one month later. It is concluded that the abnormalities in urinary protein excretion do not seem to be related to the presence of circulating immune complexes in infectious mononucleosis and that the elevated urinary beta-2-microglobulin excretion is most likely due to increase production.